Firebase In IOS Programming

Contents FirebaseDatabase Framework Reference ................................................................................................................... 4 FIRDatabaseQuery ......................................................................................................................................................... 4 Attach observers to read data ................................................................................................................................... 4 

-observeEventType:withBlock: ...................................................................................................................... 4

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-observeEventType:andPreviousSiblingKeyWithBlock: ............................................................................. 5

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-observeEventType:withBlock:withCancelBlock: ........................................................................................ 6

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-observeEventType:andPreviousSiblingKeyWithBlock:withCancelBlock: ............................................... 6

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-observeSingleEventOfType:withBlock: ....................................................................................................... 7

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-observeSingleEventOfType:andPreviousSiblingKeyWithBlock: .............................................................. 8

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-observeSingleEventOfType:withBlock:withCancelBlock: ......................................................................... 9

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-observeSingleEventOfType:andPreviousSiblingKeyWithBlock:withCancelBlock: ................................ 9

Detaching observers................................................................................................................................................. 10 

-removeObserverWithHandle: ..................................................................................................................... 10

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-removeAllObservers .................................................................................................................................... 11

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-keepSynced:................................................................................................................................................. 11

Querying and limiting ................................................................................................................................................ 12 

-queryLimitedToFirst:.................................................................................................................................... 12

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-queryLimitedToLast: .................................................................................................................................... 12

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-queryOrderedByChild:................................................................................................................................. 13

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-queryOrderedByKey .................................................................................................................................... 13

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-queryOrderedByValue ................................................................................................................................ 14

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-queryOrderedByPriority .............................................................................................................................. 14

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-queryStartingAtValue: ................................................................................................................................. 15

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-queryStartingAtValue:childKey: ................................................................................................................. 15

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-queryEndingAtValue: .................................................................................................................................. 16

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-queryEndingAtValue:childKey: ................................................................................................................... 17

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-queryEqualToValue: .................................................................................................................................... 17

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-queryEqualToValue:childKey: .................................................................................................................... 18

Properties ................................................................................................................................................................... 19 

ref .................................................................................................................................................................... 19

FirebaseDatabase Framework Reference................................................................................................................. 20 FIRDatabaseReference ............................................................................................................................................... 20 Getting references to children locations ................................................................................................................. 20 

-child: .............................................................................................................................................................. 20

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-childByAppendingPath: ............................................................................................................................... 21

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-childByAutoId ............................................................................................................................................... 21

Writing data................................................................................................................................................................ 22

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-setValue: ....................................................................................................................................................... 22

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-setValue:withCompletionBlock:.................................................................................................................. 22

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-setValue:andPriority: ................................................................................................................................... 23

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-setValue:andPriority:withCompletionBlock: .............................................................................................. 23

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-removeValue ................................................................................................................................................ 24

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-removeValueWithCompletionBlock: .......................................................................................................... 25

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-setPriority: ..................................................................................................................................................... 25

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-setPriority:withCompletionBlock: ............................................................................................................... 26

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-updateChildValues: ..................................................................................................................................... 26

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-updateChildValues:withCompletionBlock: ................................................................................................ 27

Attaching observers to read data ............................................................................................................................ 27 

-observeEventType:withBlock: .................................................................................................................... 28

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-observeEventType:andPreviousSiblingKeyWithBlock: ........................................................................... 28

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-observeEventType:withBlock:withCancelBlock: ...................................................................................... 29

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-observeEventType:andPreviousSiblingKeyWithBlock:withCancelBlock: ............................................. 30

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-observeSingleEventOfType:withBlock: ..................................................................................................... 31

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-observeSingleEventOfType:andPreviousSiblingKeyWithBlock: ............................................................ 32

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-observeSingleEventOfType:withBlock:withCancelBlock: ....................................................................... 32

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-observeSingleEventOfType:andPreviousSiblingKeyWithBlock:withCancelBlock: .............................. 33

Detaching observers................................................................................................................................................. 34 

-removeObserverWithHandle: ..................................................................................................................... 34

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-keepSynced:................................................................................................................................................. 34

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-removeAllObservers .................................................................................................................................... 35

Querying and limiting ................................................................................................................................................ 35 

-queryLimitedToFirst:.................................................................................................................................... 35

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-queryLimitedToLast: .................................................................................................................................... 36

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-queryOrderedByChild:................................................................................................................................. 36

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-queryOrderedByKey .................................................................................................................................... 37

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-queryOrderedByPriority .............................................................................................................................. 38

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-queryStartingAtValue: ................................................................................................................................. 38

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-queryStartingAtValue:childKey: ................................................................................................................. 39

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-queryEndingAtValue: .................................................................................................................................. 39

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-queryEndingAtValue:childKey: ................................................................................................................... 40

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-queryEqualToValue: .................................................................................................................................... 41

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-queryEqualToValue:childKey: .................................................................................................................... 41

Managing presence .................................................................................................................................................. 42 

-onDisconnectSetValue:............................................................................................................................... 42

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-onDisconnectSetValue:withCompletionBlock: ......................................................................................... 43

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-onDisconnectSetValue:andPriority: ........................................................................................................... 43

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-onDisconnectSetValue:andPriority:withCompletionBlock: ..................................................................... 44

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-onDisconnectRemoveValue ....................................................................................................................... 44

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-onDisconnectRemoveValueWithCompletionBlock:................................................................................. 45

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-onDisconnectUpdateChildValues: ............................................................................................................. 45

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-onDisconnectUpdateChildValues:withCompletionBlock:........................................................................ 46

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-cancelDisconnectOperations ..................................................................................................................... 46

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-cancelDisconnectOperationsWithCompletionBlock: ............................................................................... 47

Manual Connection Management ........................................................................................................................... 47 

+goOffline....................................................................................................................................................... 47

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+goOnline....................................................................................................................................................... 48

Transactions .............................................................................................................................................................. 49 

-runTransactionBlock:................................................................................................................................... 49

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-runTransactionBlock:andCompletionBlock:.............................................................................................. 49

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-runTransactionBlock:andCompletionBlock:withLocalEvents: ................................................................ 50

Retrieving String Representation ............................................................................................................................ 51 

-description .................................................................................................................................................... 51

Properties ................................................................................................................................................................... 52 

parent ............................................................................................................................................................. 52

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root .................................................................................................................................................................. 52

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key .................................................................................................................................................................. 53

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URL ................................................................................................................................................................. 53

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database ........................................................................................................................................................ 54

FirebaseDatabase Framework Reference FIRDatabaseQuery @interface FIRDatabaseQuery : NSObject

A FIRDatabaseQuery instance represents a query over the data at a particular location. You create one by calling one of the query methods (queryOrderedByChild:, queryStartingAtValue:, etc.) on a FIRDatabaseReference. The query methods can be chained to further specify the data you are interested in observing

Attach observers to read data



-observeEventType:withBlock: observeEventType:withBlock: is used to listen for data changes at a particular location. This is the primary way to read data from the Firebase Database. Your block will be triggered for the initial data and again whenever the data changes. Use removeObserverWithHandle: to stop receiving updates.

