RxSwift基本使用（一）

备注：本文参考自田腾飞博文 [RxSwift入坑解读-你所需要知道的各种概念] (http://www.codertian.com/2016/11/27/RxSwift-ru-keng-ji-read-document/)，出于个人学习以及笔记需要特记录下RxSwift基本使用

概念

Observable : 可被观察的，事件源

Observer : 观察者，观察者需要订阅Observable，才能受到其发出的事件

DisposeBag : 相当于iOS中的ARC，会在适当的时候销毁观察者，自动去释放资源

如果需要手动销毁观察者直接调用dispose()方法,例： 
Observable.empty().subscribe { (str:Event) in 
print(“empty:”,str) 
}.dispose()

subscribe : 订阅者，用于订阅sequence发出的事件

基本使用

never

never就是创建一个sequence,但不发出任何事件信号

let bag = DisposeBag()
Observable.never().subscribe { (str :Event<String>) in
print("never:",str) //无
}.addDisposableTo(bag)

备注：为了方便简洁，后续例子中创建bag变量的代码将省略

empty

empty创建一个空的sequence,但只能发出一个completed事件

Observable.empty().subscribe { (str :Event<String>) in
print("empty:",str)
}.addDisposableTo(bag)//empty: completed

just

just创建一个sequence,但只能发出一种特定的事件，能正常结束

Observable.just("just").subscribe { (str :Event<String>) in
print("just:",str)
}.addDisposableTo(bag)//just:next(just)
//just:completed

of

创建一个sequence能发出很多种事件信号

Observable.of("1","2","3").subscribe { (str) in
print("of:",str)
}.addDisposableTo(bag) /**
of: next(1)
of: next(2)
of: next(3)
of: completed
*/ //subscribe onNext 直接取值 Observable.of("1","2","3").subscribe(onNext: { (str) in
print("of2:",str)
}).addDisposableTo(bag) /**
of2: 1
of2: 2
of2: 3
*/

from

from从集合中创建sequence，例如数组，字典或者Set

Observable.from([10,100,1000]).subscribe(onNext: { (num) in
print("from:",num)
}).addDisposableTo(bag) /**
from: 10
from: 100
from: 1000
**/

create

create 自定义可观察的sequence

//create 自定义可观察的sequence
let myObservable = Observable.create { (observer:AnyObserver<Any>) -> Disposable in
observer.onNext("12")
observer.onNext("21")
observer.onNext("123")
observer.onCompleted()
return Disposables.create()
}
myObservable.subscribe { (e:Event<Any>) in
print("myObservable:",e)
}.addDisposableTo(bag) /**
myObservable: next(12)
myObservable: next(21)
myObservable: next(123)
myObservable: completed
**/

range

range 创建一个sequence，会发出这个范围中所有事件

Observable.range(start: 1, count: 5).subscribe(onNext: { (num) in
print("range:",num)
}).addDisposableTo(bag)
/**
range: 1
range: 2
range: 3
range: 4
range: 5
**/

repeatElement

创建一个sequence，发出特定的事件n次

Observable.repeatElement("LouKit").take(3).subscribe { print($0)}.addDisposableTo(bag) //重复发出3次，如果没有take 就无限次
/**
next(LouKit)
next(LouKit)
next(LouKit)
completed
**/

generate

generate是创建一个可观察sequence，当初始化的条件为true的时候，他就会发出所对应的事件

Observable.generate(initialState: 10, condition: {$0 < 15}, iterate: {$0 + 1}).subscribe(onNext: {print("generate",$0)}).addDisposableTo(bag)
/**
generate 10
generate 11
generate 12
generate 13
generate 14
**/

deferred

deferred会为每一为订阅者observer创建一个新的可观察序列

var index = 1
let deferred = Observable<String>.deferred{ print("index:",index)
index += 1 return Observable.create{ observer in
observer.onNext("1")
observer.onNext("2")
observer.onCompleted()
return Disposables.create()
}
} deferred.subscribe { print("调用1:",$0)}.addDisposableTo(bag) deferred.subscribe { print("调用2:",$0)}.addDisposableTo(bag) /**
index: 1
调用1: next(1)
调用1: next(2)
调用1: completed
index: 2
调用2: next(1)
调用2: next(2)
调用2: completed
**/

do

主要用于在subscribe中onNext，onError，onCompleted前调用

Observable.just("00").do(onNext: {print("doOnNext:",$0)},onError: {print("doOnError:",$0)},onCompleted: {print("doOnCompleted:")})
.subscribe(onNext: { (str) in
print("onNext:",str)
}, onError: { (error) in
print("onError")
}, onCompleted: {
print("onCompleted")
}).addDisposableTo(bag) /**
doOnNext: 00
onNext: 00
doOnCompleted:
onCompleted
**/

Subjects

Subjet是observable和Observer之间的桥梁，一个Subject既可以充当Obserable也可以充当Observer，即它可以发出事件，也可以监听事件

