SingleAssignmentDisposable
特点是只能设置一次disposable
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public final class SingleAssignmentDisposable : DisposeBase, Cancelable {
private enum DisposeState: Int32 {
case disposed = 1
case disposableSet = 2
}
// state
private let _state = AtomicInt(0)
private var _disposable = nil as Disposable?
/// - returns: A value that indicates whether the object is disposed.
public var isDisposed: Bool {
return isFlagSet(self._state, DisposeState.disposed.rawValue)
}
/// Initializes a new instance of the `SingleAssignmentDisposable`.
public override init() {
super.init()
}
/// Gets or sets the underlying disposable. After disposal, the result of getting this property is undefined.
///
/// **Throws exception if the `SingleAssignmentDisposable` has already been assigned to.**
public func setDisposable(_ disposable: Disposable) {
self._disposable = disposable
let previousState = fetchOr(self._state, DisposeState.disposableSet.rawValue)
// 这个逻辑实现，只能设置一次disposable
if (previousState & DisposeState.disposableSet.rawValue) != 0 {
rxFatalError("oldState.disposable != nil")
}
if (previousState & DisposeState.disposed.rawValue) != 0 {
disposable.dispose()
self._disposable = nil
}
}
/// Disposes the underlying disposable.
public func dispose() {
let previousState = fetchOr(self._state, DisposeState.disposed.rawValue)
if (previousState & DisposeState.disposed.rawValue) != 0 {
return
}
if (previousState & DisposeState.disposableSet.rawValue) != 0 {
guard let disposable = self._disposable else {
rxFatalError("Disposable not set")
}
disposable.dispose()
self._disposable = nil
}
}
}
Disposable见另一篇
注：文中源码来自RxSwift