Declaration SW IFT

func observe(_ eventType: DataEventType, with block: @escaping (DataSnapshot) -> Void) -> UInt OBJECTIVE-C

- (FIRDatabaseHandle) observeEventType:(FIRDataEventType)eventType withBlock:(nonnull void (^)(FIRDataSnapshot *_Nonnull))block;

Parameters

eventType

The type of event to listen for.

block

The block that should be called with initial data and updates. It is passed the data as a FIRDataSnapsho

Return Value A handle used to unregister this block later using removeObserverWithHandle:



-observeEventType:andPreviousSiblingKeyWithBlock: observeEventType:andPreviousSiblingKeyWithBlock: is used to listen for data changes at a particular location. This is the primary way to read data from the Firebase Database. Your block will be triggered for the initial data and again whenever the data changes. In addition, for FIRDataEventTypeChildAdded, FIRDataEventTypeChildMoved, and FIRDataEventTypeChildChanged events, your block will be passed the key of the previous node by priority order. Use removeObserverWithHandle: to stop receiving updates.

Declaration SW IFT

func observe(_ eventType: DataEventType, andPreviousSiblingKeyWith block: @escaping (DataSnapshot, String?) -> Void) -> UInt OBJECTIVE-C

- (FIRDatabaseHandle)observeEventType:(FIRDataEventType)eventType andPreviousSiblingKeyWithBlock: (nonnull void (^)(FIRDataSnapshot *_Nonnull, NSString *_Nullable))block;

Parameters eventType

block


The block that should be called with initial data and updates. It is passed the data as a FIRDataSnapshot previous child’s key.

Return Value

A handle used to unregister this block later using removeObserverWithHandle:



-observeEventType:withBlock:withCancelBlock: observeEventType:withBlock: is used to listen for data changes at a particular location. This is the primary way to read data from the Firebase Database. Your block will be triggered for the initial data and again whenever the data changes. The cancelBlock will be called if you will no longer receive new events due to no longer having permission. Use removeObserverWithHandle: to stop receiving updates.

Declaration SW IFT

func observe(_ eventType: DataEventType, with block: @escaping (DataSnapshot) -> Void, withCancel cancelBlock: ((Error) -> Void)? = nil) -> UInt OBJECTIVE-C

- (FIRDatabaseHandle) observeEventType:(FIRDataEventType)eventType withBlock:(nonnull void (^)(FIRDataSnapshot *_Nonnull))block withCancelBlock:(nullable void (^)(NSError *_Nonnull))cancelBlock;


block

cancelBlock


The block that should be called with initial data and updates. It is passed the data as a FIRDataSnaps

The block that should be called if this client no longer has permission to receive these events




-observeEventType:andPreviousSiblingKeyWithBlock:withCancelBlock: observeEventType:andPreviousSiblingKeyWithBlock: is used to listen for data changes at a particular location. This is the primary way to read data from the Firebase Database. Your block

will be triggered for the initial data and again whenever the data changes. In addition, for FIRDataEventTypeChildAdded, FIRDataEventTypeChildMoved, and FIRDataEventTypeChildChanged events, your block will be passed the key of the previous node by priority order. The cancelBlock will be called if you will no longer receive new events due to no longer having permission. Use removeObserverWithHandle: to stop receiving updates.

Declaration SW IFT

func observe(_ eventType: DataEventType, andPreviousSiblingKeyWith block: @escaping (DataSnapshot, String?) -> Void, withCancel cancelBlock: ((Error) -> Void)? = nil) -> UInt OBJECTIVE-C

- (FIRDatabaseHandle)observeEventType:(FIRDataEventType)eventType andPreviousSiblingKeyWithBlock: (nonnull void (^)(FIRDataSnapshot *_Nonnull, NSString *_Nullable))block withCancelBlock: (nullable void (^)(NSError *_Nonnull))cancelBlock;


block

cancelBlock


The block that should be called with initial data and updates. It is passed the data as a FIRDataSnapsh the previous child’s key.





-observeSingleEventOfType:withBlock: This is equivalent to observeEventType:withBlock:, except the block is immediately canceled after the initial data is returned.

Declaration SW IFT

func observeSingleEvent(of eventType: DataEventType, with block: @escaping (DataSnapshot) -> Void) OBJECTIVE-C

- (void)observeSingleEventOfType:(FIRDataEventType)eventType withBlock: (nonnull void (^)(FIRDataSnapshot *_Nonnull))block;


block




The block that should be called. It is passed the data as a FIRDataSnapshot.

-observeSingleEventOfType:andPreviousSiblingKeyWithBlock: This is equivalent to observeEventType:withBlock:, except the block is immediately canceled after the initial data is returned. In addition, for FIRDataEventTypeChildAdded, FIRDataEventTypeChildMoved, and FIRDataEventTypeChildChanged events, your block will be passed the key of the previous node by priority order.

Declaration SW IFT

func observeSingleEvent(of eventType: DataEventType, andPreviousSiblingKeyWith block: @escaping (DataSnapshot, String?) -> Void) OBJECTIVE-C

- (void)observeSingleEventOfType:(FIRDataEventType)eventType andPreviousSiblingKeyWithBlock: (nonnull void (^)(FIRDataSnapshot *_Nonnull, NSString *_Nullable))block;



block



The block that should be called. It is passed the data as a FIRDataSnapshot and the previous child’s ke

-observeSingleEventOfType:withBlock:withCancelBlock: This is equivalent to observeEventType:withBlock:, except the block is immediately canceled after the initial data is returned. The cancelBlock will be called if you do not have permission to read data at this location.

Declaration SW IFT

func observeSingleEvent(of eventType: DataEventType, with block: @escaping (DataSnapshot) -> Void, withCancel cancelBlock: ((Error) -> Void)? = nil) OBJECTIVE-C

- (void) observeSingleEventOfType:(FIRDataEventType)eventType withBlock:(nonnull void (^)(FIRDataSnapshot *_Nonnull))block withCancelBlock:(nullable void (^)(NSError *_Nonnull))cancelBlock;


block

cancelBlock





The block that will be called if you don’t have permission to access this data

observeSingleEventOfType:andPreviousSiblingKeyWithBlock:withCancelBlock: This is equivalent to observeEventType:withBlock:, except the block is immediately canceled after the initial data is returned. In addition, for FIRDataEventTypeChildAdded, FIRDataEventTypeChildMoved, and FIRDataEventTypeChildChanged events, your block will be passed the key of the previous node by priority order. The cancelBlock will be called if you do not have permission to read data at this location.

