A Beginner's Guide to Delphi Want to learn Delphi programming? You are at the right place!
By Zarko Gajic Delphi Expert About Delphi Programming site proudly presents: free online programming courses for (beginner) Delphi developers! Quick launch:
Turbo Delphi Tutorial: For Novice and Non-Programmers This series of tutorials is oriented to those who want to take their chance in the world of software development, it is designed to teach the complete beginner (read: "non-programmer") how to become a programmer using Delphi.
Delphi for Beginners This free online course is perfect for beginner developers as well as for those who want a broad overview of the art of programming Win32 applications with Borland Delphi. Focus on Delphi 6. Delphi Database Programming. You can take this as an Email Course Developers will learn how to design, develop and test a database application using ADO with Delphi. This course focuses on the most common uses of ADO in a Delphi application: Connecting to a database using TADOConnection, work with Tables and Queries, handle database exception, create reports, etc.
Learning Object Oriented Programming with Delphi Explore the true power of Delphi OOP: learn how to create your own classes, instatiate objects at run time, use association, composition and other OOP topics. Using the TDBGrid component Contrary to most other Delphi data-aware controls, the DBGrid component has many nice features and is more powerful than you would have thought. The "standard" DBGrid does its job of displaying and manipulating records from a dataset in a tabular grid. However, there are many ways (and reasons) why you should consider customizing the look and feel of a DBGrid... Creating Custom Components Everything about creating custom controls and components in Delphi. The ultimate source. From tutorials for starters to more advanced materials. Introduction to COM Programming. You can take this as an Email Course COM stands for Component Object Model. It allows you to create COM objects that are not specific to any language, and in some cases, even platforms. For instance, COM objects can be ported to a Unix system. COM also allows you to create COM
Objects that will be instantiated on a different machine across the world if you so desired.
(Fast Forward to) Delphi for .NET Here's a series of articles designed with one goal in mind: to provide a quick and dirty introduction to the world of .NET programming with Delphi. If you are looking for "what you need to know about Delphi for .NET" - search no further! ASP.NET Web Programming Developers will learn how to design, develop and debug ASP.Net web application using Borland Delphi for .Net. The chapters will cover the fundamental elements of creating Web applications (working with Web Forms, Web Services and User Controls) using Delphi, including the Integrated Development Environment (IDE) and the Delphi for .Net language. Windows API (no VCL) Series This free online course is perfect for intermediate Delphi developers as well as for those who want a broad overview of the art of Windows API programming with Borland Delphi.
Delphi History – from Pascal to Embarcadero Delphi XE 2 This document provides concise descriptions of Delphi versions and its history, along with a brief list of features and notes. Find out how Delphi evolved from Pascal to a RAD tool that can help you solve complex development problems to deliver high-performance, highly scalable applications ranging from desktop and database applications to mobile and distributed applications for the Internet – not only for Windows but also for Linux and the .NET. What is Delphi? Delphi is a high-level, compiled, strongly typed language that supports structured and object-oriented design. Delphi language is based on Object Pascal. Today, Delphi is much more than simply "Object Pascal language". The roots: Pascal and its history The origin of Pascal owes much of its design to Algol - the first high-level language with a readable, structured, and systematically defined syntax. In the late sixties (196X), several proposals for an evolutionary successor to Algol were developed. The most successful one was Pascal, defined by Prof. Niklaus Wirth. Wirth published the original definition of Pascal in 1971. It was implemented in 1973 with some modifications. Many of the features of Pascal came from earlier languages. The case statement, and value-result parameter passing came from Algol, and the records structures were similar to Cobol and PL 1. Besides cleaning up or leaving out some of Algol's more obscure features, Pascal added the capability to define new data types out of simpler existing ones. Pascal also supported dynamic data structures; i.e., data structures which can grow and shrink while a program is running. The language was designed to be a teaching tool for students of programming classes.
In 1975, Wirth and Jensen produced the ultimate Pascal reference book "Pascal User Manual and Report". Wirth stopped its work on Pascal in 1977 to create a new language, Modula the successor to Pascal. Borland Pascal With the release (November 1983) of Turbo Pascal 1.0, Borland started its journey into the world of development environments and tools. To create Turbo Pascal 1.0 Borland licensed the fast and inexpensive Pascal compiler core, written by Anders Hejlsberg. Turbo Pascal introduced an Integrated Development Environment (IDE) where you could edit the code, run the compiler, see the errors, and jump back to the lines containing those errors. Turbo Pascal compiler has been one of the bestselling series of compilers of all time, and made the language particularly popular on the PC platform. In 1995 Borland revived its version of Pascal when it introduced the rapid application development environment named Delphi - turning Pascal into a visual programming language. The strategic decision was to make database tools and connectivity a central part of the new Pascal product. The roots: Delphi After the release of Turbo Pascal 1, Anders joined the company as an employee and was the architect for all versions of the Turbo Pascal compiler and the first three versions of Delphi. As a chief architect at Borland, Hejlsberg secretly turned Turbo Pascal into an objectoriented application development language, complete with a truly visual environment and superb database-access features: Delphi. What follows on the next two pages, is a concise description of Delphi versions and its history, along with a brief list of features and notes.
Delphi versions: from 1 to 5 and counting Now, that we know what Delphi is and where are its roots, it's time to take a trip into the past... Why the name "Delphi"? As explained in the Delphi Museum article, project codenamed Delphi hatched in mid 1993. Why Delphi? It was simple: "If you want to talk to [the] Oracle, go to Delphi". When it came time to pick a retail product name, after an article in Windows Tech Journal about a product that will change the life of programmers, the proposed (final) name was AppBuilder. Since Novell released its Visual AppBuilder, the guys at Borland needed to pick another name; it became a bit of a comedy: the harder people tried to dismiss "Delphi" for the product name, the more it gained support. Once touted as the "VB killer" Delphi has remained a cornerstone product for Borland.
Note: some of the links below marked with an asterix (*), using the Internet Archive WayBackMachine, will take you several years in the past, showing how Delphi site looked long-ago. The rest of the links will point you to a more in-depth look at what each (new) technology is about, with tutorials and articles. Delphi 1 (1995) Delphi, Borland's powerful Windows programming development tool first appeared in 1995. Delphi 1 extended the Borland Pascal language by providing object-orientated and formbased approach, extremely fast native code compiler, visual two-way tools and great database support, close integration with Windows and the component technology. Here's the Visual Component Library First Draft Delphi 1* slogan: Delphi and Delphi Client/Server are the only development tools that provide the Rapid Application Development (RAD) benefits of visual component-based design, the power of an optimizing native code compiler and a scalable client/server solution. Here’s what were the "7 Top Reasons to Buy Borland Delphi 1.0 Client/Server*" Delphi 2 (1996) Delphi 2* is the only Rapid Application Development tool that combines the performance of the world's fastest optimizing 32-bit native-code compiler, the productivity of visual component-based design, and the flexibility of scalable database architecture in a robust object-oriented environment. Delphi 2, beside being developed for the Win32 platform (full Windows 95 support and integration), brought improved database grid, OLE automation and variant data type support, the long string data type and Visual Form Inheritance. Delphi 2: "the Ease of VB with the Power of C++" Delphi 3 (1997) The most comprehensive set of visual, high-performance, client and server development tools for creating distributed enterprise and Web-enabled applications. Delphi 3* introduced new features and enhancements in the following areas: the code insight technology, DLL debugging, component templates, the DecisionCube and TeeChart components, the WebBroker technology, ActiveForms, component packages, and integration with COM through interfaces. Delphi 4 (1998) Delphi 4* is a comprehensive set of professional and client/server development tools for building high productivity solutions for distributed computing. Delphi provides Java interoperability, high performance database drivers, CORBA development, and Microsoft BackOffice support. You've never had a more productive way to customize, manage, visualize and update data. With Delphi, you deliver robust applications to production, on time and on budget.
