前言
将观察序列的元素值就行筛选的操作
Filtering and Conditional Operators
-
filter
将符合条件的元素值根据条件进行筛选
example("filter") {
let disposeBag = DisposeBag()
Observable.of(
"🐱", "🐰", "🐶",
"🐸", "🐱", "🐰",
"🐹", "🐸", "🐱")
.filter {
$0 == "🐱"
}
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- filter example ---
🐱
🐱
🐱
-
distinctUntilChanged
去掉序列中重复的事件元素，相邻元素如果相同的话，进保留一个，如果不是相邻的元素不做去重元素
example("distinctUntilChanged") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐷", "🐱", "🐱", "🐱", "🐵", "🐱")
.distinctUntilChanged()
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- distinctUntilChanged example ---
🐱
🐷
🐱
🐵
🐱
-
elementAt
筛选出序列中指定索引的元素
example("elementAt") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
.elementAt(3)
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- elementAt example ---
🐸
-
single
分两种情况筛选，当single后面不带条件的时候，则默认筛选第一个元素抛出；single后面带条件就根据条件进行进行筛选，如果元素不是唯一一个或者没有符合条件的元素将抛出错误
/*********single 不带条件***********/
example("single") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
.single()
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- single example ---
🐱
/*********single 带条件***********/
example("single with conditions") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
.single { $0 == "🐸" }
.subscribe { print($0) }
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- single with conditions example ---
next(🐸)
completed
/*********single 带条件，筛选值不唯一***********/
example("single with conditions") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐱", "🐰", "🐶")
.single { $0 == "🐰" }
.subscribe { print($0) }
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- single with conditions example ---
next(🐰)
error(Sequence contains more than one element.)
/*********single 带条件，筛选值没有的情况 *****/
example("single with conditions") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
.single { $0 == "🔵" }
.subscribe { print($0) }
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- single with conditions example ---
error(Sequence doesn't contain any elements.)
-
take
仅从可观察序列的开头发出指定数量的元素
example("take") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
.take(3)
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- take example ---
🐱
🐰
🐶
-
takeLast
仅从可观察序列的结尾倒数发出指定数量的元素
example("takeLast") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
.takeLast(3)
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
example("takeLast") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
.takeLast(3)
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
-
takeWhile
仅从可观察序列的开头筛选出指定条件的元素
example("takeWhile") {
let disposeBag = DisposeBag()
Observable.of(1, 2, 3, 4, 5, 6)
.takeWhile { $0 < 4 }
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- takeWhile example ---
1
2
3
-
takeUntil
A序列元素等到B序列元素发出元素以后再发出，A序列的事件发送完以后就发发送Complete，B序列无论是否发出新的事件元素以后A序列都不再发出事件元素
example("takeUntil") {
let disposeBag = DisposeBag()
let sourceSequence = PublishSubject<String>()
let referenceSequence = PublishSubject<String>()
sourceSequence
.takeUntil(referenceSequence)
.subscribe { print($0) }
.disposed(by: disposeBag)
sourceSequence.onNext("🐱")
sourceSequence.onNext("🐰")
sourceSequence.onNext("🐶")
referenceSequence.onNext("🔴")
sourceSequence.onNext("🐸")
sourceSequence.onNext("🐷")
sourceSequence.onNext("🐵")
}
// 控制台打印的结果：
--- takeUntil example ---
next(🐱)
next(🐰)
next(🐶)
completed
-
skip
和take作用相反，仅从可观察序列的开头禁止发出或者排除指定数量的元素
example("skip") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
.skip(2)
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- skip example ---
🐶
🐸
🐷
🐵
-
skipWhile
和takeWhile相反，仅从可观察序列的开头排除出指定条件的元素
example("skipWhile") {
let disposeBag = DisposeBag()
Observable.of(1, 2, 3, 4, 5, 6)
.skipWhile { $0 < 4 }
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- skipWhile example ---
4
5
6
-
skipWhileWithIndex
根据索引的条件排除相应的元素
example("skipWhileWithIndex") {
let disposeBag = DisposeBag()
Observable.of("🐱", "🐰", "🐶", "🐸", "🐷", "🐵")
.skipWhileWithIndex { element, index in
index < 3
}
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
}
// 控制台打印的结果：
--- skipWhileWithIndex example ---
🐸
🐷
🐵
-
skipUntil
和takeUntil相反，A序列事件元素，排除在B序列发出事件元素之前的时间元素，保留B序列发出元素之后的A的事件元素
example("skipUntil") {
let disposeBag = DisposeBag()
let sourceSequence = PublishSubject<String>()
let referenceSequence = PublishSubject<String>()
sourceSequence
.skipUntil(referenceSequence)
.subscribe(onNext: { print($0) })
.disposed(by: disposeBag)
sourceSequence.onNext("🐱")
sourceSequence.onNext("🐰")
sourceSequence.onNext("🐶")
referenceSequence.onNext("🔴")
sourceSequence.onNext("🐸")
sourceSequence.onNext("🐷")
sourceSequence.onNext("🐵")
}
// 控制台打印的结果：
--- skipUntil example ---
🐸
🐷
🐵
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