Declaration SW IFT

func observeSingleEvent(of eventType: DataEventType, andPreviousSiblingKeyWith block: @escaping (DataSnapshot, String?) -> Void, withCancel cancelBlock: ((Error) -> Void)? = nil) OBJECTIVE-C

- (void)observeSingleEventOfType:(FIRDataEventType)eventType andPreviousSiblingKeyWithBlock:(nonnull void (^)(FIRDataSnapshot *_Nonnull, NSString *_Nullable))block withCancelBlock: (nullable void (^)(NSError *_Nonnull))cancelBlock;


block

cancelBlock


The block that should be called. It is passed the data as a FIRDataSnapshot and the previous child’s The block that will be called if you don’t have permission to access this data

Detaching observers



-removeObserverWithHandle: Detach a block previously attached with observeEventType:withBlock:.

Declaration SW IFT

func removeObserver(withHandle handle: UInt) OBJECTIVE-C

- (void)removeObserverWithHandle:(FIRDatabaseHandle)handle;

Parameters handle



The handle returned by the call to observeEventType:withBlock: which we are trying to remove.

-removeAllObservers Detach all blocks previously attached to this Firebase Database location with observeEventType:withBlock:

Declaration SW IFT

func removeAllObservers() OBJECTIVE-C

- (void)removeAllObservers;



-keepSynced: By calling keepSynced:YES on a location, the data for that location will automatically be downloaded and kept in sync, even when no listeners are attached for that location. Additionally, while a location is kept synced, it will not be evicted from the persistent disk cache.

Declaration SW IFT

func keepSynced(_ keepSynced: Bool) OBJECTIVE-C

- (void)keepSynced:(BOOL)keepSynced;

Parameters keepSynced

Pass YES to keep this location synchronized, pass NO to stop synchronization.

Querying and limiting



-queryLimitedToFirst: queryLimitedToFirst: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryLimitedToFirst: will respond to at most the first limit child nodes.

Declaration SW IFT

func queryLimited(toFirst limit: UInt) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryLimitedToFirst:(NSUInteger)limit;

Parameters limit

The upper bound, inclusive, for the number of child nodes to receive events for

Return Value A FIRDatabaseQuery instance, limited to at most limit child nodes.



-queryLimitedToLast: queryLimitedToLast: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryLimitedToLast: will respond to at most the last limit child nodes.

Declaration SW IFT

func queryLimited(toLast limit: UInt) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryLimitedToLast:(NSUInteger)limit;

Parameters limit





-queryOrderedByChild: queryOrderBy: is used to generate a reference to a view of the data that’s been sorted by the values of a particular child key. This method is intended to be used in combination with queryStartingAtValue:, queryEndingAtValue:, or queryEqualToValue:.

Declaration SW IFT

func queryOrdered(byChild key: String) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryOrderedByChild:(nonnull NSString *)key;

Parameters key

The child key to use in ordering data visible to the returned FIRDatabaseQuery

Return Value A FIRDatabaseQuery instance, ordered by the values of the specified child key.



-queryOrderedByKey queryOrderedByKey: is used to generate a reference to a view of the data that’s been sorted by child key. This method is intended to be used in combination with queryStartingAtValue:, queryEndingAtValue:, or queryEqualToValue:.

Declaration SW IFT

func queryOrderedByKey() -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryOrderedByKey;

Return Value A FIRDatabaseQuery instance, ordered by child keys.



-queryOrderedByValue queryOrderedByValue: is used to generate a reference to a view of the data that’s been sorted by child value. This method is intended to be used in combination with queryStartingAtValue:, queryEndingAtValue:, or queryEqualToValue:.

Declaration SW IFT

func queryOrderedByValue() -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryOrderedByValue;

Return Value A FIRDatabaseQuery instance, ordered by child value.



-queryOrderedByPriority queryOrderedByPriority: is used to generate a reference to a view of the data that’s been sorted by child priority. This method is intended to be used in combination with queryStartingAtValue:, queryEndingAtValue:, or queryEqualToValue:.

Declaration SW IFT

func queryOrderedByPriority() -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryOrderedByPriority;

Return Value A FIRDatabaseQuery instance, ordered by child priorities.



-queryStartingAtValue: queryStartingAtValue: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryStartingAtValue: will respond to events at nodes with a value greater than or equal to startValue.

Declaration SW IFT

func queryStarting(atValue startValue: Any?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryStartingAtValue:(nullable id)startValue;

Parameters startValue

The lower bound, inclusive, for the value of data visible to the returned FIRDatabaseQuery

Return Value A FIRDatabaseQuery instance, limited to data with value greater than or equal to startValue



-queryStartingAtValue:childKey: queryStartingAtValue:childKey: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryStartingAtValue:childKey will respond to events at nodes with a value greater than startValue, or equal to startValue and with a key greater than or equal to childKey. This is most useful when implementing pagination in a case where multiple nodes can match the startValue.

Declaration SW IFT

func queryStarting(atValue startValue: Any?, childKey: String?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryStartingAtValue:(nullable id)startValue childKey: (nullable NSString *)childKey;


childKey


The lower bound, inclusive, for the key of nodes with value equal to startValue




-queryEndingAtValue: queryEndingAtValue: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryEndingAtValue: will respond to events at nodes with a value less than or equal to endValue.

Declaration SW IFT

func queryEnding(atValue endValue: Any?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryEndingAtValue:(nullable id)endValue;

Parameters endValue

The upper bound, inclusive, for the value of data visible to the returned FIRDatabaseQuery

Return Value A FIRDatabaseQuery instance, limited to data with value less than or equal to endValue



-queryEndingAtValue:childKey: queryEndingAtValue:childKey: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryEndingAtValue:childKey will respond to events at nodes with a value less than endValue, or equal to endValue and with a key less than or equal to childKey. This is most useful when implementing pagination in a case where multiple nodes can match the endValue.

Declaration SW IFT

func queryEnding(atValue endValue: Any?, childKey: String?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryEndingAtValue:(nullable id)endValue childKey:(nullable NSString *)childKey;

Parameters endValue

childKey


The upper bound, inclusive, for the key of nodes with value equal to endValue




-queryEqualToValue: queryEqualToValue: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryEqualToValue: will respond to events at nodes with a value equal to the supplied argument.