Delphi 4 introduced docking, anchoring and constraining components. New features included the AppBrowser, dynamic arrays, method overloading, Windows 98 support, improved OLE and COM support as well as extended database support. Delphi 5 (1999) High-productivity development for the Internet Delphi 5* introduced many new features and enhancements. Some, among many others, are: various desktop layouts, the concept of frames, parallel development, translation capabilities, enhanced integrated debugger, new Internet capabilities (XML), more database power (ADO support), etc. Then, in 2000, Delphi 6 was the first tool to fully supports new and emerging Web Services ...
Delphi versions: from 6 to 16 and counting What follows is a concise description of most recent Delphi versions, along with a brief list of features and notes. Delphi 6 (2000) Borland Delphi is the first rapid application development environment for Windows that fully supports new and emerging Web Services. With Delphi, corporate or individual developers can create next-generation e-business applications quickly and easily. Delphi 6 introduced new features and enhancements in the following areas: IDE, Internet, XML, Compiler, COM/Active X, Database support...
What’s more, Delphi 6 added the support for cross-platform development – thus enabling the same code to be compiled with Delphi (under Windows) and Kylix (under Linux). More enhancements included: support for Web Services, the DBExpress engine, new components and classes... Delphi 7 (2001) Borland Delphi 7 Studio provides the migration path to Microsoft .NET that developers have been waiting for. With Delphi, the choices are always yours: you're in control of a complete ebusiness development studio — with the freedom to easily take your solutions cross-platform to Linux. Delphi 8 For the 8th anniversary of Delphi, Borland prepared the most significant Delphi release: Delphi 8 continues to provide Visual Component Library (VCL) and Component Library for Cross-platform (CLX) development for Win32 (and Linux) as well as new features and continued framework, compiler, IDE, and design time enhancements.
Delphi 2005 (part of Borland Developer Studio 2005) Diamondback is the code name of the next Delphi release. The new Delphi IDE supports multiple personalities. It supports Delphi for Win 32, Delphi for .NET and C#... Delphi 2006 (part of Borland Developer Studio 2006) BDS 2006 (code named "DeXter") includes complete RAD support for C++ and C# in addition to Delphi for Win32 and Delphi for .NET programming languages. Turbo Delphi - for Win32 and .Net development Turbo Delphi line of products is a subset of the BDS 2006. CodeGear Delphi 2007 Delphi 2007 released in March 2007. Delphi 2007 for Win32 is primarily targeted at Win32 developers wanting to upgrade their existing projects to include full Vista support - themed applications and VCL support for glassing, file dialogs, and Task Dialog components. Embarcadero Delphi 2009 Embarcadero Delphi 2009. Support for .Net dropped. Delphi 2009 has unicode support, new language features like Generics and Anonymous methods, the Ribbon controls, DataSnap 2009... Embarcadero Delphi 2010 Embarcadero Delphi 2010 released in 2009. Delphi 2010 allows you to create touch based user interfaces for tablet, touchpad and kiosk applications. Embarcadero Delphi XE Embarcadero Delphi XE released in 2010. Delphi 2011, brings many new features and improvements: Built-in Source Code Management, Built-in Cloud Development (Windows Azure, Amazon EC2), Innovative expanded Tool Chest for optimized development, DataSnap Multi-tier Development, much more... Embarcadero Delphi XE 2 Embarcadero Delphi XE 2 released in 2011. Delphi XE2 will allow you to: Build 64-bit Delphi applications, Use the same source code to target Windows and OS X, Create GPU-powered FireMonkey (HD and 3D business) application, Extend multi-tier DataSnap applications with new mobile and cloud connectivity in RAD Cloud, Use VCL styles to modernize the look of your applications...
A Beginner's Guide to Delphi Programming Delphi Course. Chapters 1 - 10.
About the Course: This free online course is perfect for beginner developers as well as for those who want a broad overview of the art of programming with Borland Delphi. Developers will learn how to design, develop and test application using Borland Delphi. The chapters will cover the fundamental elements of creating Windows applications using Delphi, including the Integrated Development Environment (IDE) and the Object Pascal language.
Developers will get up to speed quickly through real world, practical examples. This course is aimed to those who are new to programming, come from some other development environment (like MS Visual Basic, or Java) or are new to Delphi.
Prerequisites: Readers should have at least a working knowledge of the Windows operating system.
Chapters The chapters of this course are being created and updated dynamically on this site. You can find the latest chapter on the last page of this article. Start with Chapter 1 : Introducing Borland Delphi Then continue learning, this course already has more than 18 chapters The chapters of this course are being created and updated dynamically on this site. Chapters (for now) include: CHAPTER 1: Introducing Borland Delphi What is Borland Delphi? Where to download a free version, how to install and configure it. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 2: A journey through the Delphi IDE A quick journey through the main parts and tools of the Delphi integrated development
environment. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 3: Creating your first *Hello World* Delphi Application An overview of application development with Delphi, including creating a simple project, writing code, compiling and running a project. Also, find out how to ask Delphi for help. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 4: Learn about: properties, events and Delphi Pascal Create your second simple Delphi application allowing you to learn how to place components on a form, set their properties, write event handler procedures to make components cooperate together. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 5: Understanding the Delphi unit source Take a closer look at exactly what each keyword means by examining each line of the Delphi form unit source code. Interface, implementation, uses and other keywords explained in easy language! Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 6: An introduction to Delphi Pascal Before you start developing more sophisticated applications by using the RAD features of Delphi, you should learn the basics of the Delphi Pascal language. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 7: Sophisticated Delphi Pascal techniques for Beginners Time to extend your Delphi Pascal knowledge to the max. Here are some intermediate Delphi problems and articles for everyday development tasks. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 8: Commenting Delphi code Learn the art of helping yourself, when it comes to code maintenance. The purpose of adding comments to Delphi code is to provide more program readability using understandable description of what your code is doing. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 9: Cleaning your Delphi code errors A discussion on Delphi design, run and compile time errors and how to prevent them. Also, take a look at some solutions to most common logic errors. Discuss about questions, comments, problems and solutions related to this chapter!
