observable的生命周期
这是一个简短的回顾：
- observable发射包含元素的next事件。它能持续的发送直到：
- 发射error事件被终止或
- 发射completed事件被终止。
- 一旦observable被终止，它将不再发送事件。
创建observables
just
just创建的sequence只能发出一种特定的事件，能正常结束.
of
of是创建一个sequence能发出很多种事件信号
from
from就是从集合中创建sequence，例如数组，字典或者Set
example(of: "just, of, from") {
// 1
let one = 1
let two = 2
let three = 3
// 2
let observable: Observable<Int> = Observable<Int>.just(one)
let observable2 = Observable.of(one, two, three)
let observable3 = Observable.of([one, two, three])
let observable4 = Observable.from([one, two, three])
}
订阅observables
subscribe
订阅sequence发出的事件，比如next事件，error事件等
example(of: "subscribe") {
let one = 1
let two = 2
let three = 3
let observable = Observable.of(one, two, three)
observable.subscribe(onNext: { (element) in
print(element)
})
}
--- Example of: subscribe ---
1
2
3
empty
创建一个空的sequence,只能发出一个completed事件
example(of: "empty") {
let observable = Observable<Void>.empty()
observable.subscribe(onNext: { (element) in
print(element)
}, onCompleted: {
print("Completed")
})
}
--- Example of: empty ---
Completed
never
never就是创建一个sequence，但是不发出任何事件信号
example(of: "never") {
let observable = Observable<Any>.never()
let disposeBag = DisposeBag()
observable
.do(onSubscribe: {
print("Subscribed")
})
.subscribe(onNext: { (element) in
print(element)
}, onCompleted: {
print("Completed")
}, onDisposed: {
print("Disposed")
})
.addDisposableTo(disposeBag)
}
--- Example of: never ---
Subscribed
Disposed
range
range就是创建一个sequence，他会发出这个范围中的从开始到结束的所有事件
example(of: "range") {
// 1
let observable = Observable<Int>.range(start: 1, count: 10)
observable
.subscribe(onNext: { i in
// 2
let n = Double(i)
let fibonacci = Int(((pow(1.61803, n) - pow(0.61803, n)) /
2.23606).rounded())
print(fibonacci)
})
}
--- Example of: range ---
0
1
2
3
5
8
13
21
34
55
Disposing and terminating
dispose
用来手动取消订阅
example(of: "dispose") {
// 1
let observable = Observable.of("A", "B", "C")
// 2
let subscription = observable.subscribe { event in
// 3
print(event)
}
subscription.dispose()
}
--- Example of: dispose ---
next(A)
next(B)
next(C)
completed
DisposeBag
其实就相当于iOS中的ARC，会在适当的时候销毁观察者，相当于内存管理者吧。
example(of: "DisposeBag") {
// 1
let disposeBag = DisposeBag()
// 2
Observable.of("A", "B", "C")
.subscribe { // 3
print($0)
}
.addDisposableTo(disposeBag) // 4
}
--- Example of: DisposeBag ---
next(A)
next(B)
next(C)
completed
create
可以自定义可观察的sequence
example(of: "create") {
enum MyError: Error {
case anError
}
let disposeBag = DisposeBag()
Observable<String>.create { observer in
// 1
observer.onNext("1")
// observer.onError(MyError.anError)
// 2
observer.onCompleted()
// 3
observer.onNext("?")
// 4
return Disposables.create()
}.subscribe(
onNext: { print($0) },
onError: { print($0) },
onCompleted: { print("Completed") },
onDisposed: { print("Disposed") }
)
.addDisposableTo(disposeBag)
}
--- Example of: create ---
1
Completed
Disposed
创建observable工厂
deferred
会为每一为订阅者observer创建一个新的可观察序列
example(of: "deferred") {
let disposeBag = DisposeBag()
// 1
var flip = false
// 2
let factory: Observable<Int> = Observable.deferred {
// 3
flip = !flip
// 4
if flip {
return Observable.of(1, 2, 3)
} else {
return Observable.of(4, 5, 6)
}
}
for _ in 0...3 {
factory.subscribe(onNext: {
print($0, terminator: "")
})
.addDisposableTo(disposeBag)
print()
}
}
--- Example of: deferred ---
123
456
123
456