Declaration

SWIFT

func queryEqual(toValue value: Any?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryEqualToValue:(nullable id)value;

Parameters value

The value that the data returned by this FIRDatabaseQuery will have

Return Value A FIRDatabaseQuery instance, limited to data with the supplied value.



-queryEqualToValue:childKey: queryEqualToValue:childKey: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryEqualToValue:childKey will respond to events at nodes with a value equal to the supplied argument and with their key equal to childKey. There will be at most one node that matches because child keys are unique.

Declaration SW IFT

func queryEqual(toValue value: Any?, childKey: String?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryEqualToValue:(nullable id)value childKey:(nullable NSString *)childKey;

Parameters value

childKey


The name of nodes with the right value

Return Value A FIRDatabaseQuery instance, limited to data with the supplied value and the key.

Properties



ref Gets a FIRDatabaseReference for the location of this query.

Declaration SW IFT

var ref: FIRDatabaseReference { get } OBJECTIVE-C

@property (readonly, strong, nonatomic) FIRDatabaseReference *_Nonnull ref;

Return Value A FIRDatabaseReference for the location of this query.

FirebaseDatabase Framework Reference FIRDatabaseReference @interface FIRDatabaseReference : FIRDatabaseQuery

A FIRDatabaseReference represents a particular location in your Firebase Database and can be used for reading or writing data to that Firebase Database location. This class is the starting point for all Firebase Database operations. After you’ve obtained your first FIRDatabaseReference via [FIRDatabase reference], you can use it to read data (ie. observeEventType:withBlock:), write data (ie. setValue:), and to create new FIRDatabaseReferences (ie. child:).

Getting references to children locations



-child: Gets a FIRDatabaseReference for the location at the specified relative path. The relative path can either be a simple child key (e.g. ‘fred’) or a deeper slash-separated path (e.g. ‘fred/name/first’).

Declaration SW IFT

func child(_ pathString: String) -> DatabaseReference OBJECTIVE-C

- (nonnull FIRDatabaseReference *)child:(nonnull NSString *)pathString;

Parameters pathString

A relative path from this location to the desired child location.

Return Value A FIRDatabaseReference for the specified relative path.



-childByAppendingPath: childByAppendingPath: is deprecated, use child: instead.

Declaration SW IFT

func child(byAppendingPath pathString: String) -> DatabaseReference OBJECTIVE-C

- (nonnull FIRDatabaseReference *)childByAppendingPath: (nonnull NSString *)pathString;



-childByAutoId childByAutoId generates a new child location using a unique key and returns a FIRDatabaseReference to it. This is useful when the children of a Firebase Database location represent a list of items. The unique key generated by childByAutoId: is prefixed with a client-generated timestamp so that the resulting list will be chronologically-sorted.

Declaration SW IFT

func childByAutoId() -> DatabaseReference OBJECTIVE-C

- (nonnull FIRDatabaseReference *)childByAutoId;

Return Value A FIRDatabaseReference for the generated location.

Writing data



-setValue: Write data to this Firebase Database location. This will overwrite any data at this location and all child locations. Data types that can be set are:



NSString – @Hello World



NSNumber (also includes boolean) – @YES, @43, @4.333



NSDictionary – @{@key: @value, @nested: @{@another: @value} }



NSArray

The effect of the write will be visible immediately and the corresponding events will be triggered. Synchronization of the data to the Firebase Database servers will also be started. Passing null for the new value is equivalent to calling remove:; all data at this location or any child location will be deleted. Note that setValue: will remove any priority stored at this location, so if priority is meant to be preserved, you should use setValue:andPriority: instead.

Declaration SW IFT

func setValue(_ value: Any?) OBJECTIVE-C

- (void)setValue:(nullable id)value;

Parameters value



The value to be written.

-setValue:withCompletionBlock: The same as setValue: with a block that gets triggered after the write operation has been committed to the Firebase Database servers.

Declaration SW IFT

func setValue(_ value: Any?, withCompletionBlock block: @escaping (Error?, DatabaseReference) -> Void) OBJECTIVE-C

- (void)setValue:(nullable id)value withCompletionBlock:(nonnull void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters value

block




The block to be called after the write has been committed to the Firebase Database servers.

-setValue:andPriority: The same as setValue: with an additional priority to be attached to the data being written. Priorities are used to order items.

Declaration SW IFT

func setValue(_ value: Any?, andPriority priority: Any?) OBJECTIVE-C

- (void)setValue:(nullable id)value andPriority:(nullable id)priority;

Parameters value

priority




The priority to be attached to that data.

-setValue:andPriority:withCompletionBlock:

The same as setValue:andPriority: with a block that gets triggered after the write operation has been committed to the Firebase Database servers.

Declaration SW IFT

func setValue(_ value: Any?, andPriority priority: Any?, withCompletionBlock block: @escaping (Error?, DatabaseReference) -> Void) OBJECTIVE-C

- (void)setValue:(nullable id)value andPriority:(nullable id)priority withCompletionBlock:(nonnull void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters value

priority

block




The priority to be attached to that data.

The block to be called after the write has been committed to the Firebase Database servers.

-removeValue Remove the data at this Firebase Database location. Any data at child locations will also be deleted. The effect of the delete will be visible immediately and the corresponding events will be triggered. Synchronization of the delete to the Firebase Database servers will also be started. remove: is equivalent to calling setValue:nil

Declaration SW IFT

func removeValue() OBJECTIVE-C

- (void)removeValue;



-removeValueWithCompletionBlock: The same as remove: with a block that gets triggered after the remove operation has been committed to the Firebase Database servers.

Declaration SW IFT

func removeValue(completionBlock block: @escaping (Error?, DatabaseReference) -> Void) OBJECTIVE-C

- (void)removeValueWithCompletionBlock: (nonnull void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters block



The block to be called after the remove has been committed to the Firebase Database servers.

-setPriority: Sets a priority for the data at this Firebase Database location. Priorities can be used to provide a custom ordering for the children at a location (if no priorities are specified, the children are ordered by key). You cannot set a priority on an empty location. For this reason setValue:andPriority: should be used when setting initial data with a specific priority and setPriority: should be used when updating the priority of existing data. Children are sorted based on this priority using the following rules: Children with no priority come first. Children with a number as their priority come next. They are sorted numerically by priority (small to large). Children with a string as their priority come last. They are sorted lexicographically by priority. Whenever two children have the same priority (including no priority), they are sorted by key. Numeric keys come first (sorted numerically), followed by the remaining keys (sorted lexicographically). Note that priorities are parsed and ordered as IEEE 754 double-precision floating-point numbers. Keys are always stored as strings and are treated as numbers only when they can be parsed as a 32-bit integer

Declaration

SWIFT

func setPriority(_ priority: Any?) OBJECTIVE-C

- (void)setPriority:(nullable id)priority;

Parameters priority



The priority to set at the specified location.