CHAPTER 10: Your First Delphi Game: Tic Tac Toe Designing and developing a real game using Delphi: Tic Tac Toe. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 11: Your First MDI Delphi Project Learn how to create a powerful "multiple document interface" application using Delphi. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 12: Win a copy of Mastering Delphi 7 Delphi Programming Tic Tac Toe Contest - develop your own version of the TicTacToe game and win one copy of the great Mastering Delphi 7 book. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 13: Code Completion in Delphi It's time to learn how to let Delphi help you code faster: start using code templates, code insight, code completion, shortcut keys, ... Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 14: Making Forms Work - a Primer In just about every Delphi application, we use forms to present and retrieve information from users. Delphi arms us with a rich array of visual tools for creating forms and determining their properties and behavior. We can set them up at design time using the property editors and we can write code to re-set them dynamically at runtime. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 15: Communicating Between Forms In "Making Forms Work - a Primer" we looked at simple SDI forms and considered some good reasons for not letting your program auto-create forms. This chapter builds on that to demonstrate techniques available when closing modal forms and how one form can retrieve user input or other data from a secondary form. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 16: Creating flat (non-relational) databases with no database components Delphi Personal edition does not offer database support. In this chapter, you will find out how to create your own *flat* database and store any kind of data - all without a single data aware component. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 17: Working with units While developing a (large) Delphi application, as program becomes more complex, its
source code can become very hard to maintain. In this article you will learn about creating your own code modues - Delphi code files that contain logically associated functions and procedures. Along the process we'll briefly discuss using Delphi's built-in routines and how to make all the units of a Delphi application cooperate. Discuss about questions, comments, problems and solutions related to this chapter! CHAPTER 18: Code navigation in Delphi How to be even more productive with Delphi IDE (precisely, the code editor): start using code navigation features - quickly jump from a method implementation and a method declaration, locate a variable declaration using tooltip symbol insight features, and more. Discuss about questions, comments, problems and solutions related to this chapter!
Introducing Borland Delphi Page 1: What is Borland Delphi? Welcome to the first chapter of the FREE online programing course: A Beginner’s Guide to Delphi Programming. What is Borland Delphi? Where to download a free version, how to install and configure it. What is Borland Delphi? Borland Delphi is a sophisticated Windows programming environment, suitable for beginners and professional programmers alike. Using Delphi you can easily create selfcontained, user friendly, highly efficient Windows applications in a very short time - with a minimum of manual coding. Delphi provides all the tools you need to develop, test and deploy Windows applications, including a large number of so-called reusable components. Borland Delphi, in it's latest version, provides a cross platform solution when used with Borland Kylix - Borland's RAD tool for the Linux platform. Delphi's roots lie in Borland's Turbo Pascal, introduced in the mid-1980s. Object Pascal, the object-oriented extensions to Pascal, is the underlying language of Delphi. The Visual Component Library, or VCL, is a hierarchy of Object Pascal objects that allow you to design applications. A better way of describing Delphi is an Object Pascal-based visual development environment. Delphi editions The latest version of Delphi (in the moment of writing this chapter), version 6, comes in three different editions:
Delphi Personal - makes learning to develop non-commercial Windows applications fast and fun. Delphi 6 Personal makes learning Windows development easy with drag-and-drop visual programming. Delphi Professional - adds the tools necessary to create applications with the latest Windows® ME/2000 look-and-feel. Dramatically enhance functionality with minimal code using the power and flexibility of SOAP and XML to easily integrate Web Services into client-side applications. Delphi Enterprise - includes additional tools, extensive options for Internet. Delphi
6 makes next-generation e-business development with Web Services a snap. This Course will concentrate on the Personal edition. The Personal edition can be downloaded from Borland site. This edition is perfect for beginners since it is free for non-commercial use. As you will see through this Course, Windows development is easy with Delphi Personal 6 drag-and-drop visual design environment, step-by-step examples, and a Visual Component Library with over 85 reusable components. Of course, if you already have a Delphi 6 CD (Professional or Enterprise) you are welcome to join this Course. Note: To purchase fully licensed versions of Borland products visit: http://shop.borland.com/ Warning! The latest Delphi version is Delphi 2009.
Introducing Borland Delphi Page 2: Where to download FREE Delphi 6 Personal Downloading an installing Delphi 6 Personal Delphi 6 Personal system requirements ·Intel Pentium 166 MHz or higher (P2 400 MHz recommended) ·Microsoft Windows 2000, Windows Me, Windows 98, or Windows NT 4.0 with Service Pack 5 or later ·32 Mb RAM (128 Mb recommended) ·75 Mb hard disc space (compact install) ·160 Mb hard disc space (full install) ·VGA or higher resolution monitor ·Mouse or other pointing device
Note: this article describes an old version of Delphi. It is possible that this version is no longer supported! As stated before, the Personal edition of Delphi 6 is freely downloadable from Borland site. Go to Delphi 6 Personal Edition download page, and follow the 3 steps to obtain your serial number, authorization key and then proceed to download. First, you'll need to create a software registration account at Borland - if you already don't have one. Second, you'll be asked to answer a brief survey. And finally, you are allowed to download Delphi 6 Personal and receive your serial number and authorization key via email.
When you get to the download page click on the BorlandDelphiPersonalEdition.EXE link to start the download. Save the file BorlandDelphiPersonalEdition.EXE to your hard drive. After downloading, run BorlandDelphiPersonalEdition.EXE to unpack the installation files.
Note: In the "Borland Delphi Personal Installer" you'll find several interesting folders. In the
\Documentation folder you'll find three PDF files. Developers Guide, Quick Start and Object Pascal Language Guide. You'll be using those books frequently. In the \Info\Extras there are several great tools and components. For example, the \Info\Extras\SendKeys includes two functions that simulate popular Visual Basic routines: Sendkeys and AppActivate. Installation To install Delphi 6 Personal, after you have unpacked the installation files, run INSTALL.EXE (default location C:\Program Files\Borland Delphi Personal Installer) and follow the installation instructions. You are prompted to select a product to install, you only have one choice "Delphi 6":
While the setup runs, you'll need to enter your serial number and the authorization key (the one you got from Borland in your email box).
Later, the License Agreement screen will popup:
Note: Here is a scrap from the LICENSE TERMS FOR THE WORKS YOU CREATE USING BORLAND DELPHI PERSONAL VERSION 6 You may not use the Software for any commercial, business, governmental or institutional purpose of any kind ("Noncommercial Purposes"). Borland grants to you as an individual, a personal, nonexclusive license to install and use the Software for the sole purposes of
designing, developing and running, in source and compiled form, the works which you create for your own personal Noncommercial Purposes, using the Software ("Works"), subject to the restrictions in this License Agreement. You may distribute your Works to others. You may not receive any direct or indirect compensation for the distribution or use of your Works. After that, you have to pick the Setup Type, choose Typical. This way Delphi 6 Personal will be installed with the most common options. The next screen prompts you to choose the Destination folder.
