Instance Methodswift 6.0.3Synchronization

    storeIfNil(_:)

    Atomically initializes this reference if its current value is nil, then returns the initialized value. If this reference is already initialized, then storeIfNil(_:) discards its supplied argument and returns the current value without updating it.

    iOS
    18.0+
    macOS
    15.0+
    tvOS
    18.0+
    visionOS
    2.0+
    watchOS
    11.0+
    func storeIfNil(_ desired: consuming Instance) -> Instance
    Mangled symbol
    s15Synchronization19AtomicLazyReferenceV10storeIfNilyxxnF What are these?
    FNV24 hash
    J9FT

    Parameters

    desired

    A value of Instance that we will attempt to store if the lazy reference is currently nil.

    Returns

    The value of Instance that was successfully stored within the lazy reference. This may or may not be the same value of Instance that was passed to this function.

    The following example demonstrates how this can be used to implement a thread-safe lazily initialized reference:

    class Image {
  let _histogram = AtomicLazyReference<Histogram>()

  // This is safe to call concurrently from multiple threads.
  var atomicLazyHistogram: Histogram {
    if let histogram = _histogram.load() { return histogram }
    // Note that code here may run concurrently on
    // multiple threads, but only one of them will get to
    // succeed setting the reference.
    let histogram = ...
    return _histogram.storeIfNil(histogram)
  }
}