ReadWriteCoordinator

public final class ReadWriteCoordinator

ReadWriteCoordinator instances can be used to coordinate access to a mutable resource shared across multiple threads.

You can think of the ReadWriteCoordinator as a read/write lock having the following properties:

  • The read lock allows any number of readers to execute concurrently.

  • The write lock allows one and only one writer to execute at a time.

  • As long as there is at least one reader executing, the write lock cannot be acquired.

  • As long as the write lock is held, no readers can execute.

  • Initializes a new ReadWriteCoordinator instance.

    Declaration

    Swift

    public init()

  • Initializes a new ReadWriteCoordinator instance.

    Declaration

    Swift

    public init(queueLabel label: String)

    Parameters

    label

    The value to assign as the label for the Grand Central Dispatch queue that will be created for the new ReadWriteCoordinator.

  • Executes the given function with a read lock held, returning its result.

    Declaration

    Swift

    public func read<R>(_ fn: () -> R)
        -> R

    Parameters

    fn

    A function to perform while a read lock is held.

    Return Value

    The result of calling fn().

  • Enqueues an asynchronous request for the write lock and returns to the caller immediately. When the write lock is eventually acquired, the passed-in function will be executed.

    This provides additional efficiency for callers that do not immediately depend on the results of the operation being performed.

    Declaration

    Swift

    public func enqueueWrite(_ fn: @escaping () -> Void)

    Parameters

    fn

    A function to perform while the write lock is held.

  • Attempts to acquire the write lock, blocking if necessary. Once the write lock has been acquired, the passed-in function will be executed.

    Unlike with enqueueWrite(), this function will block the calling thread if necessary while waiting to acquire the write lock. This function should only be used in cases where the results of the write operation need to be available to the caller immediately upon return of this function.

    Declaration

    Swift

    public func blockingWrite<R>(_ fn: () -> R)
        -> R

    Parameters

    fn

    A function to perform while the write lock is held.

    Return Value

    The result of calling fn().