1.响应式编程
响应式编程(Reactive Programming，简称RP)， 也是一种编程范式，于1997年提出，可以简化异步编程，提供更优雅的数据绑定， 一般与函数式融合在一起，所以也会叫做:函数响应式编程(Functional Reactive Programming，简称FRP)
- 比较著名的、成熟的响应式框架：
-
ReactiveCocoa
- 简称RAC，有Objective-C、Swift版本
- 官网: http://reactivecocoa.io/
- github:https://github.com/ReactiveCocoa
-
ReactiveX
简称Rx，有众多编程语言的版本，比如RxJava、RxKotlin、RxJS、RxCpp、RxPHP、RxGo、RxSwift等等- 官网: http://reactivex.io/
- github: https://github.com/ReactiveX
-
2.RxSwift
-
RxSwift(ReactiveX for Swift)，ReactiveX的Swift版本
-
模块说明
- RxSwift:Rx标准API的Swift实现，不包括任何iOS相关的内容
-
RxCocoa:基于RxSwift，给iOS UI控件扩展了很多Rx特性
image.png
-
RxSwift的核心角色
- Observable:负责发送事件(Event)
-
Observer:负责订阅Observable，监听Observable发送的事件(Event)
image.png
-
Event有3种
- next:携带具体数据
- error:携带错误信息，表明Observable终止，不会再发出事件
- completed:表明Observable终止，不会再发出事件
2.1 创建、订阅Observable1
/*
var observable = Observable<Int>.create { observer in
observer.onNext(1)
observer.onCompleted()
return Disposables.create()
}
// 等价于
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()
}
// 等价于
observable = Observable.of(1, 2, 3)
observable = Observable.from([1, 2, 3])
/// 订阅
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 创建、订阅Observable2
/// 定时器
let observable = Observable<Int>.timer(.seconds(3),
period: .seconds(1),
scheduler: MainScheduler.instance)
observable.map {
"数值是\($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 创建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 { "数值是\($0)" }.subscribe(binder).dispose()
Observable.just(1).map { "数值是\($0)" }.bind(to: binder).dispose()
2.4 扩展Binder属性
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 传统的状态监听
在开发中经常要对各种状态进行监听，传统的常见监听方案有
- KVO
- Target-Action
- Notification
- Delegate
- Block Callback
传统方案经常会出现错综复杂的依赖关系、耦合性较高，还需要编写重复的非业务代码
2.6 RxSwift的状态监听1
button.rx.tap
.subscribe(onNext: {
print("按钮被点击了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("点击了", person.name)
}).disposed(by: bag)
2.7 RxSwift的状态监听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进入后台", 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 {
"当前数值是:\($0)"
}.bind(to: textField.rx.text)
.disposed(by: bag)
textField.rx.text
.subscribe(onNext: { text in
print("text is", text ?? "nil")
}).disposed(by: bag)
// 诸如UISlider.rx.value、UTextField.rx.text这类属性值，既是Observable，又是Observer
// 它们是RxCocoa.ControlProperty类型
2.9 Disposable
- 每当Observable被订阅时，都会返回一个Disposable实例，当调用Disposable的dispose，就相当于取消订阅
- 在不需要再接收事件时，建议取消订阅，释放资源。有3种常见方式取消订阅
- 立即取消订阅(一次性订阅)
observable.subscribe { event in
print(event)
}.dispose()
// 当bag销毁(deinit)时，会自动调用Disposable实例的dispose
observable.subscribe { event in
print(event)
}.disposed(by: bag)
// self销毁时(deinit)时，会自动调用Disposable实例的dispose
let _ = observable.takeUntil(self.rx.deallocated).subscribe { event in
print(event)
}
2.10 PublishSubject、ReplaySubject、BehaviorSubject、Variable
/// 四种序列
///1. PublishSubject, 订阅者只能接受，订阅之后发出的事件
//let publishSub = PublishSubject<String>()
//不会接收到
//publishSub.onNext("coderwhy")
//publishSub.subscribe { (event : Event<String>) in
// print(event)
//}.disposed(by: bag)
//会接收到
//publishSub.onNext("coderwhy")
///2、ReplaySubject, 订阅者可以接受订阅之前的事件&订阅之后的事件
//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、BehaviorSubject, 订阅者可以接受，订阅之前的最后一个事件
//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、Variable,
///1、相当于对BehaviorSubject进行装箱
///2、如果想将Variable当成Observable，让订阅者进行订阅时，需要asObservable转成Observable
///3、如果Variable打算发出事件，直接修改对象的value即可
///4、当事件结束时，Variable会自动发出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
*/
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