At the end of the installation process, the set-up program will create a sub menu in the Programs section of the Start menu, leading to the main Delphi 6 Personal program plus some additional tools.
Note: For a faster access to Delphi, create a shortcut on the Windows Desktop.
Introducing Borland Delphi Page 3: Starting Borland Delphi Running Delphi for the first time You can start Delphi in a similar way to most other Windows applications:
Choose Programs | Borland Delphi 6 | Delphi 6 from the Windows Start menu Choose Run from the Windows Start menu and type Delphi32 Double-click Delphi32.exe in the $(DELPHI)\Bin folder. Where $(DELPHI) if a folder where Delphi was installed. The default is C:\Program Files\Borland\Delphi6. Double-click the Delphi icon on the Desktop (if you've created a shortcut)
Registering Delphi 6 Personal The first time you run Delphi 6, you'll need to register your copy. Since you've downloaded the Software from Borland site, use the option to register through your web browser:
This will lead you to the Borland web site, where you will need to enter your registration information. In the last step you'll obtain the Activation Key.
And finally, you have run your copy of Delphi 6 Personal for the first time.
Update Pack After you've successfully installed Delphi Personal I suggest you to obtain the latest Update. For the moment, Update Pack 2 is available for registered users (which you are now) from this page: Delphi 6 Downloads. After installation, proceed to download Delphi Personal Documentation Update.
To the next chapter: A Beginner's Guide to Delphi Programming This is the end of the first chapter, in the second chapter, we'll take a quick tour of the main parts and tools of the Delphi IDE - integrated desktop environment. If you need any kind of help at this point, please post to the Delphi Programming Forum where all the questions are answered and beginners are treated as experts.
A journey through the Delphi IDE Page 1: Main menu, Toolbar, Component palette Welcome to the second chapter of the FREE online programming course: A Beginner’s Guide to Delphi Programming. A quick journey through the main parts and tools of the Delphi integrated development environment. The Delphi IDE As explained in the first chapter of this course, one of the ways to start Delphi is to
choose Programs | Borland Delphi 6 | Delphi 6 from the Windows Start menu. When Delphi starts (it could even take one full minute to start - depending on your hardware performance) you are presented with the IDE: the user interface where you can design, compile and debug your Delphi projects.
Like most other development tools (and unlike other Windows applications), Delphi IDE comprises a number of separate windows. The menus, toolbars
The main window, positioned on the top of the screen, contains the main menu, toolbar and Component palette. The title bar of the main window contains the name of the current project (you'll see in some of the future chapters what exactly is a Delphi project). The menu bar includes a dozen drop-down menus - we'll explain many of the options in these menus later through this course. The toolbar provides a number of shortcuts to most frequently used operations and commands - such as running a project, or adding a new form to a project. To find out what particular button does, point your mouse "over" the button and wait for the tooltip. As you can see from the tooltip (for example, point to [Toggle Form/Unit]), many toolbuttons have keyboard shortcuts ([F12]). The menus and toolbars are freely customizable. I suggest you to leave the default arrangement while working through the chapters of this course. The Component Palette
You are probably familiar with the fact that any window in a standard Windows application contains a number of different (visible or not to the end user) objects, like: buttons, text boxes, radio buttons, check boxes etc. In Delphi programming terminology such objects are called controls (or components). Components are the building blocks of every Delphi application. To place a component on a window you drag it from the component palette. Each component has specific attributes that enable you to control your application at design and run time. Depending on the version of Delphi (assumed Delphi 6 Personal through this course), you start with more than 85 components at your disposal - you can even add more components later (those that you create or from a third party component vendor). The components on the Component Palette are grouped according to the function they perform. Each page tab in the Component palette displays a group of icons representing the components you can use to design your application interface. For example, the Standard and Additional pages include controls such as an edit box, a button or a scroll box. To see all components on a particular page (for example on the Win32 page) you simply click the tab name on the top of the palette. If a component palette lists more components that can be displayed on a page an arrow will appear on a far right side of the page allowing you to click it to scroll right. If a component palette has more tabs (pages) that can be displayed, more tabs can be displayed by clicking on the arrow buttons on the right-hand side.
A journey through the Delphi IDE Page 2: Object Inspector, TreeView, Form window, Code explorer Form1 window
Each time you start Delphi, a new project is created that consists of one *empty* window. A typical Delphi application, in most cases, will contain more than one window those windows are referred to as forms. In our case this form has a name, it is called Form1. This form can be renamed, resized and moved, it has a caption and the three standard minimize, maximize and close buttons. As you can see a Delphi form is a regular Windows window. Unit1.pas - the Code Editor window
If the Form1 is the active window and you press [F12], the Code Editor window will be placed on top. As you design user interface of your application, Delphi automatically generates the underlying Object Pascal code. More lines will be added to this window as you add your own code that drives your application. This window displays code for the current form (Form1); the text is stored in a (so-called) unit - Unit1. You can open multiple files in the Code Editor. Each file opens on a new page of the Code editor, and each page is represented by a tab at the top of the window. The Object Inspector Each component and each form, has a set of properties - such as color, size, position, caption - that can be modified in the Delphi IDE or in your code, and a collection of events - such as a mouse click, keypress, or component activation - for which you can specify some additional behavior. The Object Inspector displays the properties and events (note the two tabs) for the selected component and allows you to change the property value or select the response to some event. For example, each form has a Caption (the text that appears on it's title bar). To change the caption of Form1 first activate the form by clicking on it. In the Object Inspector find the property Caption (in the left column), note that it has the 'Form1' value (in the right column). To change the caption of the form simply type the new text value, like 'My Form' (without the single quotes). When you press [Enter] the caption of the form will change to My Form. Note that some properties can be changed more simply, the position of the form on the screen can be set by entering the value for the Left and Top properties - or the form can be simply dragged to the desired location. The Object TreeView Above the Object Inspector you should see the Object TreeView window. For the moment it's display is pretty simple. As you add components to the form, you'll see that it displays a component's parent-child relationships in a tree diagram. One of the great features of the Object TreeView is the ability to drag and drop components in order to change a component container without losing connections with other components. The Object TreeView, Object Inspector and the Form Designer (the Form1 window) work cooperatively. If you have an object on a form (we have not placed any yet) and click it, its properties and events are displayed in the Object Inspector and the component
becomes focussed in the Object TreeView. Closing Delphi To stop working in the Delphi IDE, you can point to the File | Exit option in the main menu. If you have made changes to the current project, you'll be asked if you want to save the changes. Since this is the first time we've done some changes to the project in this course, and we do not yet know how a project is saved and what are the options, select [No]. To the next chapter: A Beginner's Guide to Delphi Programming This is the end of the second chapter, in the third chapter, we'll explore the ways of getting help from Delphi: about the Object Pascal, user interface, VCL, ... If you need any kind of help at this point, please post to the Delphi Programming Forum where all the questions are answered and beginners are treated as experts. First page > The Delphi IDE; Main menu, toolbar > Page 1, 2 A Beginner's Guide to Delphi Programming: Next Chapter >> >> Chapter 3: Creating your first *Hello World* Delphi Application
Creating your first 'Hello World' Delphi Application Page 1: Creating a simple project in Delphi. Welcome to the third chapter of the FREE online programming course: A Beginner’s Guide to Delphi Programming. An overview of application development with Delphi, including creating a simple project, writing code, compiling and running a project. Also, find out how to ask Delphi for help. Creating your first 'Hello World' Delphi Application It's time to create a simple example in Delphi now. When you start Delphi, a default project is created with one form. This default project automatically creates a blank form, with its associated unit file and a project file, among others. To get started, from the beginning, close anything that's open by choosing File | Close All from the main menu. Before you create your first Delphi project, you need to know what you want to develop; a DLL, MDI application, SDI application a CLX application (for Linux) or something else. To start without all the bells and whistles we'll create a standard SDI Windows application. Simply point your mouse to File | New and select Application. This creates a new project group with a single application in it.
