1.響應式編程

響應式編程(Reactive Programming，簡稱RP)， 也是一種編程范式悬槽，于1997年提出，可以簡化異步編程瞬浓，提供更優(yōu)雅的數(shù)據(jù)綁定初婆， 一般與函數(shù)式融合在一起，所以也會叫做:函數(shù)響應式編程(Functional Reactive Programming猿棉，簡稱FRP)

• 比較著名的磅叛、成熟的響應式框架：

  • ReactiveCocoa

    • 簡稱RAC，有Objective-C铺根、Swift版本
    • 官網(wǎng): http://reactivecocoa.io/
    • github:https://github.com/ReactiveCocoa

  • ReactiveX
    簡稱Rx宪躯，有眾多編程語言的版本，比如RxJava位迂、RxKotlin访雪、RxJS、RxCpp掂林、RxPHP臣缀、RxGo、RxSwift等等

    • 官網(wǎng): http://reactivex.io/
    • github: https://github.com/ReactiveX

2.RxSwift

• RxSwift(ReactiveX for Swift)泻帮，ReactiveX的Swift版本

  • 源碼:https://github.com/ReactiveX/RxSwift
  • 中文文檔: https://beeth0ven.github.io/RxSwift-Chinese-Documentation/

• 模塊說明

  • RxSwift:Rx標準API的Swift實現(xiàn)精置，不包括任何iOS相關的內(nèi)容

  • RxCocoa:基于RxSwift，給iOS UI控件擴展了很多Rx特性

    
    
    image.png

• RxSwift的核心角色

  • Observable:負責發(fā)送事件(Event)

  • Observer:負責訂閱Observable锣杂，監(jiān)聽Observable發(fā)送的事件(Event)

    
    
    image.png

• Event有3種

  • next:攜帶具體數(shù)據(jù)
  • error:攜帶錯誤信息脂倦，表明Observable終止，不會再發(fā)出事件
  • completed:表明Observable終止元莫，不會再發(fā)出事件

2.1 創(chuàng)建赖阻、訂閱Observable1

/*
var observable = Observable<Int>.create { observer in
    observer.onNext(1)
    observer.onCompleted()
    return Disposables.create()
}
// 等價于
observable = Observable.just(1)
observable = Observable.of(1)
observable = Observable.from([1])

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

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

observable.subscribe(onNext: {
    print("next", $0)
}, onError: {
    print("error", $0)
}, onCompleted: {
    print("completed")
}, onDisposed: {
    print("dispose")
}).dispose()

2.2 創(chuàng)建、訂閱Observable2

/// 定時器
let observable = Observable<Int>.timer(.seconds(3),
                                       period: .seconds(1),
                                       scheduler: MainScheduler.instance)

observable.map {
        "數(shù)值是\($0)"
        }.bind(to: label.rx.text)
        .disposed(by: bag)
 
 /// range
 //        Observable.range(start: 2, count: 10)
 //            .subscribe { (event : Event<Int>) in
 //            print(event)
 //        }.dispose()
         
 /// repeatElement
 //        Observable.repeatElement("hello")
 //        .take(4)
 //            .subscribe { (event) in
 //                print(event)
 //        }.dispose()

2.3 創(chuàng)建Observer

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()

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()

2.4 擴展Binder屬性

extension Reactive where Base: UIView {
    var hidden: Binder<Bool> {
        Binder<Bool>(base) { view, value in
            view.isHidden = value
        }
    }
}
let observable = Observable<Int>.interval(.seconds(1),
                                          scheduler: MainScheduler.instance)

observable.map { $0 % 2 == 0 }
    .bind(to: button.rx.hidden)
    .disposed(by: bag)

2.5 傳統(tǒng)的狀態(tài)監(jiān)聽

在開發(fā)中經(jīng)常要對各種狀態(tài)進行監(jiān)聽踱蠢，傳統(tǒng)的常見監(jiān)聽方案有

• KVO
• Target-Action
• Notification
• Delegate
• Block Callback
  傳統(tǒng)方案經(jīng)常會出現(xiàn)錯綜復雜的依賴關系火欧、耦合性較高，還需要編寫重復的非業(yè)務代碼

2.6 RxSwift的狀態(tài)監(jiān)聽1

button.rx.tap
 .subscribe(onNext: {
        print("按鈕被點擊了1")
    })
 .disposed(by: bag)

let data = Observable.just(
    [Person(name: "Jack", age: 10),
     Person(name: "Rose", age: 20)]
)

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)

tableView.rx.modelSelected(Person.self)
    .subscribe(onNext: { person in
        print("點擊了", person.name)
    }).disposed(by: bag)