-setPriority:withCompletionBlock: The same as setPriority: with a block that is called once the priority has been committed to the Firebase Database servers.

Declaration SW IFT

func setPriority(_ priority: Any?, withCompletionBlock block: @escaping (Error?, DatabaseReference) -> Void) OBJECTIVE-C

- (void)setPriority:(nullable id)priority withCompletionBlock:(nonnull void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters priority

block



The priority to set at the specified location.

The block that is triggered after the priority has been written on the servers.

-updateChildValues: Updates the values at the specified paths in the dictionary without overwriting other keys at this location.

Declaration SW IFT

func updateChildValues(_ values: [AnyHashable : Any]) OBJECTIVE-C

- (void)updateChildValues:(nonnull NSDictionary *)values;

Parameters values



A dictionary of the keys to change and their new values

-updateChildValues:withCompletionBlock: The same as update: with a block that is called once the update has been committed to the Firebase Database servers

Declaration SW IFT

func updateChildValues(_ values: [AnyHashable : Any], withCompletionBlock block: @escaping (Error?, DatabaseReference) -> Void) OBJECTIVE-C

- (void)updateChildValues:(nonnull NSDictionary *)values withCompletionBlock: (nonnull void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters values

block

A dictionary of the keys to change and their new values

The block that is triggered after the update has been written on the Firebase Database servers

Attaching observers to read data



-observeEventType:withBlock: observeEventType:withBlock: is used to listen for data changes at a particular location. This is the primary way to read data from the Firebase Database. Your block will be triggered for the initial data and again whenever the data changes. Use removeObserverWithHandle: to stop receiving updates.

Declaration SW IFT

func observe(_ eventType: DataEventType, with block: @escaping (DataSnapshot) -> Void) -> UInt OBJECTIVE-C

- (FIRDatabaseHandle) observeEventType:(FIRDataEventType)eventType withBlock:(nonnull void (^)(FIRDataSnapshot *_Nonnull))block;


block


The block that should be called with initial data and updates. It is passed the data as a FIRDataSnapsho




-observeEventType:andPreviousSiblingKeyWithBlock: observeEventType:andPreviousSiblingKeyWithBlock: is used to listen for data changes at a particular location. This is the primary way to read data from the Firebase Database. Your block will be triggered for the initial data and again whenever the data changes. In addition, for FIRDataEventTypeChildAdded, FIRDataEventTypeChildMoved, and FIRDataEventTypeChildChanged events, your block will be passed the key of the previous node by priority order. Use removeObserverWithHandle: to stop receiving updates.

Declaration SW IFT

func observe(_ eventType: DataEventType, andPreviousSiblingKeyWith block: @escaping (DataSnapshot, String?) -> Void) -> UInt OBJECTIVE-C

- (FIRDatabaseHandle)observeEventType:(FIRDataEventType)eventType andPreviousSiblingKeyWithBlock: (nonnull void (^)(FIRDataSnapshot *_Nonnull, NSString *_Nullable))block;


block


The block that should be called with initial data and updates. It is passed the data as a FIRDataSnapshot previous child’s key.




-observeEventType:withBlock:withCancelBlock: observeEventType:withBlock: is used to listen for data changes at a particular location. This is the primary way to read data from the Firebase Database. Your block will be triggered for the initial data and again whenever the data changes. The cancelBlock will be called if you will no longer receive new events due to no longer having permission. Use removeObserverWithHandle: to stop receiving updates.

Declaration SW IFT

func observe(_ eventType: DataEventType, with block: @escaping (DataSnapshot) -> Void, withCancel cancelBlock: ((Error) -> Void)? = nil) -> UInt OBJECTIVE-C

- (FIRDatabaseHandle) observeEventType:(FIRDataEventType)eventType withBlock:(nonnull void (^)(FIRDataSnapshot *_Nonnull))block withCancelBlock:(nullable void (^)(NSError *_Nonnull))cancelBlock;


block

cancelBlock


The block that should be called with initial data and updates. It is passed the data as a FIRDataSnaps





-observeEventType:andPreviousSiblingKeyWithBlock:withCancelBlock: observeEventType:andPreviousSiblingKeyWithBlock: is used to listen for data changes at a particular location. This is the primary way to read data from the Firebase Database. Your block will be triggered for the initial data and again whenever the data changes. In addition, for FIRDataEventTypeChildAdded, FIRDataEventTypeChildMoved, and FIRDataEventTypeChildChanged events, your block will be passed the key of the previous node by priority order. The cancelBlock will be called if you will no longer receive new events due to no longer having permission. Use removeObserverWithHandle: to stop receiving updates.

Declaration SW IFT

func observe(_ eventType: DataEventType, andPreviousSiblingKeyWith block: @escaping (DataSnapshot, String?) -> Void, withCancel cancelBlock: ((Error) -> Void)? = nil) -> UInt OBJECTIVE-C

- (FIRDatabaseHandle)observeEventType:(FIRDataEventType)eventType andPreviousSiblingKeyWithBlock: (nonnull void (^)(FIRDataSnapshot *_Nonnull,

NSString *_Nullable))block withCancelBlock: (nullable void (^)(NSError *_Nonnull))cancelBlock;


block

cancelBlock


The block that should be called with initial data and updates. It is passed the data as a FIRDataSnapsh the previous child’s key.





-observeSingleEventOfType:withBlock: This is equivalent to observeEventType:withBlock:, except the block is immediately canceled after the initial data is returned.

Declaration SW IFT

func observeSingleEvent(of eventType: DataEventType, with block: @escaping (DataSnapshot) -> Void) OBJECTIVE-C

- (void)observeSingleEventOfType:(FIRDataEventType)eventType withBlock: (nonnull void (^)(FIRDataSnapshot *_Nonnull))block;


block





-observeSingleEventOfType:andPreviousSiblingKeyWithBlock: This is equivalent to observeEventType:withBlock:, except the block is immediately canceled after the initial data is returned. In addition, for FIRDataEventTypeChildAdded, FIRDataEventTypeChildMoved, and FIRDataEventTypeChildChanged events, your block will be passed the key of the previous node by priority order.

Declaration SW IFT

func observeSingleEvent(of eventType: DataEventType, andPreviousSiblingKeyWith block: @escaping (DataSnapshot, String?) -> Void) OBJECTIVE-C

- (void)observeSingleEventOfType:(FIRDataEventType)eventType andPreviousSiblingKeyWithBlock: (nonnull void (^)(FIRDataSnapshot *_Nonnull, NSString *_Nullable))block;


block




The block that should be called. It is passed the data as a FIRDataSnapshot and the previous child’s ke

-observeSingleEventOfType:withBlock:withCancelBlock: This is equivalent to observeEventType:withBlock:, except the block is immediately canceled after the initial data is returned. The cancelBlock will be called if you do not have permission to read data at this location.