The new project contains an empty form, a unit (associated with its form), and a project file. As you develop and build your application, new files will be created and added to the project. The project files are listed in the Project Manager window, display it by selecting View | Project Manager from the main Delphi menu. With the Project Manager, you can easily visualize how all your project files are related. If you share files among different projects, using the Project Manager is recommended because you can quickly and easily see the location of each file in the project. Application vs. CLX Application With some versions of Delphi (supposed Delphi 6 Professional or Enterprise), you can build and develop cross platform applications that can be ported to Linux and compiled with Kylix. To develop a CLX application, instead of standard Windows application, you could pick CLX Application from the File | New menu. The Delphi IDE is similar to one when you build Windows applications, except that the Component palette changes dynamically to show the objects that are available for use in Linux CLX applications. Since this course is about Delphi for the Windows platform, we will be exploring Delphi programming from that point of view. However, if you have Kylix and want to join this course you are of course encouraged to do so. Even though, my intention at this stage of this Course, is not to explain differences between CLX (Linux) and VCL (Windows) development you should know that there are no reasons why you should not join the course and just have in mind that when we talk about, let's say, form1.DFM you think form1.XFM.
Creating your first 'Hello World' Delphi Application Page 2: Writing code, compiling and running your application for the first time. Hello Delphi Now that we've created a project, we can begin work on our first application. This first application will be pretty simple - we'll change the caption of the (main) form once the application is executed. The change will be initiated from code - no user interaction will be necessary. To add the code that changes the caption of the form we need to *call* the Code Editor window. If you have the Project Manager displayed on the screen, double click the Form1. This will bring up the Form designer window to the front. Another way to bring the Form1 to the front of the screen is to select Form1 from the Window menu. Once Form1 is on top and active, double click it. This action has the following result: the Code editor is positioned on the top of the screen and Delphi creates the skeleton code for the new event handler.
Note: another way of achieving the same result is to activate Form1 in the Object Inspector, select the Events tab and double click in the OnCreate column value. As stated in the second chapter of this course, each form has a collection of events – such as a mouse click, keypress, or component activation – for which you can specify some additional behavior. In this case the event is called OnCreate. This event occurs when the form is created. The skeleton code looks like: procedure TForm1.FormCreate(Sender: TObject); begin //this is where your code goes end For the moment do not get bothered with the meaning of the text you see. Now alter the code so that it looks like: procedure TForm1.FormCreate(Sender: TObject); begin Caption := 'Hello Delphi! ' + DateTimeToStr(Now); end Running a project for the first time To see the results of this action, you need to (successfully) compile and run you project. From the Run menu choose Run or press F9. The compiler will try to build the project and execute your application. If the compiler encounters an error, it displays an Error dialog box. When you choose OK to dismiss the dialog box, the Code editor places the cursor on the line of code containing the error.
Note: if you want to see progress reports while your program compiles, you'll need to check the "Show compiler progress" check box in the "Compiling and running" section on the Preferences page of the Environment Options dialog box. Call this dialog box by selecting Environment Options from the Tools menu.
If everything goes well (it should) your application is executed and you see a blank form on the screen. Note several things. First, the form is blank - there are no dots that make up the
grid you see when designing the form look. Second, there is a new button on the Windows Task Bar - when you point to it you'll see that it has the Project1 caption. Third, the caption of Delphi IDE is changed from "Delphi 6 - Project 1" to "Delphi 6 - Project 1 [Running]". And fourth, most important for us, the caption of the form is Hello Delphi ! + *date and time of the execution*. There is not much you can do with this window, you can move it resize it and finally close it. Every time you (compile and) run this project a form caption will say Hello Delphi with the date and time of the execution. Ok, I know this is not a lot, but be patient - this is your first project - it is not supposed to do something meaningful. If you want a little more, here goes another simpe example.
Creating your first 'Hello World' Delphi Application Page 3: Saving your work. Getting help from Delphi. Saving the project To properly get the job done, you should save the project, along with all its associated files. To save the current form design and its code, select File | Save All from the main menu bar. By default, Delphi opens the Projects folder. I suggest you to create a new folder (inside the Projects folder) for your project. Let's call it "HelloExample". While in the Save As dialog, open the newly created HelloExample folder and save the following files: . save Unit1 as MainUnit.pas . save Project1 as HelloProject.dpr Note 1: When you have saved the unit file, the corresponding form was saved as MainUnit.dfm Note 2: In the Code Editor window, Unit1 is now referred to as MainUnit. Note 3: Since you have saved the project with the *new* name, if you run your application now, the button on the Task Bar will say "HelloProject". Of course the name of the application and the name of the project do not need to be the same, later we will see how to change the name of a Delphi application.
Note, if you open up the HelloExample folder in the Windows Explorer, you should find several files inside it. These are MainUnit.pas, MainUnit.dfm and several others. The most important file inside this folder is the HelloProject.exe. This is your applications executable file, if you double click it you'll execute it. If you want to "install" your application on another machine this is the only file you need to copy. Getting HELP from Delphi Let's stop for the moment to explore ways to get help from Delphi in situations when help is necessary. First of all, Delphi is supplied with extensive documentation. If you do not have
the printed manuals, those that came (as PDF) with the installation will do. As stated in the first chapter of this course, the books include: . Quick Start - a brief introduction to Delphi, . Object Pascal Language Guide - a complete reference to the underlying Delphi programming language, and . Developers Guide - which covers advanced topics, from creating database applications to creating your custom components. Beside printed materials, Delphi holds a great deal of information in the Help system. Even though you'll need to learn how to use it, it is really worth it - there are many code examples to help you understand all the nuts and bolts of Object Pascal programming. What's more, context-sensitive Help is available from nearly every portion of the Code editor. To get context-sensitive Help from the Code editor window simply place the cursor on the property, event, method, procedure or type for which you want Help, then press F1. Try it. Position the mouse cursor inside the word "Caption" in the Code Editor (the word Caption you typed in the only example so far) and hit the F1 key.