PublishSubject

采用PublishSubject订阅事件的时候，只能接收到订阅他之后发生的事件

let publicSubject = PublishSubject<String>()
publicSubject.onNext("A")
publicSubject.onNext("B")
publicSubject.subscribe(onNext: {print("publicSubject:",$0)}) .addDisposableTo(bag)
publicSubject.onNext("C")
publicSubject.onNext("D") /**
publicSubject: C
publicSubject: D
**/

ReplaySubject

可以接收到订阅他之后以及之前发生的事件,对于要接受几个以前的事件取决于bufferSize设置的大小

let replaySubject = ReplaySubject<String>.create(bufferSize: 2)
replaySubject.onNext("A")
replaySubject.onNext("B")
replaySubject.onNext("C")
replaySubject.onNext("D")
replaySubject.subscribe(onNext: {print("replaySubject:",$0)}) .addDisposableTo(bag)
replaySubject.onNext("E")
replaySubject.onNext("F")
replaySubject.onNext("G")
/**
replaySubject: C
replaySubject: D
replaySubject: E
replaySubject: F
replaySubject: G
**/ //接受全部的事件
let replaySubject2 = ReplaySubject<String>.createUnbounded()
replaySubject2.onNext("A")
replaySubject2.onNext("B")
replaySubject2.subscribe(onNext: {print("replaySubject2:",$0)}) .addDisposableTo(bag)
replaySubject2.onNext("E")
replaySubject2.onNext("F") /**
replaySubject2: A
replaySubject2: B
replaySubject2: E
replaySubject2: F
**/

BehaviorSubject

采用BehaviorSubject订阅事件，会接收到订阅之前的最后一个事件以及订阅之后所有事件。

let behavior = BehaviorSubject(value: "behavior")
behavior.onNext("A")
behavior.onNext("B")
behavior.subscribe(onNext: {print("behavior:",$0)}).addDisposableTo(bag)
behavior.onNext("C")
behavior.onNext("D") /**
behavior: B
behavior: C
behavior: D
**/

Variable

Variable是对BehaviorSubject一个包装；

Variable当成Obserable, 让订阅者进行订阅时, 需要asObserable转成Obserable；

Variable发出事件, 直接修改对象的value即可;

当事件结束时,Variable会自动发出completed事件

let variable = Variable("variable") variable.value = "A"
variable.value = "B"
variable.asObservable().subscribe { (event:Event<String>) in
print("variable:",event)
}.addDisposableTo(bag)
variable.value = "C"
variable.value = "D" /**
variable: next(B)
variable: next(C)
variable: next(D)
variable: completed
**/

联合操作

联合操作就是把多个Observable流合成单个Observable流

startWith

在发出事件消息之前，先发出某个特定的事件消息。

Observable.of(1,2).startWith(3).subscribe(onNext: {print($0)}).addDisposableTo(bag) /**
3
1
2
**/

merge

将多个Observable流合成单个Observable流，然后任何一个Observable发出事件都能被接收到

let sub1 = PublishSubject<String>()
let sub2 = PublishSubject<String>() Observable.of(sub1,sub2).merge().subscribe(onNext: { print($0) }).addDisposableTo(bag)
sub1.onNext("sub1-1")
sub1.onNext("sub1-2") sub2.onNext("sub2-1")
sub1.onNext("sub1-2")
sub2.onNext("sub2-2")
/**
sub1-1
sub1-2
sub2-1
sub1-2
sub2-2
**/

zip

将多个Observable流合成单个Observable流，只有当多个Observable流同时发出事件时，并且把多个Observable流的内容合并成一个元组，才会触发压缩流的事件。

let zip1 = PublishSubject<String>()
let zip2 = PublishSubject<String>() Observable.zip(zip1,zip2){ zip1,zip2 in
"\(zip1) \(zip2)"
}.subscribe(onNext: { print($0) })
.addDisposableTo(bag) zip1.onNext("zip1-1")
zip1.onNext("zip1-2")
zip2.onNext("zip2-1")
zip2.onNext("zip2-2") /**
zip1-1 zip2-1
zip1-2 zip2-2
**/

注意：merge、zip都能将多个Observable流合成单个Observable流，但合并后前者任何一个Observable发出事件都能被接收到，后者必须是多个流同时发出事件时才被接收到

combineLatest

将多个Observable流合并起来 并拿到其各个流的最新值,即每个合并的signal至少都有过一次onNext，才会触发合并的流

let ps1 = PublishSubject<String>()
let ps2 = PublishSubject<String>() Observable.combineLatest(ps1, ps2) { element1, element2 in
"\(element1) \(element2)"
}
.subscribe(onNext: { print($0) })
.addDisposableTo(bag) ps1.onNext("ps1-01")
ps1.onNext("ps1-02")
ps2.onNext("ps2-01") /**
ps1-02 ps2-01
**/

switchLatest

用于对事件流进行转换，即一个Observable中的内容还是Observable。(个人理解)

let bs1 = BehaviorSubject(value: "1")
let bs2 = BehaviorSubject(value: "A") let variable = Variable(bs1)
variable.asObservable().switchLatest().subscribe(onNext: {print($0)}).addDisposableTo(bag)
bs1.onNext("2")
variable.value = bs2
bs1.onNext("3")
bs2.onNext("B")
/**
1
2
A
B
**/