2.7 RxSwift的狀態(tài)監(jiān)聽2

class Dog: NSObject {
    @objc dynamic var name: String?
}
dog.rx.observe(String.self, "name")
    .subscribe(onNext: { name in
        print("name is", name ?? "nil")
    }).disposed(by: bag)
dog.name = "larry"
dog.name = "wangwang"

NotificationCenter.default.rx.notification(UIApplication.didEnterBackgroundNotification) .subscribe(onNext: { notification in
    print("APP進入后臺", notification)
}).disposed(by: bag)

2.8 既是Observable，又是Observer

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

slider.rx.value.map {
    "當前數(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)

// 諸如UISlider.rx.value苇侵、UTextField.rx.text這類屬性值赶盔，既是Observable，又是Observer
// 它們是RxCocoa.ControlProperty類型

2.9 Disposable

• 每當Observable被訂閱時榆浓，都會返回一個Disposable實例于未，當調(diào)用Disposable的dispose，就相當于取消訂閱
• 在不需要再接收事件時哀军，建議取消訂閱沉眶，釋放資源。有3種常見方式取消訂閱
• 立即取消訂閱(一次性訂閱)

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

// 當bag銷毀(deinit)時杉适，會自動調(diào)用Disposable實例的dispose
observable.subscribe { event in
    print(event)
}.disposed(by: bag)

// self銷毀時(deinit)時谎倔，會自動調(diào)用Disposable實例的dispose
let _ = observable.takeUntil(self.rx.deallocated).subscribe { event in
    print(event)
}

2.10 PublishSubject、ReplaySubject猿推、BehaviorSubject片习、Variable

/// 四種序列

///1. PublishSubject, 訂閱者只能接受，訂閱之后發(fā)出的事件
//let publishSub = PublishSubject<String>()
 
//不會接收到
//publishSub.onNext("coderwhy")
//publishSub.subscribe { (event : Event<String>) in
//    print(event)
//}.disposed(by: bag)
 
//會接收到
//publishSub.onNext("coderwhy")

///2蹬叭、ReplaySubject, 訂閱者可以接受訂閱之前的事件&訂閱之后的事件
 
//let replaySub = ReplaySubject<String>.create(bufferSize: 4)
//replaySub.onNext("a")
//replaySub.onNext("b")
//replaySub.onNext("c")
//replaySub.onNext("d")
//replaySub.onNext("e")
//
//replaySub.subscribe { (event) in
//    print(event)
//}.disposed(by: bag)
//replaySub.onNext("f")

//3藕咏、BehaviorSubject, 訂閱者可以接受，訂閱之前的最后一個事件
 
//let behaviorSub = BehaviorSubject(value: "a")
//behaviorSub.onNext("b")
//behaviorSub.onNext("c")
//behaviorSub.onNext("d")
//
//behaviorSub.subscribe { (event : Event<String>) in
//    print(event)
//}.disposed(by: bag)
//
//behaviorSub.onNext("e")
//behaviorSub.onNext("f")
//behaviorSub.onNext("g")

///4秽五、Variable,
///1孽查、相當于對BehaviorSubject進行裝箱
///2、如果想將Variable當成Observable坦喘，讓訂閱者進行訂閱時盲再，需要asObservable轉(zhuǎn)成Observable
///3、如果Variable打算發(fā)出事件瓣铣，直接修改對象的value即可
///4答朋、當事件結(jié)束時，Variable會自動發(fā)出completed事件

//let variable = Variable("a")
//variable.value = "1"
//variable.asObservable().subscribe { (event : Event<String>) in
//    print(event)
//}.disposed(by: bag)
//variable.value = "2"

 //: map flatMap使用

///    map
 Observable.of(1,2,3,4).map { (value) -> Int in
     return value * value
 }
 .subscribe { (event : Event<Int>) in
     print(event)
 }
 .disposed(by: bag)

/// flatMap使用
 
 struct Student {
     var score : Variable<Double>
 }
 
 let stu1 = Student(score: Variable(80))
 let stu2 = Student(score: Variable(100))
 
 let studentVariable = Variable(stu1)
 studentVariable.asObservable()
     .flatMapLatest({ (stu : Student) -> Observable<Double> in
         return stu.score.asObservable()
     })
//   .flatMap { (stu : Student) -> Observable<Double> in
//       return stu.score.asObservable()
//   }
     .subscribe { (event : Event<Double>) in
         print(event.element as Any)
     }.disposed(by: bag)
 
 studentVariable.value = stu2
 stu1.score.value = 1999
 */