Declaration SW IFT

func observeSingleEvent(of eventType: DataEventType, with block: @escaping (DataSnapshot) -> Void, withCancel cancelBlock: ((Error) -> Void)? = nil) OBJECTIVE-C

- (void) observeSingleEventOfType:(FIRDataEventType)eventType

withBlock:(nonnull void (^)(FIRDataSnapshot *_Nonnull))block withCancelBlock:(nullable void (^)(NSError *_Nonnull))cancelBlock;


block

cancelBlock






observeSingleEventOfType:andPreviousSiblingKeyWithBlock:withCancelBlock: This is equivalent to observeEventType:withBlock:, except the block is immediately canceled after the initial data is returned. In addition, for FIRDataEventTypeChildAdded, FIRDataEventTypeChildMoved, and FIRDataEventTypeChildChanged events, your block will be passed the key of the previous node by priority order. The cancelBlock will be called if you do not have permission to read data at this location.

Declaration SW IFT

func observeSingleEvent(of eventType: DataEventType, andPreviousSiblingKeyWith block: @escaping (DataSnapshot, String?) -> Void, withCancel cancelBlock: ((Error) -> Void)? = nil) OBJECTIVE-C

- (void)observeSingleEventOfType:(FIRDataEventType)eventType andPreviousSiblingKeyWithBlock:(nonnull void (^)(FIRDataSnapshot *_Nonnull, NSString *_Nullable))block withCancelBlock: (nullable void (^)(NSError *_Nonnull))cancelBlock;



block

The block that should be called. It is passed the data as a FIRDataSnapshot and the previous child’s

cancelBlock


Detaching observers



-removeObserverWithHandle: Detach a block previously attached with observeEventType:withBlock:.

Declaration SW IFT

func removeObserver(withHandle handle: UInt) OBJECTIVE-C

- (void)removeObserverWithHandle:(FIRDatabaseHandle)handle;

Parameters handle



The handle returned by the call to observeEventType:withBlock: which we are trying to remove.

-keepSynced: By calling keepSynced:YES on a location, the data for that location will automatically be downloaded and kept in sync, even when no listeners are attached for that location. Additionally, while a location is kept synced, it will not be evicted from the persistent disk cache.

Declaration SW IFT

func keepSynced(_ keepSynced: Bool)

OBJECTIVE-C

- (void)keepSynced:(BOOL)keepSynced;

Parameters keepSynced



Pass YES to keep this location synchronized, pass NO to stop synchronization.

-removeAllObservers Removes all observers at the current reference, but does not remove any observers at child references. removeAllObservers must be called again for each child reference where a listener was established to remove the observers.

Declaration SW IFT

func removeAllObservers() OBJECTIVE-C

- (void)removeAllObservers;

Querying and limiting



-queryLimitedToFirst: queryLimitedToFirst: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryLimitedToFirst: will respond to at most the first limit child nodes.

Declaration SW IFT

func queryLimited(toFirst limit: UInt) -> DatabaseQuery

OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryLimitedToFirst:(NSUInteger)limit;

Parameters limit





-queryLimitedToLast: queryLimitedToLast: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryLimitedToLast: will respond to at most the last limit child nodes.

Declaration SW IFT

func queryLimited(toLast limit: UInt) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryLimitedToLast:(NSUInteger)limit;

Parameters limit





-queryOrderedByChild:

queryOrderBy: is used to generate a reference to a view of the data that’s been sorted by the values of a particular child key. This method is intended to be used in combination with queryStartingAtValue:, queryEndingAtValue:, or queryEqualToValue:.

Declaration SW IFT

func queryOrdered(byChild key: String) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryOrderedByChild:(nonnull NSString *)key;

Parameters key

The child key to use in ordering data visible to the returned FIRDatabaseQuery

Return Value A FIRDatabaseQuery instance, ordered by the values of the specified child key.



-queryOrderedByKey queryOrderedByKey: is used to generate a reference to a view of the data that’s been sorted by child key. This method is intended to be used in combination with queryStartingAtValue:, queryEndingAtValue:, or queryEqualToValue:.

Declaration SW IFT

func queryOrderedByKey() -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryOrderedByKey;

Return Value A FIRDatabaseQuery instance, ordered by child keys.



-queryOrderedByPriority queryOrderedByPriority: is used to generate a reference to a view of the data that’s been sorted by child priority. This method is intended to be used in combination with queryStartingAtValue:, queryEndingAtValue:, or queryEqualToValue:.

Declaration SW IFT

func queryOrderedByPriority() -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryOrderedByPriority;

Return Value A FIRDatabaseQuery instance, ordered by child priorities.



-queryStartingAtValue: queryStartingAtValue: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryStartingAtValue: will respond to events at nodes with a value greater than or equal to startValue.

Declaration SW IFT

func queryStarting(atValue startValue: Any?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryStartingAtValue:(nullable id)startValue;


Return Value


A FIRDatabaseQuery instance, limited to data with value greater than or equal to startValue



-queryStartingAtValue:childKey: queryStartingAtValue:childKey: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryStartingAtValue:childKey will respond to events at nodes with a value greater than startValue, or equal to startValue and with a key greater than or equal to childKey.

Declaration SW IFT

func queryStarting(atValue startValue: Any?, childKey: String?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryStartingAtValue:(nullable id)startValue childKey: (nullable NSString *)childKey;


childKey


The lower bound, inclusive, for the key of nodes with value equal to startValue




-queryEndingAtValue: queryEndingAtValue: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryEndingAtValue: will respond to events at nodes with a value less than or equal to endValue.

Declaration SW IFT

func queryEnding(atValue endValue: Any?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryEndingAtValue:(nullable id)endValue;

Parameters endValue





-queryEndingAtValue:childKey: queryEndingAtValue:childKey: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryEndingAtValue:childKey will respond to events at nodes with a value less than endValue, or equal to endValue and with a key less than or equal to childKey.

Declaration SW IFT

func queryEnding(atValue endValue: Any?, childKey: String?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryEndingAtValue:(nullable id)endValue childKey:(nullable NSString *)childKey;

Parameters endValue

childKey

Return Value


The upper bound, inclusive, for the key of nodes with value equal to endValue

A FIRDatabaseQuery instance, limited to data with value less than or equal to endValue



-queryEqualToValue: queryEqualToValue: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryEqualToValue: will respond to events at nodes with a value equal to the supplied argument.

