PublishSubject
Represents an object that is both an observable sequence as well as an observer.
Each notification is broadcasted to all subscribed observers.
- 线程安全
- 作为observable重写了subscribe方法，订阅时不会收到事件
- 作为observer, 在事件处理函数
on中把事件发送给所有订阅者 - 订阅之后返回的key, 可以用于取消订阅
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public final class PublishSubject<Element>
: Observable<Element>
, SubjectType
, Cancelable
, ObserverType
, SynchronizedUnsubscribeType {
public typealias SubjectObserverType = PublishSubject<Element>
typealias Observers = AnyObserver<Element>.s
typealias DisposeKey = Observers.KeyType
/// Indicates whether the subject has any observers
public var hasObservers: Bool {
self._lock.lock()
let count = self._observers.count > 0
self._lock.unlock()
return count
}
private let _lock = RecursiveLock()
// state
private var _isDisposed = false
private var _observers = Observers()
private var _stopped = false
private var _stoppedEvent = nil as Event<Element>?
#if DEBUG
private let _synchronizationTracker = SynchronizationTracker()
#endif
/// Indicates whether the subject has been isDisposed.
public var isDisposed: Bool {
return self._isDisposed
}
/// Creates a subject.
public override init() {
super.init()
#if TRACE_RESOURCES
_ = Resources.incrementTotal()
#endif
}
/// Notifies all subscribed observers about next event.
///
/// - parameter event: Event to send to the observers.
public func on(_ event: Event<Element>) {
#if DEBUG
self._synchronizationTracker.register(synchronizationErrorMessage: .default)
defer { self._synchronizationTracker.unregister() }
#endif
dispatch(self._synchronized_on(event), event)
}
func _synchronized_on(_ event: Event<Element>) -> Observers {
self._lock.lock(); defer { self._lock.unlock() }
switch event {
case .next:
if self._isDisposed || self._stopped {
return Observers()
}
return self._observers
case .completed, .error:
if self._stoppedEvent == nil {
self._stoppedEvent = event
self._stopped = true
let observers = self._observers
self._observers.removeAll()
return observers
}
return Observers()
}
}
/**
Subscribes an observer to the subject.
- parameter observer: Observer to subscribe to the subject.
- returns: Disposable object that can be used to unsubscribe the observer from the subject.
*/
public override func subscribe<Observer: ObserverType>(_ observer: Observer) -> Disposable where Observer.Element == Element {
self._lock.lock()
let subscription = self._synchronized_subscribe(observer)
self._lock.unlock()
return subscription
}
func _synchronized_subscribe<Observer: ObserverType>(_ observer: Observer) -> Disposable where Observer.Element == Element {
if let stoppedEvent = self._stoppedEvent {
observer.on(stoppedEvent)
return Disposables.create()
}
if self._isDisposed {
observer.on(.error(RxError.disposed(object: self)))
return Disposables.create()
}
let key = self._observers.insert(observer.on)
return SubscriptionDisposable(owner: self, key: key)
}
func synchronizedUnsubscribe(_ disposeKey: DisposeKey) {
self._lock.lock()
self._synchronized_unsubscribe(disposeKey)
self._lock.unlock()
}
func _synchronized_unsubscribe(_ disposeKey: DisposeKey) {
_ = self._observers.removeKey(disposeKey)
}
/// Returns observer interface for subject.
public func asObserver() -> PublishSubject<Element> {
return self
}
/// Unsubscribe all observers and release resources.
public func dispose() {
self._lock.lock()
self._synchronized_dispose()
self._lock.unlock()
}
final func _synchronized_dispose() {
self._isDisposed = true
self._observers.removeAll()
self._stoppedEvent = nil
}
#if TRACE_RESOURCES
deinit {
_ = Resources.decrementTotal()
}
#endif
}
References
注：文中源码来自RxSwift