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FirebaseDatabase Framework Reference

DataSnapshot

class DataSnapshot : NSObject

A DataSnapshot contains data from a Firebase Database location. Any time you read Firebase data, you receive the data as a DataSnapshot.

DataSnapshots are passed to the blocks you attach with observe(_:with:) or observeSingleEvent(of:with:). They are efficiently-generated immutable copies of the data at a Firebase Database location. They can’t be modified and will never change. To modify data at a location, use a DatabaseReference (e.g. with setValue(_:)).

  • Gets a DataSnapshot 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’). If the child location has no data, an empty DataSnapshot is returned.

    Declaration

    Swift

    func childSnapshot(forPath childPathString: String) -> DataSnapshot

    Parameters

    childPathString

    A relative path to the location of child data.

    Return Value

    The DataSnapshot for the child location.

  • Return true if the specified child exists.

    Declaration

    Swift

    func hasChild(_ childPathString: String) -> Bool

    Parameters

    childPathString

    A relative path to the location of a potential child.

    Return Value

    true if data exists at the specified childPathString, else false.

  • Return true if the DataSnapshot has any children.

    Declaration

    Swift

    func hasChildren() -> Bool

    Return Value

    true if this snapshot has any children, else false.

  • Return true if the DataSnapshot contains a non-null value.

    Declaration

    Swift

    func exists() -> Bool

    Return Value

    true if this snapshot contains a non-null value, else false.

Data export

  • Returns the raw value at this location, coupled with any metadata, such as priority.

    Priorities, where they exist, are accessible under the “.priority” key in instances of NSDictionary. For leaf locations with priorities, the value will be under the “.value” key.

    Declaration

    Swift

    func valueInExportFormat() -> Any?

Properties

  • Returns the contents of this data snapshot as native types.

    Data types returned:

    • Dictionary
    • Array
    • NSNumber-bridgeable types, including Bool

    • String

    Declaration

    Swift

    var value: Any? { get }

    Return Value

    The data as a native object.

  • Gets the number of children for this DataSnapshot.

    Declaration

    Swift

    var childrenCount: UInt { get }

    Return Value

    An integer indicating the number of children.

  • ref

    Gets a DatabaseReference for the location that this data came from.

    Declaration

    Swift

    var ref: FIRDatabaseReference { get }

    Return Value

    A DatabaseReference instance for the location of this data.

  • key

    The key of the location that generated this DataSnapshot.

    Declaration

    Swift

    var key: String { get }

    Return Value

    A String containing the key for the location of this DataSnapshot.

  • An iterator for snapshots of the child nodes in this snapshot.

     for var child in snapshot.children {
   // ...
 }

    Declaration

    Swift

    var children: NSEnumerator { get }

    Return Value

    An NSEnumerator of the children.

  • The priority of the data in this DataSnapshot.

    Declaration

    Swift

    var priority: Any? { get }

    Return Value

    The priority as a String, or nil if no priority was set.

  • Retrieves the value of a snapshot and converts it to an instance of caller-specified type. Throws DecodingError.valueNotFound if the document does not exist and T is not an Optional.

    See Database.Decoder for more details about the decoding process.

    Declaration

    Swift

    func data<T: Decodable>(as type: T.Type,
                        decoder: Database.Decoder =
                          Database.Decoder()) throws -> T