1、背景

    響應(yīng)式編程（Reactive Programming仙辟，簡(jiǎn)稱RP）也是一種編程范式同波，于1997年提出，可以簡(jiǎn)化異步編程叠国，提供更優(yōu)雅的數(shù)據(jù)綁定
  一般與函數(shù)式融合在一起未檩，所以也會(huì)叫做：函數(shù)響應(yīng)式編程（Functional Reactive Programming，簡(jiǎn)稱FRP）

比較著名的煎饼、成熟的響應(yīng)式框架  
  ReactiveCocoa
  簡(jiǎn)稱RAC讹挎，有Objective-C、Swift版本
  官網(wǎng)： http://reactivecocoa.io/
  github：https://github.com/ReactiveCocoa

  ReactiveX(推薦)
  簡(jiǎn)稱Rx吆玖，有眾多編程語言的版本筒溃，比如RxJava、RxKotlin沾乘、RxJS怜奖、RxCpp、RxPHP翅阵、RxGo歪玲、RxSwift等等
  官網(wǎng)： http://reactivex.io/
  github： https://github.com/ReactiveX

2、RxSwift安裝

RxSwift（ReactiveX for Swift）掷匠，ReactiveX的Swift版本
  源碼：https://github.com/ReactiveX/RxSwift
  中文文檔： https://beeth0ven.github.io/RxSwift-Chinese-Documentation/

RxSwift的github上已經(jīng)有詳細(xì)的安裝教程滥崩，這里只演示CocoaPods方式的安裝
  Podfile
    use_frameworks!

    target 'target_name' do 
      pod 'RxSwift', '~> 5' 
      pod 'RxCocoa', '~> 5' 
    end

  命令行
    pod repo update
    pod install

  導(dǎo)入模塊
    import RxSwift 
    import RxCocoa

模塊說明
  RxSwift：Rx標(biāo)準(zhǔn)API的Swift實(shí)現(xiàn)，不包括任何iOS相關(guān)的內(nèi)容
  RxCocoa：基于RxSwift讹语，給iOS UI控件擴(kuò)展了很多Rx特性

3钙皮、RxSwift的核心角色

Observable：負(fù)責(zé)發(fā)送事件（Event）
Observer：負(fù)責(zé)訂閱Observable，監(jiān)聽Observable發(fā)送的事件（Event）

Event有3種
  next：攜帶具體數(shù)據(jù)
  error：攜帶錯(cuò)誤信息顽决，表明Observable終止短条，不會(huì)再發(fā)出事件
  completed：表明Observable終止，不會(huì)再發(fā)出事件

  public enum Event<Element> {
    /// Next element is produced. 
    case next(Element)

    /// Sequence terminated with an error. 
    case error(Swift.Error)

    /// Sequence completed successfully. 
    case completed
  }

4才菠、Disposable

每當(dāng)Observable被訂閱時(shí)茸时，都會(huì)返回一個(gè)Disposable實(shí)例，當(dāng)調(diào)用Disposable的dispose赋访，就相當(dāng)于取消訂閱
    在不需要再接收事件時(shí)可都，建議取消訂閱缓待，釋放資源。有3種常見方式取消訂閱
      1. 立即取消訂閱（一次性訂閱）
        observable.subscribe { event in 
          print(event) 
        }.dispose()
      2. 當(dāng)bag銷毀（deinit）時(shí)汹粤，會(huì)自動(dòng)調(diào)用Disposable實(shí)例的dispose
        observable.subscribe { event in 
          print(event) 
        }.disposed(by: bag)
      3. self銷毀時(shí)（deinit）時(shí)命斧，會(huì)自動(dòng)調(diào)用Disposable實(shí)例的dispose
        let _ = observable.take(until: self.rx.deallocated).subscribe { event in
          print(event) 
        }

5、創(chuàng)建嘱兼、訂閱Observable

/// 1.普通創(chuàng)建
var observable = Observable<Int>.create { observer in 
  observer.onNext(1) 
  observer.onCompleted() 
  return Disposables.create() 
} 
// 等價(jià)于 
observable = Observable.just(1) //只能發(fā)送單個(gè)數(shù)據(jù)
observable = Observable.of(1) //可發(fā)送多個(gè)數(shù)據(jù)
observable = Observable.from([1])//可發(fā)送多個(gè)數(shù)據(jù)

var observable = Observable<Int>.create { observer in 
  observer.onNext(1) 
  observer.onNext(2) 
  observer.onNext(3) 
  observer.onCompleted() 
  return Disposables.create() 
} 
// 等價(jià)于 
observable = Observable.of(1, 2, 3) 
observable = Observable.from([1, 2, 3])

observable.subscribe { event in 
  print(event) 
}.dispose()

observable.subscribe(onNext: { 
  print("next", $0) 
}, onError: {
  print("error", $0) 
}, onCompleted: {
  print("completed") 
}, onDisposed: {
  print("dispose") 
}).dispose()
//等價(jià)于
let bag = DisposeBag()
observable.subscribe { event in
    switch event {
    case .next(let element):
        print("next", element)
    case .error(let error):
        print("error",error)
    case .completed:
        print("completed")
    }
}.disposed(by: bag)

