一、前提：函数响应式编程思想
简单来说 函数响应式编程 = 函数式编程 + 响应式编程
（1）函数式
函数式编程是种编程方式，它将电脑运算视为函数的计算。函数编程语言最重要的基础是λ演算（lambda calculus），而且λ演算的函数可以接受函数当作输入（参数）和输出（返回值）。
y = f(x)
x: 参数 f: 函数 y: 返回值
//把 x 作为一个函数传入 --> x = f(x) 例如 x 值是2，2 = 1+1 = 0 + 2
y = f(f(x))//增加了灵活性
let array = [1,2,3,4,5,6,7]
//筛选数组(1.获取 > 3的数字；2. 获取到的数字 + 1；3. 获取偶数； 4.)
//正常操作--可读性底，清晰度差
for num in array{
if num > 3{
let number = num + 1
if (number % 2 == 0){
print(number)
}
}
}
//RxSwift函数式
array.filter{ $0 > 3}//拿到第一个数大于3
.filter{($0 + 1) % 2 == 0}// +1 获取偶数
.forEach{ print($0)}//输出
//如果需求变化，函数式则直接注释某项filter,完全不影响，正常操作中则需要大改动
（2）响应式
对象对某一数据流变化做出响应的这种编码方式
//对象A和对象B，A和B有一种“说不清”的关系，A要时刻监控B的行为，对B的变化也做出相应的变化。
例如，A是10岁 ，B比A大10岁，20年后，A是30岁， B则是40岁 。---->类似于KVO
二、RxSwift 简单使用
创建序列 -> 订阅序列 -> 发送信号 -> 信号接收
（1）Button点击事件
//修改事件类型 button.rx.controlEvent(.touchUpOutside)
button.rx.tap.subscribe(onNext: { () in
print("被点击了")
//处理事件 ……
}).disposed(by: disposeBag)
（2）手势点击事件
let tap = UITapGestureRecognizer.init()
self.view.addGestureRecognizer(tap)
tap.rx.event.subscribe(onNext: { (tap) in
print(tap.view as Any)
//处理事件
}).disposed(by: disposeBag)
（3）输入框监听
//监听输入变化
textfield.rx.text.orEmpty.changed.subscribe(onNext: { (text) in
print(text)
//处理事件 ……
}).disposed(by: disposeBag)
//绑定，数据传递
textfield.rx.text.bind(to: label.rx.text)
（4）KVO事件监听
self.person.rx.observeWeakly(String.self, "name").subscribe(onNext: { (value) in
print(value as Any)
//处理事件 ……
}).disposed(by: disposeBag)
（5）滑动事件监听
scrollview.rx.contentOffset.subscribe(onNext: { [weak self](content) in
let y = content.y
print(content.y)
//处理事件 ……
}).disposed(by: disposeBag)
（6）定时器
let timer = Observable
.interval(1, scheduler: MainScheduler.instance)
timer.subscribe(onNext: { (time) in
print(time)
//处理事件 ……
}).disposed(by: disposeBag)
（7）通知事件
NotificationCenter.default.rx
.notification(UIResponder.keyboardWillShowNotification)
.subscribe(onNext: { (notification) in
//获取值
let during = notification.userInfo?["UIKeyboardAnimationDurationUserInfoKey"] as? Float
print(during!)
//处理事件 ……
}).disposed(by: disposeBag)
（8）网络请求
let url = URL.init(string: "https://www.baidu.com")
URLSession.shared.dataTask(with: url!) { (data, response, error) in
print("network")
print(String.init(data: data!, encoding: .utf8))
}.resume()
URLSession.shared.rx.response(request: URLRequest.init(url: url!))
