atomic properties in swift.

AtomicPropertyContainers.swift

fileprivate final class ReadWriteLock {
    private var rwlock: pthread_rwlock_t = {
        var rwlock = pthread_rwlock_t()
        pthread_rwlock_init(&rwlock, nil)
        return rwlock
    }()

    func writeLock() {
        pthread_rwlock_wrlock(&(self.rwlock))
    }

    func readLock() {
        pthread_rwlock_rdlock(&(self.rwlock))
    }

    func unlock() {
        pthread_rwlock_unlock(&(self.rwlock))
    }
}

final class AtomicPropertyContainer<T> {
    typealias DidSetBlock = (_: T)->Void

    private var internalValue: T
    private let lock = ReadWriteLock()
    private let didSetBlock: DidSetBlock?

    init(_ initialValue: T, didSetBlock: DidSetBlock? = nil) {
        self.internalValue = initialValue
        self.didSetBlock = didSetBlock
    }

    var value: T {
        get {
            self.lock.readLock()
            let value = self.internalValue
            self.lock.unlock()
            return value
        }
        set {
            self.lock.writeLock()
            self.internalValue = newValue
            self.lock.unlock()
            if let block = self.didSetBlock {
                DispatchQueue.global(qos: .default) .async {
                    block(newValue)
                }
            }
        }
    }
}

final class AtomicWrappedPropertyContainer<T> {
    typealias DidSetBlock = (_: T?)->Void

    private var internalValue: T?
    private let lock = ReadWriteLock()
    private let didSetBlock: DidSetBlock?

    init(_ initialValue: T? = nil, didSetBlock: DidSetBlock? = nil) {
        self.internalValue = initialValue
        self.didSetBlock = didSetBlock
    }

    var value: T? {
        get {
            self.lock.readLock()
            let currentValue = self.internalValue
            self.lock.unlock()
            return currentValue
        }
        set {
            self.lock.writeLock()
            self.internalValue = newValue
            self.lock.unlock()
            if let block = self.didSetBlock {
                DispatchQueue.global(qos: .default) .async {
                    block(newValue)
                }
            }
        }
    }
}