RxSwift的核心逻辑很重要，是分析整个框架的基础。
希望通俗易通，没有弄思维导图，个人觉得太多对象和线条的思维导图，还没看就眼花。不多说直接奔主题，以Observable开始，重点是核心逻辑，其他细节先忽略。例子：
let observable = Observable.create { (anyObserver) -> Disposable in
anyObserver.onNext("发送响应")
anyObserver.onCompleted()
return Disposables.create()
}
observable.subscribe { (text) in
print("收到响应")
}.disposed(by: disposbag)
- 首先是创建序列:
let observable = Observable.create { (observer) -> Disposable in
...
}
- 开始进入源码，
Observable继承了ObservableType协议（协议方法需要在别的扩展里找到）：
public class Observable : ObservableType {
...
}
ObservableType实现了create，返回AnonymousObservable（保存了序列闭包subscribeHandler）：
extension ObservableType {
public static func create(_ subscribe: @escaping (AnyObserver) -> Disposable) -> Observable {
return AnonymousObservable(subscribe)//内部保存了闭包subscribe
}
}
final private class AnonymousObservable: Producer {
...
init(_ subscribeHandler: @escaping SubscribeHandler) {
self._subscribeHandler = subscribeHandler
}
}
- 然后回到外面进行订阅，也就是
AnonymousObservable.subscribe：
observable.subscribe { (event) in
...
}
-
AnonymousObservable没有具体的subscribe方法，这时候找父类，然而这里面是层层套，最后能看到它实现了ObservableType协议：
final private class AnonymousObservable: Producer {
...
}
class Producer : Observable {
...
}
public class Observable : ObservableType {
...
}
具体协议方法里，创建了匿名内部观察者AnonymousObserver（保存了事件闭包eventHandler），返回销毁者：
extension ObservableType {
...
public func subscribe(onNext: ((E) -> Void)? = nil, onError: ((Swift.Error) -> Void)? = nil, onCompleted: (() -> Void)? = nil, onDisposed: (() -> Void)? = nil)
-> Disposable {
...
let observer = AnonymousObserver { event in
...
}
return Disposables.create(
self.asObservable().subscribe(observer),
disposable
)
}
...
}
final class AnonymousObserver : ObserverBase {
...
init(_ eventHandler: @escaping EventHandler) {
...
self._eventHandler = eventHandler
}
...
}
- 在返回销毁者时调用
self.asObservable().subscribe，首先是self.asObservable()
public class Observable : ObservableType {
public func subscribe(_ observer: O) -> Disposable where O.E == E {
rxAbstractMethod() //具体方法由子类实现
}
public func asObservable() -> Observable {
return self //子类可能会实现具体方法，最后结果都是返回一个序列Observable
}
}
然后self.asObservable().subscribe =>
self.subscribe =>
AnonymousObservable.subscribe =>
Producer.subscribe
class Producer : Observable {
...
override func subscribe(_ 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
}
}
}
...
}
-
Producer最终会调用self.run,而子类AnonymousObservable实现了具体的run方法：
final private class AnonymousObservable: Producer {
...
override init(observer: O, cancel: Cancelable) {
super.init(observer: observer, cancel: cancel)
}
override func run(_ observer: O, cancel: Cancelable) -> (sink: Disposable, subscription: Disposable) where O.E == Element {
let sink = AnonymousObservableSink(observer: observer, cancel: cancel)
let subscription = sink.run(self)
return (sink: sink, subscription: subscription)
}
}
- 然后
AnonymousObservable的run里面创建了AnonymousObservableSink(业务下沉)，保存了这里的observer(即AnonymousObserver)和cancel，AnonymousObservableSink拥有所有的功能——观察，发送，响应，销毁，相当于manager的作用，然后调用sink.run
final private class AnonymousObservableSink: Sink, ObserverType {
...
override init(observer: O, cancel: Cancelable) {
super.init(observer: observer, cancel: cancel)
}
...
}
class Sink : Disposable {
...
init(observer: O, cancel: Cancelable) {
...
self._observer = observer
self._cancel = cancel
}
...
}
-
sink.run内部的parent便是传进来的AnonymousObservable，然后创建AnyObserver（保存AnonymousObservableSink.on函数），并利用AnonymousObservable保存的序列闭包subscribeHandler发送到外面：
final private class AnonymousObservableSink: Sink, ObserverType {
...
func run(_ parent: Parent) -> Disposable {
return parent._subscribeHandler(AnyObserver(self))
}
}
public struct AnyObserver : ObserverType {
...
public init(_ observer: O) where O.E == Element {
self.observer = observer.on
}
...
}
- 外面的
_subscribeHandler就会调用anyObserver.onNext("")，而anyObserver就是AnyObserver：
let observable = Observable.create { (anyObserver) -> Disposable in
anyObserver.onNext("发送信号")
anyObserver.onCompleted() //发送完成
return Disposables.create() //销毁者
}
-
AnyObserver继承了ObserverType协议：
public struct AnyObserver : ObserverType {
...
}
extension ObserverType {
public func onNext(_ element: E) {
self.on(.next(element))
}
...
}
-
AnyObserver又具体实现了self.on：
public struct AnyObserver : ObserverType {
...
public func on(_ event: Event) {
return self.observer(event)
}
...
}
- 然后调用
self.observer，便是AnyObserver保存的AnonymousObservableSink.on：
inal private class AnonymousObservableSink: Sink, ObserverType {
...
func on(_ event: Event) {
...
switch event {
case .next:
if load(self._isStopped) == 1 {
return
}
self.forwardOn(event)
case .error, .completed:
if fetchOr(self._isStopped, 1) == 0 {
self.forwardOn(event)
self.dispose()
}
}
}
...
}
- 然后根据
event进入.next，调用self.forwardOn，AnonymousObservableSink没有具体的forwardOn，找父类Sink：
class Sink : Disposable {
...
final func forwardOn(_ event: Event) {
...
if isFlagSet(self._disposed, 1) {
return
}
self._observer.on(event)
}
...
}
-
self._observer便是AnonymousObservableSink保存的AnonymousObserver，AnonymousObserver没有具体的on方法，找父类ObserverBase：
final class AnonymousObserver : ObserverBase {
...
}
class ObserverBase : Disposable, ObserverType {
...
func on(_ event: Event) {
switch event {
case .next:
if load(self._isStopped) == 0 {
self.onCore(event)
}
case .error, .completed:
if fetchOr(self._isStopped, 1) == 0 {
self.onCore(event)
}
}
}
...
}
- 然后又回到
AnonymousObserver.onCore：
final class AnonymousObserver : ObserverBase {
...
override func onCore(_ event: Event) {
return self._eventHandler(event)
}
...
}
-
self._eventHandler便是AnonymousObserver保存的事件闭包eventHandler：
extension ObservableType {
...
public func subscribe(onNext: ((E) -> Void)? = nil, onError: ((Swift.Error) -> Void)? = nil, onCompleted: (() -> Void)? = nil, onDisposed: (() -> Void)? = nil)
-> Disposable {
...
let observer = AnonymousObserver { event in
...
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
)
}
...
}
- 最后根据
event调用外面传进来的onNext?(value)，便回到最初外面的响应闭包：
observable.subscribe { (text) in
print("收到响应")
}.disposed(by: disposbag)
这样才能基本完成一个订阅响应的流程，还是不懂的可以自己断点慢慢走一遍。