Declaration SW IFT

func queryEqual(toValue value: Any?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryEqualToValue:(nullable id)value;

Parameters value


Return Value A FIRDatabaseQuery instance, limited to data with the supplied value.



-queryEqualToValue:childKey: queryEqualToValue:childKey: is used to generate a reference to a limited view of the data at this location. The FIRDatabaseQuery instance returned by queryEqualToValue:childKey will respond to events at nodes with a value equal to the supplied argument with a key equal to childKey. There will be at most one node that matches because child keys are unique.

Declaration SW IFT

func queryEqual(toValue value: Any?, childKey: String?) -> DatabaseQuery OBJECTIVE-C

- (nonnull FIRDatabaseQuery *)queryEqualToValue:(nullable id)value childKey:(nullable NSString *)childKey;

Parameters value

childKey


The key of nodes with the right value

Return Value A FIRDatabaseQuery instance, limited to data with the supplied value and the key.

Managing presence



-onDisconnectSetValue: Ensure the data at this location is set to the specified value when the client is disconnected (due to closing the browser, navigating to a new page, or network issues). onDisconnectSetValue: is especially useful for implementing presence systems, where a value should be changed or cleared when a user disconnects so that he appears offline to other users.

Declaration SW IFT

func onDisconnectSetValue(_ value: Any?) OBJECTIVE-C

- (void)onDisconnectSetValue:(nullable id)value;

Parameters value

The value to be set after the connection is lost.



-onDisconnectSetValue:withCompletionBlock: Ensure the data at this location is set to the specified value when the client is disconnected (due to closing the browser, navigating to a new page, or network issues). The completion block will be triggered when the operation has been successfully queued up on the Firebase Database servers

Declaration SW IFT

func onDisconnectSetValue(_ value: Any?, withCompletionBlock block: @escaping (Error?, DatabaseReference) -> Void) OBJECTIVE-C

- (void)onDisconnectSetValue:(nullable id)value withCompletionBlock: (nonnull void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters value

block




Block to be triggered when the operation has been queued up on the Firebase Database servers

-onDisconnectSetValue:andPriority: Ensure the data at this location is set to the specified value and priority when the client is disconnected (due to closing the browser, navigating to a new page, or network issues).

Declaration SW IFT

func onDisconnectSetValue(_ value: Any?, andPriority priority: Any) OBJECTIVE-C

- (void)onDisconnectSetValue:(nullable id)value andPriority:(nonnull id)priority;

Parameters value

priority




The priority to be set after the connection is lost.

-onDisconnectSetValue:andPriority:withCompletionBlock: Ensure the data at this location is set to the specified value and priority when the client is disconnected (due to closing the browser, navigating to a new page, or network issues). The completion block will be triggered when the operation has been successfully queued up on the Firebase Database servers

Declaration SW IFT

func onDisconnectSetValue(_ value: Any?, andPriority priority: Any?, withCompletionBlock block: @escaping (Error?, DatabaseReference) -> Void) OBJECTIVE-C

- (void)onDisconnectSetValue:(nullable id)value andPriority:(nullable id)priority withCompletionBlock: (nonnull void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters value

priority

block




The priority to be set after the connection is lost.


-onDisconnectRemoveValue Ensure the data at this location is removed when the client is disconnected (due to closing the app, navigating to a new page, or network issues).

onDisconnectRemoveValue is especially useful for implementing presence systems.

Declaration SW IFT

func onDisconnectRemoveValue() OBJECTIVE-C

- (void)onDisconnectRemoveValue;



-onDisconnectRemoveValueWithCompletionBlock: Ensure the data at this location is removed when the client is disconnected (due to closing the app, navigating to a new page, or network issues). onDisconnectRemoveValueWithCompletionBlock: is especially useful for implementing presence systems.

Declaration SW IFT

func onDisconnectRemoveValue(completionBlock block: @escaping (Error?, DatabaseReference) -> Void) OBJECTIVE-C

- (void)onDisconnectRemoveValueWithCompletionBlock: (nonnull void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters block




-onDisconnectUpdateChildValues: Ensure the data has the specified child values updated when the client is disconnected (due to closing the browser, navigating to a new page, or network issues).

Declaration

SWIFT

func onDisconnectUpdateChildValues(_ values: [AnyHashable : Any]) OBJECTIVE-C

- (void)onDisconnectUpdateChildValues:(nonnull NSDictionary *)values;

Parameters values



A dictionary of child node keys and the values to set them to after the connection is lost.

-onDisconnectUpdateChildValues:withCompletionBlock: Ensure the data has the specified child values updated when the client is disconnected (due to closing the browser, navigating to a new page, or network issues).

Declaration SW IFT

func onDisconnectUpdateChildValues(_ values: [AnyHashable : Any], withCompletionBlock block: @escaping (Error?, DatabaseReference) -> Void) OBJECTIVE-C

- (void)onDisconnectUpdateChildValues:(nonnull NSDictionary *)values withCompletionBlock: (nonnull void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters values

block



A dictionary of child node keys and the values to set them to after the connection is lost.

A block that will be called once the operation has been queued up on the Firebase Database servers

-cancelDisconnectOperations Cancel any operations that are set to run on disconnect. If you previously called onDisconnectSetValue:, onDisconnectRemoveValue:, or onDisconnectUpdateChildValues:, and no longer want the values updated when the connection is lost, call cancelDisconnectOperations:

Declaration SW IFT

func cancelDisconnectOperations() OBJECTIVE-C

- (void)cancelDisconnectOperations;



-cancelDisconnectOperationsWithCompletionBlock: Cancel any operations that are set to run on disconnect. If you previously called onDisconnectSetValue:, onDisconnectRemoveValue:, or onDisconnectUpdateChildValues:, and no longer want the values updated when the connection is lost, call cancelDisconnectOperations:

Declaration SW IFT

func cancelDisconnectOperations(completionBlock block: ((Error?, DatabaseReference) -> Void)? = nil) OBJECTIVE-C

- (void)cancelDisconnectOperationsWithCompletionBlock: (nullable void (^)(NSError *_Nullable, FIRDatabaseReference *_Nonnull))block;

Parameters block

A block that will be triggered once the Firebase Database servers have acknowledged the cancel request.

Manual Connection Management



+goOffline Manually disconnect the Firebase Database client from the server and disable automatic reconnection.

