函數(shù)式編程

• 響應(yīng)式編程(Reactive Programming,簡(jiǎn)稱(chēng) RP)
• 也是一種范式編程
• 一般與函數(shù)式融合一起,所以也叫函數(shù)響應(yīng)式編程(Functiona Reactive Programming,簡(jiǎn)稱(chēng) FRP)

ReactiveX

• 有很多種編程語(yǔ)言,如RxJava RxSwift...
• 安裝

  # Podfile
  use_frameworks!
  
  target 'YOUR_TARGET_NAME' do
      pod 'RxSwift', '~> 5'
      pod 'RxCocoa', '~> 5'
  end
  
  # RxTest and RxBlocking make the most sense in the context of unit/integration tests
  target 'YOUR_TESTING_TARGET' do
      pod 'RxBlocking', '~> 5'
      pod 'RxTest', '~> 5'
  end
  

RxSwift 核心角色

• Observable: 負(fù)責(zé)發(fā)送實(shí)踐的 (Event)

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

  public enum Event<Element> {
      
      case next(Element) ` 攜帶數(shù)據(jù) `
      
      case error(Swift.Error)  `遵守 swift error 協(xié)議,后面消息不發(fā)送`
      
      case completed  ` 觀(guān)察者終止行動(dòng) `
  }
  
  

Observable 發(fā)布消息

• 代碼

  let obs = Observable<Int>.create{ observer in
  
      observer.onNext(11)
      observer.onNext(22)
      observer.onNext(33)
      observer.onCompleted() `完成監(jiān)聽(tīng)`
      return Disposables.create()
  }
  

subscribe 監(jiān)聽(tīng)消息

• 代碼

  import RxCocoa
  import RxSwift
  
  let bag = DisposeBag() // 回收袋
  
  //第一種方法
      obs.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)
      }
      
      
  // 第二種方法
  
      obs.subscribe(onNext: { (element) in
              print("next", element)
          }, onError: { (error) in
              print("error", error)
          }, onCompleted: {
              print("completed")
          })        
          
      
      // 定時(shí)器功能
      let obs = Observable<Int>.timer(.seconds(3), period: .seconds(5), scheduler: MainScheduler.instance)
      // 3 秒后啟動(dòng)定時(shí)器,每間隔 5 秒,在 主線(xiàn)程上發(fā)一次消息
      
  

Disposable 釋放 obs

• 每當(dāng) Observable 被訂閱時(shí),都會(huì)返回一個(gè) Disposable 實(shí)例,當(dāng)調(diào)用 Disposable 的 dispose , 就相當(dāng)于取消訂閱

• 在不需要再接收事件時(shí),建議取消訂閱,釋放資源,常見(jiàn)有三種取消訂閱方式

  // 第一種
  obs.subscribe { event in
        // do something  
  }.dispose()  //立即取消訂閱
  
  
  // 第二種, 
  obs.subscribe { event in
        // do something  
  }.dispose(by: bag)  //bag 回收袋,controller 銷(xiāo)毀, bag 銷(xiāo)毀,obs 調(diào)用取消訂閱接口
  
  
  //第三種
  obs
  .takeUntil(self.rx.deallocated) //直到 控制器調(diào)用 deallocated 方法,取消訂閱
  .subscribe { event in
      // do something
  }
  

創(chuàng)建 Observer

• 通過(guò) AnyObserver 類(lèi)型創(chuàng)建 obs

      let obs = AnyObserver<Int>.init { event in
          switch event {
              case .next(let element):
                  print("next", element)
              case .error(let error):
                  print("error", error)
              case .completed:
                  print("completed")
          }
      }
          
      // 只調(diào)用一次,發(fā)送消息內(nèi)容為 5
      Observable.just(5).subscribe(obs).dispose()           
  
  

• 通過(guò) Observable 類(lèi)型創(chuàng)建 obs

      let obs = Observable<Int>.create{ observer in
          observer.onNext(33)
          observer.onCompleted()
          return Disposables.create()
      }        
          
      //監(jiān)聽(tīng)
      obs.subscribe(onNext: { (element) in
              print("next", element)
          }, onError: { (error) in
              print("error", error)
          }, onCompleted: {
              print("completed")
      }).disposed(by: bag)    
          
      obs.subscribe { event in
          switch event {
              case .next(let element):
                  print("next", element)
              case .error(let error):
                  print("error", error)
              case .completed:
                  print("completed")
          }
      }.dispose()    
      
  

• 通過(guò) bind 創(chuàng)建

      
      let binder = Binder<String>(label) { label, text in
          label.text = text
      }
       
      // 監(jiān)聽(tīng)
      Observable.just(1).map{ "數(shù)值: \($0)" }.subscribe(binder).dispose()
      Observable.just(1).map{ "數(shù)值: \($0)" }.bind(to:binder).dispose()
      
  

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