.subscribe(onNext: { (data) in
print(data)
}, onError: { (error) in
print(error)
}, onCompleted: {
print("请求完成")
}).disposed(by: disposeBag)
三、RxSwift核心逻辑
（1）逻辑流程：创建序列 -->订阅序列-->发送信号-->接受信号
//1、创建序列
let ob = Observable.create { (obserber) -> Disposable in
// 3:发送信号
obserber.onNext("发送信号")
obserber.onCompleted()
// obserber.onError(NSError.init(domain: "coocieeror", code: 10087, userInfo: nil))
return Disposables.create()
}
//2、订阅序列
let _ = ob.subscribe(onNext: { (text) in//5、返回销毁者(_)
//4、接受信号
print("订阅到:\(text)")
}, onError: { (error) in
//4、接受信号
print("error: \(error)")
}, onCompleted: {
//4、接受信号
print("完成")
}) {
print("销毁")
}
（2）源码分析
1.创建序列之Create
Create源码
//创建返回一个匿名内部类--->AnonymousObservable
public static func create(_ subscribe: @escaping (AnyObserver) -> Disposable) -> Observable {
return AnonymousObservable(subscribe)
}
AnonymousObservable内部类源码
//继承Producer，初始化并保存了一个_subscribeHandler的回调记录
final private class AnonymousObservable: Producer {
// 闭包
typealias SubscribeHandler = (AnyObserver) -> Disposable
let _subscribeHandler: SubscribeHandler
init(_ subscribeHandler: @escaping SubscribeHandler) {
self._subscribeHandler = subscribeHandler//保存闭包-->函数式编程思想
}
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)
}
}
通过源码分析Observable
^创建一个内部类（AnonymousObservable -->继承Producer）
^保存闭包（_subscribeHandler回调）
2.订阅序列之subscribe(onNext
subscribe(onNext源码
/**
创建一个观察者-->AnonymousObserver-->把所有event事件保存到observer里面
返回一个销毁者-->Disposables
*/
public func subscribe(onNext: ((E) -> Void)? = nil, onError: ((Swift.Error) -> Void)? = nil, onCompleted: (() -> Void)? = nil, onDisposed: (() -> Void)? = nil)
-> Disposable {
let disposable: Disposable
if let disposed = onDisposed {
disposable = Disposables.create(with: disposed)
}
else {
disposable = Disposables.create()
}
#if DEBUG
let synchronizationTracker = SynchronizationTracker()
#endif
let callStack = Hooks.recordCallStackOnError ? Hooks.customCaptureSubscriptionCallstack() : []
//创建AnonymousObserver观察者，并且把所有event事件保存到observer里面
let observer = AnonymousObserver { event in
#if DEBUG
synchronizationTracker.register(synchronizationErrorMessage: .default)
defer { synchronizationTracker.unregister() }
#endif
switch event {//判断当前event
case .next(let value)://调用event.next信息，则会调用onNext()
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(//创建一个销毁者返回给subscribe
// self.asObservable()---> 就是创建序列的ob ，subscribe --->调用父类Producer的subscribe
self.asObservable().subscribe(observer),
disposable
)
}
AnonymousObserver观察者源码
/**
保存回调事件闭包（_eventHandler -->所有onNext事件&onError事件&onCompleted事件）
*/
final class AnonymousObserver : ObserverBase {
typealias Element = ElementType
typealias EventHandler = (Event) -> Void
private let _eventHandler : EventHandler
init(_ eventHandler: @escaping EventHandler) {
#if TRACE_RESOURCES
_ = Resources.incrementTotal()
#endif
self._eventHandler = eventHandler
}
override func onCore(_ event: Event) {
return self._eventHandler(event)
}
#if TRACE_RESOURCES
deinit {
_ = Resources.decrementTotal()
}
#endif
}
//进入Producer中的subscribe方法
class Producer : Observable {
override init() {
super.init()
}
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)//调用AnonymousObservable的run方法
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(_ observer: O, cancel: Cancelable) -> (sink: Disposable, subscription: Disposable) where O.E == Element {
rxAbstractMethod()
}
}
//进入AnonymousObservable中的run方法
final private class AnonymousObservable: Producer {
typealias SubscribeHandler = (AnyObserver) -> Disposable
let _subscribeHandler: SubscribeHandler
init(_ subscribeHandler: @escaping SubscribeHandler) {
self._subscribeHandler = subscribeHandler
}
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)//调用了AnonymousObservableSink中的run方法
return (sink: sink, subscription: subscription)
}
}
//进入AnonymousObservableSink中调用run方法
final private class AnonymousObservableSink: Sink, ObserverType {
typealias E = O.E
typealias Parent = AnonymousObservable
// state
private let _isStopped = AtomicInt(0)
#if DEBUG
fileprivate let _synchronizationTracker = SynchronizationTracker()
#endif
override init(observer: O, cancel: Cancelable) {
super.init(observer: observer, cancel: cancel)
}
func on(_ event: Event) {
#if DEBUG
self._synchronizationTracker.register(synchronizationErrorMessage: .default)
defer { self._synchronizationTracker.unregister() }
#endif
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()
}
}
}
func run(_ parent: Parent) -> Disposable {
return parent._subscribeHandler(AnyObserver(self))//run 方法中的_subscribeHandler，是不是很熟悉，是不是在《创建序列》创建的_subscribeHandler 闭包， 调用了_subscribeHandler，传入了AnyObserver(self)-->observer
}
}
是不是有点蒙，来来来， 咱们总结下:
1.创建一个观察者
-->AnonymousObserver（let observer = AnonymousObserver
-->把所有event事件保存到observer里面
2.返回一个销毁者
-->Disposables (return Disposables.create)
-->self.asObservable().subscribe(observer), self.asObservable==创建序列的ob ，subscribe --->调用父类Producer的subscribe
-->进入父类Producer的subscribe方法调用self.run(observer, cancel: disposer)
-->进入AnonymousObservable中的run方法调用sink.run(self)
-->进入AnonymousObservableSink中调用run方法,return parent._subscribeHandler(AnyObserver(self))
-->调用了中保存的闭包回调_subscribeHandler，传入了AnyObserver(self),也就是传入了这个行代码创建的observer
-->直到这个时候， let ob = Observable
-->当obserber调用了，onNext()、onError()、onCompleted()，则通过_eventHandler闭包回调到中的onNext、onError、onCompleted
3.销毁
下面引用下别人的总结流程图
细细品一品
再结合这张图品一品