/// 2.間隔時(shí)間發(fā)送, 比如: 兩秒之后, 每隔一秒鐘在主線程發(fā)送一次
let observable = Observable<Int>.timer(.seconds(2), period: .seconds(1), scheduler: MainScheduler.instance)
//bind(to: 也是訂閱, 傳入?yún)?shù)為observer
let _ = observable
    .take(until: self.rx.deallocated)
    .map {"\($0)"}
    .bind(to: UILabel().rx.text)//rx.text 是一個(gè)observer

6国葬、 創(chuàng)建Observer

//方式一: 通過AnyObserver
let observer = AnyObserver<Int>.init{ event in
    switch event {
    case .next(let data):
        print(data)
    case .completed:
        print("completed")
    case .error(let error):
        print("error", error)
    }
}
Observable.just(1).subscribe(observer).dispose()

//方式二: 通過Binder
let binder = Binder<String>(label){ label, text in
    label.text = text
}
Observable.just(1).map{"數(shù)值是\($0)"}.subscribe(binder).dispose()
Observable.just(1).map{"數(shù)值是\($0)"}.bind(to: binder).dispose()

7、擴(kuò)展Binder屬性

/// 需求: 從兩秒后開始, 按鈕每隔1秒進(jìn)行一次顯隱切換
//方法一:
let observable = Observable<Int>.timer(.seconds(2), period: .seconds(1), scheduler: MainScheduler.instance)
let binder = Binder<Bool>(button){ button, value in
    button.isHidden = value
}
observable.map{ $0 % 2 == 0 }.bind(to: binder).disposed(by: bag)

//方法二:
let observable = Observable<Int>.timer(.seconds(2), period: .seconds(1), scheduler: MainScheduler.instance)
observable.map{ $0 % 2 == 0 }.bind(to: button.rx.hidden).disposed(by: bag) //要實(shí)現(xiàn)button.rx.hidden, 需要給button擴(kuò)展屬性

//擴(kuò)展Binder屬性:  來實(shí)現(xiàn)button.rx.hidden
extension Reactive where Base: UIView{
    var hidden: Binder<Bool>{//只讀計(jì)算屬性
        Binder<Bool>(base) { view, value in
            view.isHidden = value
        }
    }
}

8芹壕、RxSwift的狀態(tài)監(jiān)聽

/// ①監(jiān)聽按鈕點(diǎn)擊狀態(tài)
button.rx.tap.subscribe(onNext: { 
  print("按鈕被點(diǎn)擊了1") 
}).disposed(by: bag)

/// ②監(jiān)聽列表狀態(tài)
let data = Observable.just([ 
  Person(name: "Jack", age: 10), 
  Person(name: "Rose", age: 20) 
]) 
// 1.將數(shù)據(jù)綁定到TableView上
data.bind(to: tableView.rx.items(cellIdentifier: "cell")) { row, person, cell in
  cell.textLabel?.text = person.name
  cell.detailTextLabel?.text = "\(person.age)" 
}.disposed(by: bag)
// 2.TableViewCell點(diǎn)擊事件響應(yīng)
tableView.rx.modelSelected(Person.self) 
  .subscribe(onNext: { person in 
    print("點(diǎn)擊了", person.name) 
  }).disposed(by: bag)

/// ③監(jiān)聽對(duì)象屬性變化(類似KVO)
class Dog: NSObject { 
  //@objc dynamic應(yīng)用于變量是為了讓變量能夠使用kvo機(jī)制
  @objc dynamic var name: String? 
} 

let dog = Dog()
let bag = DisposeBag()
dog.rx.observe(String.self, "name")
  .subscribe(onNext: { name in
    print("name is", name ?? "nil")
  }).disposed(by: bag)
dog.name = "Kris"
dog.name = "Amok"


/// ④監(jiān)聽通知
NotificationCenter.default.rx
      .notification(UIApplication.didEnterBackgroundNotification) 
      .subscribe(onNext: { notification in 
        print("APP進(jìn)入后臺(tái)", notification) 
      }).disposed(by: bag)

9汇四、既是Observable，又是Observer

Observable.just(0.8).bind(to: slider.rx.value).dispose()

slider.rx.value.map { 
  "當(dāng)前數(shù)值是：\($0)" 
}.bind(to: textField.rx.text).disposed(by: bag)

textField.rx.text
  .subscribe(onNext: { text in 
    print("text is", text ?? "nil") 
  }).disposed(by: bag)

// 總結(jié): 諸如UISlider.rx.value踢涌、UTextField.rx.text這類屬性值通孽，既是Observable，又是Observer
//  它們是RxCocoa.ControlProperty類型