Once you press the F1 key, a pop up window will ask you to specify more exactly what you want to know. Here comes the hard part: how in the world you know what topic to pick. The "problem" lies in the fact that, in Delphi, many components have properties of the same name (and behavior). To get the help on Form Caption property you need to pick TControl.Caption. Why TControl, when you are working with Form not something called TControl? Well, for the moment this is hard to explain, let's just say that Form derives from something called Control and that Control has a Caption property. What you will find out is that in general, Caption is used for text that appears as a window title. But how will you know what to pick? There is a solution. Point to Object Inspector, Properties page. Select the property you want to find out about and than press F1. Some exercises for you... Since this Course is an online course, there is much you can do to prepare for the next chapter. At the end of each chapter I'll try to provide several tasks for you to get more familiar with Delphi and the topics we discuss in the current chapter. Here are some exercises for you: 0. Learn about the Name property of the Form object. Note that the Name property should tell you what the form does.
1. Explore the Object Inspector and try to figure what properties relate to the Form positioning on the screen (Left, Top, Width, Height, ...) and what happens when you alter them at design time. 2. Try to change the color of the Form from the Object Inspector (Color property) 3. Learn about the BorderIcons and BorderStyle properties and how they relate to visual representation of the Form at run time. 4. Find what exactly DateTimeToStr is used for. 5. Be sure not to miss the next chapter! To the next chapter: A Beginner's Guide to Delphi Programming This is the end of the third chapter, in the fourth chapter, you'll create a second simple application allowing you to learn hot to place components on a form, set their properties, write evnet handler procedures to make components work together. If you need any kind of help at this point, please post to the Delphi Programming Forum where all the questions are answered and beginners are treated as experts.
Learn about: properties, events and Delphi Pascal Page 1: Placing Components on a Form Welcome to the fourth chapter of the FREE online programming course: A Beginner’s Guide to Delphi Programming. Create your second simple Delphi application allowing you to learn hot to place components on a form, set their properties, write event handler procedures to make components cooperate together. Creating your second Delphi Application In the previous chapter we have created a simple Delphi application without going into details of the Object Pascal language behind all Delphi projects. This time, our task is to create a more complex application that involves several Delphi components - again, the application will be pretty simple. The idea is to help you understand the Delphi Pascal source and how components operate and communicate with their properties, methods and events. To start, run Delphi. As explained, when you run Delphi a new project (application) is created with one blank form. Placing Components on a Form All forms of a Delphi application have one or more components. Components, or objects, usually display information or allow the user to perform an action. For example a Label is used to display static text, an Edit box is used to allow user to input some data, a Button can be used to initiate actions. Any combination of components can be placed on a form, you should remember that Windows is even-driven, while your application is running a user can interact with any component on a form, it is your task, as a programmer, to decide what happens when a user clicks a button or changes a text in an Edit box. As stated before, Delphi supplies a number of components for you to create complex user interfaces. You can find all the components you can place on a form on the Component palette. To place a component on a form, locate its icon on the Palette and double-click it. This action places a component on the active form. Visual representation of most components is set with their set of properties. When you first place a component on a
form, it is placed in a default position, with default width and height. You can change the size and position later, by using the Object Inspector. Note: to remove a component from a form, click on it and press the [Del] key. Later, in this Course, I'll explain what happens to code (if some exists) associated with the component. Your second Delphi application We can now start adding components to a form. Activate the only form in a project, point to the Component palette and select the "Standard" tab. We will add three standard Windows components and write some example code to see how components work together.
Double click the following three components: TLabel : use this component when you want to add some text to a form that the user can't edit. TEdit : standard Windows edit control. Edit controls are used to retrieve text that users type. TButton : use this component to put a standard push button on a form. Using drag-and-drop to rearrange the components to appear on a form similar to:
Note: even though at this stage of the Course, it is not important to create "nicely looking" user interfaces, I strongly encourage you to always try to arrange components on form so they create a user friendly interface. Here are some suggestions and Standards of Screen Design.
Learn about: properties, events and Delphi Pascal Page 2: Changing Component Properties; Writing Code - Events and Event Handlers Changing Component Properties After you place components on a form, you can set their properties with the Object Inspector. The properties are different for each type of component, some properties apply to most components. Altering a component property, changes the way a
component behaves and appears in an application. All the components have a property called "Name". The Name property is very important; it specifies the name of the component as referenced in code. When you first place a component on a form, Delphi will provide a default name for the component: Label1, Edit1, Button1. I suggest you to give your components a meaningful name before writing the code that refers to them. You can do this by changing the value of the Name property in the Object Inspector. Here are some suggestions on how to give names to components. Note: with the last statement in mind, I'll do the opposite. In most cases, I'll leave all the default component names through this Course - just as they appear when you place them on a form. To actually change a component property you first need to activate it - click it to select it - small square handles appear at each corner and in the middle of each side. Another way to select a component is to click its name in the drop down list that appears at the top of the Object Inspector. This list lists all the components on the active form along with their types in the following format: "Name Type". When a component is selected, its properties (and events) are displayed in the Object Inspector. To change the component property click on a property name in the Object Inspector; then either type a new value or select from the drop-down list. For example, change the Caption property for Button1 (I'll refer components by their names) to 'Hello...' (of course without the single quotation marks)
Components have different kinds of properties; some can store a boolean value (True or False), like Enabled. To change a boolean property double click the property value to toggle between the states. Some properties can hold a number (e.g. Width or Left), a string (e.g. Caption or Text) or even a set of "simple valued" properties. When a property has an associated editor, to set complex values, an ellipsis button appears near the property name. For example if you click the ellipsis of the Font property a Font property dialog box will appear. Now, change the Caption (the static text the label displays on the form) of Label1 to 'Your name please:'. Change the Text property (text displayed in the edit box - this text will be changeable at run time) of Edit1 to 'Zarko Gajic' (this is my name, write your name). Writing Code - Events and Event Handlers To really enable components to do something meaningful you have to write some actionspecific code for each component you want to react on user input. Remember: components are building block of any Delphi form, the code behind each component ensures a component will