The Firebase Database client automatically maintains a persistent connection to the Firebase Database server, which will remain active indefinitely and reconnect when disconnected. However, the goOffline( ) and goOnline( ) methods may be used to manually control the client connection in cases where a persistent connection is undesirable. While offline, the Firebase Database client will no longer receive data updates from the server. However, all database operations performed locally will continue to immediately fire events, allowing your application to continue behaving normally. Additionally, each operation performed locally will automatically be queued and retried upon reconnection to the Firebase Database server. To reconnect to the Firebase Database server and begin receiving remote events, see goOnline( ). Once the connection is reestablished, the Firebase Database client will transmit the appropriate data and fire the appropriate events so that your client catches up automatically. Note: Invoking this method will impact all Firebase Database connections.

Declaration SW IFT

class func goOffline() OBJECTIVE-C

+ (void)goOffline;



+goOnline Manually reestablish a connection to the Firebase Database server and enable automatic reconnection. The Firebase Database client automatically maintains a persistent connection to the Firebase Database server, which will remain active indefinitely and reconnect when disconnected. However, the goOffline( ) and goOnline( ) methods may be used to manually control the client connection in cases where a persistent connection is undesirable. This method should be used after invoking goOffline( ) to disable the active connection. Once reconnected, the Firebase Database client will automatically transmit the proper data and fire the appropriate events so that your client catches up automatically. To disconnect from the Firebase Database server, see goOffline( ). Note: Invoking this method will impact all Firebase Database connections.

Declaration

SWIFT

class func goOnline() OBJECTIVE-C

+ (void)goOnline;

Transactions



-runTransactionBlock: Performs an optimistic-concurrency transactional update to the data at this location. Your block will be called with a FIRMutableData instance that contains the current data at this location. Your block should update this data to the value you wish to write to this location, and then return an instance of FIRTransactionResult with the new data. If, when the operation reaches the server, it turns out that this client had stale data, your block will be run again with the latest data from the server. When your block is run, you may decide to abort the transaction by returning [FIRTransactionResult abort].

Declaration SW IFT

func runTransactionBlock(_ block: @escaping (MutableData) -> TransactionResult) OBJECTIVE-C

- (void)runTransactionBlock: (nonnull FIRTransactionResult *_Nonnull (^)(FIRMutableData *_Nonnull))block;

Parameters block



This block receives the current data at this location and must return an instance of FIRTransactionResult

-runTransactionBlock:andCompletionBlock:

Performs an optimistic-concurrency transactional update to the data at this location. Your block will be called with a FIRMutableData instance that contains the current data at this location. Your block should update this data to the value you wish to write to this location, and then return an instance of FIRTransactionResult with the new data. If, when the operation reaches the server, it turns out that this client had stale data, your block will be run again with the latest data from the server. When your block is run, you may decide to abort the transaction by returning [FIRTransactionResult abort].

Declaration SW IFT

func runTransactionBlock(_ block: @escaping (MutableData) -> TransactionResult, andCompletionBlock completionBlock: @escaping (Error?, Bool, DataSnapshot?) -> Void) OBJECTIVE-C

- (void)runTransactionBlock:(nonnull FIRTransactionResult *_Nonnull (^)( FIRMutableData *_Nonnull))block andCompletionBlock: (nonnull void (^)(NSError *_Nullable, BOOL, FIRDataSnapshot *_Nullable))completionBlock;

Parameters block

completionBlock



This block receives the current data at this location and must return an instance of FIRTransactio

This block will be triggered once the transaction is complete, whether it was successful or not. It w indicate if there was an error, whether or not the data was committed, and what the current value data at this location is.

-runTransactionBlock:andCompletionBlock:withLocalEvents: Performs an optimistic-concurrency transactional update to the data at this location. Your block will be called with a FIRMutableData instance that contains the current data at this location. Your block should update this data to the value you wish to write to this location, and then return an instance of FIRTransactionResult with the new data. If, when the operation reaches the server, it turns out that this client had stale data, your block will be run again with the latest data from the server.

When your block is run, you may decide to abort the transaction by return [FIRTransactionResult abort]. Since your block may be run multiple times, this client could see several immediate states that don’t exist on the server. You can suppress those immediate states until the server confirms the final state of the transaction.

Declaration SW IFT

func runTransactionBlock(_ block: @escaping (MutableData) -> TransactionResult, andCompletionBlock completionBlock: ((Error?, Bool, DataSnapshot?) -> Void)?, withLocalEvents localEvents: Bool) OBJECTIVE-C

- (void)runTransactionBlock:(nonnull FIRTransactionResult *_Nonnull (^)( FIRMutableData *_Nonnull))block andCompletionBlock: (nullable void (^)(NSError *_Nullable, BOOL, FIRDataSnapshot *_Nullable))completionBlock withLocalEvents:(BOOL)localEvents;

Parameters block

completionBlock

localEvents

This block receives the current data at this location and must return an instance of FIRTransactio

This block will be triggered once the transaction is complete, whether it was successful or not. It w indicate if there was an error, whether or not the data was committed, and what the current value data at this location is.

Set this to NO to suppress events raised for intermediate states, and only get events based on th state of the transaction.

Retrieving String Representation



-description Gets the absolute URL of this Firebase Database location.

Declaration SW IFT

func description() -> String OBJECTIVE-C

- (nonnull NSString *)description;

Return Value The absolute URL of the referenced Firebase Database location.

Properties



parent Gets a FIRDatabaseReference for the parent location. If this instance refers to the root of your Firebase Database, it has no parent, and therefore parent( ) will return null.

Declaration SW IFT

var parent: DatabaseReference? { get } OBJECTIVE-C

@property (readonly, strong, nonatomic, nullable) FIRDatabaseReference *parent;

Return Value A FIRDatabaseReference for the parent location.



root Gets a FIRDatabaseReference for the root location

Declaration SW IFT

var root: DatabaseReference { get } OBJECTIVE-C

@property (readonly, strong, nonatomic) FIRDatabaseReference *_Nonnull root;

Return Value A new FIRDatabaseReference to root location.



key Gets the last token in a Firebase Database location (e.g. ‘fred’ in https://SampleChat.firebaseIOdemo.com/users/fred)

Declaration SW IFT

var key: String { get } OBJECTIVE-C

@property (readonly, strong, nonatomic) NSString *_Nonnull key;

Return Value The key of the location this reference points to.



URL Gets the URL for the Firebase Database location referenced by this FIRDatabaseReference.

Declaration SW IFT

var url: String { get } OBJECTIVE-C

@property (readonly, strong, nonatomic) NSString *_Nonnull URL;

Return Value The url of the location this reference points to.



database Gets the FIRDatabase instance associated with this reference.

Declaration SW IFT

var database: Database { get } OBJECTIVE-C

@property (readonly, strong, nonatomic) FIRDatabase *_Nonnull database;

Return Value The FIRDatabase object for this reference.

Firebase In IOS Programming

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