Observable的interval可以产生一个计时器，并且这个计时器不熟Runloop影响，那它究竟是何方神圣呢，下面通过源码解析下它的实现
interval的使用
let timer:Observable<Int> = Observable<Int>.interval(1, scheduler: MainScheduler.instance)
timer.subscribe(onNext: { (timer) in
print("hahaha")
}).disposed(by: disposeBag)
源码解析
interval注册源码分析
//Timer.swift
extension ObservableType where E : RxAbstractInteger {
...
public static func interval(_ period: RxTimeInterval, scheduler: SchedulerType)
-> Observable<E> {
return Timer(
dueTime: period,
period: period,
scheduler: scheduler
)
}
}
final private class Timer<E: RxAbstractInteger>: Producer<E> {
...
override func run<O: ObserverType>(_ observer: O, cancel: Cancelable) -> (sink: Disposable, subscription: Disposable) where O.E == E {
if self._period != nil {
let sink = TimerSink(parent: self, observer: observer, cancel: cancel)
let subscription = sink.run()
return (sink: sink, subscription: subscription)
}
else {
let sink = TimerOneOffSink(parent: self, observer: observer, cancel: cancel)
let subscription = sink.run()
return (sink: sink, subscription: subscription)
}
}
}
//Producer.swift
class Producer<Element> : Observable<Element> {
override init() {
super.init()
}
override func subscribe<O : ObserverType>(_ observer: O) -> Disposable where O.E == Element {
if !CurrentThreadScheduler.isScheduleRequired {
// The returned disposable needs to release all references once it was disposed.
let disposer = SinkDisposer()
let sinkAndSubscription = self.run(observer, cancel: disposer)
disposer.setSinkAndSubscription(sink: sinkAndSubscription.sink, subscription: sinkAndSubscription.subscription)
return disposer
}
else {
return CurrentThreadScheduler.instance.schedule(()) { _ in
let disposer = SinkDisposer()
let sinkAndSubscription = self.run(observer, cancel: disposer)
disposer.setSinkAndSubscription(sink: sinkAndSubscription.sink, subscription: sinkAndSubscription.subscription)
return disposer
}
}
}
func run<O : ObserverType>(_ observer: O, cancel: Cancelable) -> (sink: Disposable, subscription: Disposable) where O.E == Element {
rxAbstractMethod()
}
}
在执行interval时，会创建内部类Timer，这个类实现了run方法，它的父类Producer实现了subscribe方法
subscribe监听源码分析
//ObservableType+Extensions.swift
extension ObservableType {
public func subscribe(_ on: @escaping (Event<E>) -> Void)
-> Disposable {
let observer = AnonymousObserver { e in
on(e)
}
return self.asObservable().subscribe(observer)
}
func subscribe(onNext: ((E) -> Void)? = nil, onError: ((Swift.Error) -> Void)? = nil, onCompleted: (() -> Void)? = nil, onDisposed: (() -> Void)? = nil)
-> Disposable {
...
let observer = AnonymousObserver<E> { event in
#if DEBUG
synchronizationTracker.register(synchronizationErrorMessage: .default)
defer { synchronizationTracker.unregister() }
#endif
switch event {
case .next(let value):
onNext?(value)
case .error(let error):
if let onError = onError {..
onError(error)
}
else {
Hooks.defaultErrorHandler(callStack, error)
}
disposable.dispose()
case .completed:
onCompleted?()
disposable.dispose()
}
}
return Disposables.create(
self.asObservable().subscribe(observer),
disposable
)
}
}
这个地方会调用Timer的父类Producer的subscribe方法，然后父类的subscribe方法会调用Timer的run方法，run中会创建一个TimerSink对象，并会执行它的run方法
//Timer.swift
final private class TimerSink<O: ObserverType> : Sink<O> where O.E : RxAbstractInteger {
typealias Parent = Timer<O.E>
private let _parent: Parent
private let _lock = RecursiveLock()
init(parent: Parent, observer: O, cancel: Cancelable) {
self._parent = parent
super.init(observer: observer, cancel: cancel)
}
func run() -> Disposable {
return self._parent._scheduler.schedulePeriodic(0 as O.E, startAfter: self._parent._dueTime, period: self._parent._period!) { state in
self._lock.lock(); defer { self._lock.unlock() }
self.forwardOn(.next(state))
return state &+ 1
}
}
}
TimerSink对象的run方法
//DispatchQueueConfiguration.swift
extension DispatchQueueConfiguration {
func schedulePeriodic<StateType>(_ state: StateType, startAfter: TimeInterval, period: TimeInterval, action: @escaping (StateType) -> StateType) -> Disposable {
let initial = DispatchTime.now() + dispatchInterval(startAfter)
var timerState = state
let timer = DispatchSource.makeTimerSource(queue: self.queue)
timer.schedule(deadline: initial, repeating: dispatchInterval(period), leeway: self.leeway)
// TODO:
// This looks horrible, and yes, it is.
// It looks like Apple has made a conceputal change here, and I'm unsure why.
// Need more info on this.
// It looks like just setting timer to fire and not holding a reference to it
// until deadline causes timer cancellation.
var timerReference: DispatchSourceTimer? = timer
let cancelTimer = Disposables.create {
timerReference?.cancel()
timerReference = nil
}
timer.setEventHandler(handler: {
if cancelTimer.isDisposed {
return
}
timerState = action(timerState)
})
timer.resume()
return cancelTimer
}
}
到这里，我们可以看到这个计时器的庐山真面目了，原来他就是DispatchSource！这个计时器会调用action方法，而action就是TimerSink，run方法传入的尾随闭包，这个闭包会执行forwardOn方法，这个方法的实现在TimerSink的父类Sink中
//Sink.swift
class Sink<O : ObserverType> : Disposable {
...
init(observer: O, cancel: Cancelable) {
#if TRACE_RESOURCES
_ = Resources.incrementTotal()
#endif
self._observer = observer
self._cancel = cancel
}
final func forwardOn(_ event: Event<O.E>) {
#if DEBUG
self._synchronizationTracker.register(synchronizationErrorMessage: .default)
defer { self._synchronizationTracker.unregister() }
#endif
if isFlagSet(self._disposed, 1) {
return
}
self._observer.on(event)
}
...
deinit {
#if TRACE_RESOURCES
_ = Resources.decrementTotal()
#endif
}
}
forwardOn会调用observer的on方法，即调用AnonymousObserver的父类的ObserverBase的on方法
//ObserverBase.swift
class ObserverBase<ElementType> : Disposable, ObserverType {
typealias E = ElementType
private let _isStopped = AtomicInt(0)
func on(_ event: Event<E>) {
switch event {
case .next:
if load(self._isStopped) == 0 {
self.onCore(event)
}
case .error, .completed:
if fetchOr(self._isStopped, 1) == 0 {
self.onCore(event)
}
}
}
func onCore(_ event: Event<E>) {
rxAbstractMethod()
}
func dispose() {
fetchOr(self._isStopped, 1)
}
}
onCore即调用AnonymousObserver的onCore方法
//AnonymousObserver.swift
final class AnonymousObserver<ElementType> : ObserverBase<ElementType> {
...
override func onCore(_ event: Event<Element>) {
return self._eventHandler(event)
}
...
}
最终执行eventHandle，并传入event-onNext，进行事件处理
到此我们的源码就以及分析完成了，下面是我的思维导图
intervel
生活如此美好，今天就点到为止。。。