react on an action. Each Delphi component, beside its properties, has a set of events. Windows as even-led environment requires the programmer to decide how a program will (if it will) react on user actions. You need to understand that Windows is a message-based operating system. System messages are handled by a message handler that translates the message to Delphi event handlers. For instance, when a user clicks a button on a form, Windows sends a message to the application and the application reacts to this new event. If the OnClick event for a button is specified it gets executed. The code to respond to events is contained in Delphi event procedures (event handlers). All components have a set of events that they can react on. For example, all clickable components have an OnClick event that gets fired if a user clicks a component with a mouse. All such components have an event for getting and loosing the focus, too. However if you do not specify the code for OnEnter and OnExit (OnEnter - got focus; OnExit - lost focus) the event will be ignored by your application. To see a list of events a component can react on, select a component and in the Object Inspector activate the Events tab. To really create an event handling procedure, decide on what event you want your component to react, and double click the event name. For example, select the Button1 component, and double click the OnClick event name. Delphi will bring the Code Editor to the top of the screen and the skeleton code for the OnClick event will be created. procedure TForm1.Button1Click(Sender: TObject); begin //this is where your code goes end
Note: For the moment there is no need to understand what all the words in the above code stand for. Just follow along, we'll explain all that in the following chapters. As you will understand more clearly through this course, a procedure must have a unique name within the form. The above procedure, Delphi component event-driven procedure, is named for you. The name consists of: the name of the form (prefixed with T) "TForm", a full stop ".", the component name "Button1", and the event name "Click". For any component there is a set of events that you could create event handlers for. Just creating an event handler does not guarantee your application will do something on the event - you must write some event handling code in the body of the procedure. A few words on Delphi (Object) Pascal The code you write inside event procedures is Pascal code. Object Pascal or Delphi Pascal (as I will mostly call it), a set of object-oriented extensions to standard Pascal, is the language of Delphi. Delphi Pascal enables you to take advantage of object-oriented programming to its fullest. It can be said that Delphi Pascal is to Pascal what C++ is to C. As Delphi was being
developed, new language behavior and keywords were added to deal with the component model. In general, Delphi Pascal is a high-level, compiled, strongly typed language that supports structured and object-oriented design. We'll now write some code for the OnClick event handler of Button1. Alter the above procedure body to: procedure TForm1.Button1Click(Sender: TObject); var s: string; begin s := 'Hello ' + Edit1.Text + ' Delphi welcomes you!'; ShowMessage(s); end;
A few words on Delphi Code completion When you reach to the second line and write "Edit1." wait a little, Delphi will display a list box with all the properties of the edit box you can pick. In general, it lists valid elements that you can select from and add to your code. Here's more info on Delphi Code Insight tools. Now, hit F9 to compile and run your project. When the program starts, click the Button1 ('Hello...'). A message box will pop up saying 'Hello Zarko Gajic, Delphi welcomes you!'. Change the text in the Edit box and hit the Button again...
What follows is a simple explanation of the code that runs this application. Let's see. The first line under the procedure name, var s: string;, declares a string type variable. Variables in Delphi Pascal hold information (values). Variables have to be declared before they can be used. We do this after the var keyword. The first line under the begin keyword, s := 'Hello ' + Edit1.Text + ' Delphi welcomes you!'; sets a value for the variable s. This assignment involves reading a value of the Text property for the Edit component. If you ask Delphi about the Text property of an Edit component, you'll find out that it holds the text string that is displayed in the edit box. That text is of the TCaption type, actually the string type. The last statement, before the end keyword, ShowMessage(s);, is the one that calls the message dialog and sends it the value of variable s - this results in a pop up box your see above. That's it. Again, not too smart, not too hard but serves the purpose. By now you should know how to place components on a form, set their properties and even do a small do-something-
funny Delphi application. Be sure to visit all the links in the above paragraph. Some exercises for you... Since this Course is an online course, there is much you can do to prepare for the next chapter. At the end of each chapter I'll try to provide several tasks for you to get more familiar with Delphi and the topics we discuss in the current chapter. Here are some exercises for you, after you finish reading this chapter: 1. Play with the Color property of the Form object 2. Use the Font property Editor to alter the font of the TLabel component 3. Find out about the PasswordChar property of the TEdit component to create a simple password dialog form 4. Try adding a code for the OnCreate event of a form to make a form appear centered on a screen. Also, make yourself familiar with the Position property of the TForm object. 5. Be sure not to miss the next chapter! To the next chapter: A Beginner's Guide to Delphi Programming This is the end of the fourth chapter, in the fifth chapter, we'll explore the Code Editor window to help you in understanding the source behind the Form widow. If you need any kind of help at this point, please post to the Delphi Programming Forum where all the questions are answered and beginners are treated as experts.
Understanding the Delphi unit source Page 1: Delphi Unit source code Welcome to the fifth chapter of the FREE online programming course: A Beginner's Guide to Delphi Programming. Take a closer look at exactly what each keyword means by examining each line of the Delphi form unit source code. Interface, implementation, uses and other keywords explained in easy language! Understanding the unit source In the previous chapter you have created your second simple Delphi application without going into details about the Delphi Pascal keywords that appear in each Delphi unit. This time, our task is to take a look at exactly what each keyword means by examining each line of the forms unit source code. As you know already by now, forms are visible building blocks of all (well, at least 99%) Delphi projects. Each form in a Delphi project has an associated unit. The unit contains the source code for any event handlers attached to the events of the form or the components it contains. The best way to describe the unit code is to take a look at the source. For the moment reefer to the example in the last chapter, especially the unit source. After we have placed a Label, an Edit box and a Button, and added an OnClick event handling procedure for the button, the source code looked like: 01: unit Unit1; 02: interface
03: uses 03: Windows, Messages, SysUtils, Variants, Classes, 03: Graphics, Controls, Forms, Dialogs, StdCtrls; 04: type 05: TForm1 = class(TForm) 06: Edit1: TEdit; 07: Button1: TButton; 08: Label1: TLabel; 09: procedure Button1Click(Sender: TObject); 10: private 11: { Private declarations } 12: public 13: { Public declarations } 14: end; 15: var 16: Form1: TForm1; 17: implementation 18: {$R *.dfm} 19: 20: 21: 22: 23: 24:
procedure TForm1.Button1Click(Sender: TObject); var s: string; begin s := 'Hello ' + Edit1.Text + ' Delphi welcomes you!'; ShowMessage(s); end;
25: end. We'll now explore and try to figure what each line stands for. First, a note: Delphi units follow a predefined format. For example, the UNIT keyword must be the first line in the source, followed by INTERFACE... This strict format is "predefined" by Delphi, meaning that when you add an empty form to a project, its associated unit source is already created with special keywords and type declaration. When you add a component on a form and write an event handler for it, Delphi will place the corresponding code at the exact location in the unit file. Note another thing: in the above code, black lines appear in the forms unit source the first time you add a form to a project. Lines colored in green were added by Delphi when you have placed those three components on a form. Lines in red were added by you in the previous chapter. Whenever you create a new form, Delphi creates the corresponding unit file with the skeleton code marked black. The rest of the article will discuss parts of the unit source. Several new words like class, object and similar will be mentioned, do not get frightened if you do not understand what they mean, let's just say that such words are a part of Delphi object oriented programming, we will discuss them in the following chapters more clearly.
Understanding the Delphi unit source Page 2: Interface, implementation, uses and other keywords explained in easy language! The UNIT keyword A unit file begins with a unit heading, which is followed by the interface, implementation,
initialization, and finalization sections. The initialization and finalization sections are optional. The unit heading starts with a word unit (line 01), followed by a unit (file) name. The unit name (Unit1 in the above source) must match the unit file name on a disk. In a single project all unit names must be unique. You should change the unit's name only by using the File-Save As command from the Delphi IDE main menu. Of course, it is completely up to you to decide how will you name your units. In most cases you'll want your units to have the name similar to the name of the form to which they are linked, like 'MainUnit' for Main form (form with a Name property set to 'Main'). Be sure to give name to units in the early stage of a form design development. The INTERFACE section The interface section of a unit starts with the word interface (line 02) and continues until the word implementation (line 17). This section is used to declare any public sections of code that appear in a unit. The entire contents of the interface section, including type, variable and procedure declarations, are visible to any other unit which uses this unit. When any other part of the program looks at a unit, all it sees is the interface section. Everything else is hidden, internal to the unit, part of the implementation. You could say that the interface section contains a list of items in the unit that other units can use. In most cases the interface section will define several "subsections", you can see that the code for unit1.pas has a uses clause, a type section, and a variable declaration section. The INTERFACE USES section If the interface section includes a uses clause, it must appear immediately after the word interface. A uses clause (line 03) lists units used by the unit. In most cases, all necessary units are placed in the interface uses clause when Delphi compiler generates and maintains a units source. The Windows, Messages, SysUtils, etc are all standard Delphi units, required by a program. As you drop components on a form, the necessary units will be added automatically to the uses clause. For example, if you add a TOpenDialog component on your form (Dialogs page on the component palette), the Dialogs unit will appear in the uses clause because it contains the logic for the TOpenDialog component (and other Dialog components). In some situations, you'll need to manually add units to interface uses clause. Suppose you are to use the TRegistry object, designed to access the Windows Registry. You cannot drop the TRegistry component on a form, since it does not appear on the component palette - you must manually add the word Registry to the uses list. The INTERFACE TYPE section Another part of the interface section is the type section. The form type declaration (or form class declaration) section introduces the form as a class. The code from line 04 to 14 declares the existence and structure of a class called TForm1. A few words on classes and objects I'm aware that this is not the place to explain OOP in Delphi, but I sense that something must be stated. The basics of object oriented programming in Delphi will be discussed in the next chapter of this course, however some words must be explained now. A class, or class type, defines a structure consisting of fields, methods, and properties. Instances of a class type are called objects. For example, in real world, a class PROGRAMMER can have properties like: Years_Of_Experience and Projects_Developed. It can expose methods like: Write_Program and Talk_To_Users. A class is something that does not truly exists. An
object: DELPHI PROGRAMMER is a specific instance of a class.
The TForm1 is a class inherited from TForm (line 05). Each component dropped on a form becomes a field (or variable) of the TForm1 class (lines 06 through 08). For example, Edit1 is a variable of a TEdit type, which you see on the screen when you run the program. When you need to read a value from this particular edit box you use the Edit1 variable, like in 's := Edit1.Text'. Each event handling procedure for a form events or events for components dropped on a form (form fields) will have its declaration (line 09) in the interface type part. For an explanation on private and public parts (lines 10 through 14) of a class declaration, please refer to Hiding Data, a part of the Creating Custom Delphi Components - Inside and Out article. The INTERFACE VAR section This part (line 15,16) of the interface section is used to declare (create) a Form1 object as an instance of the TForm1 class. If you have created your own data type (with fields, properties and methods) as a part of this unit, you could create a variable of that type in this part of the interface section. The IMPLEMENTATION section The implementation section is defined as everything between the implementation word and either the initialization statement or the end of the file (as denoted by the end. keyword). The implementation is where you write code that performs actions. This section is private to the unit, and can contain both declarations and code. The implementation section of a unit can contain its own uses clause as well. A few words on using another unit (form) As you will see in the following chapters of this course, a (form) unit can use another unit. Simply put, this means that one form can call another form. Suppose you have a main form (form name: MainForm, unit name: MainFormUnit) in a project with an 'About...' button on it. What you want to do is to show an about box form (form name: AboutForm, unit name: AboutFormUnit) when you click on this button. To be able to do this the MainFormUnit must use the AboutFormUnit, the AboutFormUnit should be placed in the implementation uses clause. To actually call a method (procedure or function) from MainFormUnit that is declared in the AboutFormUnit, you use the following syntax: AboutFormUnit.SomeProcedureName(parameters) Note that the call to a procedure SomeProcedureName consists of a unit name (AboutFormUnit) followed by a period (.) and a procedure name. This fact is very important. If in some stage of the development of your project you decide to save AboutFormUnit under a different name - you will need to change the call to any procedure inside that unit, since the name of the unit will no longer be AboutFormUnit. This is the reason why you should give meaningful name to units in the early stage of form (unit) development.
Anything that appears in a unit's implementation section that is not referenced in the interface is private to that unit. This means that a procedure or function declared and
defined (implemented) in the implementation section cannot be called from another unit unless its header is listed in that unit's interface. The INITIALIZATION and FINALIZATION sections These two sections are optional; they are not automatically generated when we create a unit. If we want to initialize any data the unit uses, we can add an initialization code to the initialization section of the unit. When an application uses a unit, the code within the unit's initialization part is called before the any other application code runs. If your unit needs to perform any cleanup when the application terminates, such as freeing any resources allocated in the initialization part; you can add a finalization section to your unit. The finalization section comes after the initialization section, but before the final end. Other units of a Delphi project Now, when you have learned about the structure of a Delphi form unit, it's time to see what other units can appear in a project. Every Delphi program has at least two main parts. The first is a project file such as Project1.dpr. You can see the structure of the project file by pointing you mouse to Project|View Source from the Delphi main menu. The second part is one (or more) units attached to forms - the structure of such a unit is discussed through this article. However, units don't have to be associated with forms. A Code Unit contains code that is called from other units in the project. When you start building libraries of useful routines, you will probably store them in a code unit. To add a new code unit to Delphi application choose File-New ... Unit. The structure of a code unit is similar to form unit, it only lacks the type declaration for the "linked" TForm class. Looking in the past: Code Explorer In the second chapter of this course you have learned the main parts of the Delphi IDE. When we were discussing the Code Editor window, one part of that window was left unexplained - the Code Explorer. By default, the Code Explorer is docked to the left of the Code editor. The Code Explorer makes it easy to navigate through your unit source. The Code Explorer contains a tree diagram that shows all the types, classes, properties, methods, global variables, and global routines defined in your unit. It also shows the other units listed in the uses clause.
Button1Click.
I use the Code explorer to quickly jump to a procedure or type declaration by simply double-clicking on an item name, like
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