示例 1:
var obsNumber = /* observable that produce numbers */;
var obsText1 = /* observable that produce text */;
var obsText2 = /* observable that produce text */;
var obsContext = /* IF obsNumber < 5 THEN obsText1 ELSE obsText2 */;
obsContext
是一个 observable,它将根据 obsNumber
的值从 obsText1
或 obsText2
返回数据>.
示例 2:
var arrOfObservables = /* an array of observables */;
var obsNumber = /* observable that produce numbers */;
var obsSelect = /* arrOfObservables[obsNumber] */;
obsSelect
是一个 observable,它将返回来自 arrOfObservables
数组的选定 observable 的数据,该数组由 obsNumber
产生的值确定。
我不知道如何使用 RxJS 指定此行为。在我看来,我需要能够在多个可观察对象之间动态订阅/取消订阅。
如何使用 RxJS 让这两个示例工作?
最佳答案
使用switch
:
Transforms an observable sequence of observable sequences into an observable sequence producing values only from the most recent observable sequence.
示例 1
var obsNumber,
obsText1,
obsText2;
obsNumber = Rx.Observable.interval(500).take(10);
obsText1 = Rx.Observable.return('a');
obsText2 = Rx.Observable.return('b');
obsNumber
.do(function (x) {
console.log('x: ' + x);
})
.map(function (x) {
return x < 5 ? obsText1 : obsText2;
})
.switch()
.subscribe(function (context) {
console.log('context: ' + context);
});
<script src='https://rawgit.com/Reactive-Extensions/RxJS/v.2.5.3/dist/rx.all.js'></script>
示例 2
var obsNumber,
arrOfObservables;
obsNumber = Rx.Observable.range(0, 3);
arrOfObservables = [
Rx.Observable.return('a'),
Rx.Observable.return('b'),
Rx.Observable.return('c')
];
obsNumber
.do(function (x) {
console.log('x: ' + x);
})
.map(function (x) {
return arrOfObservables[x];
})
.switch()
.subscribe(function (context) {
console.log('context: ' + context);
});
<script src='https://rawgit.com/Reactive-Extensions/RxJS/v.2.5.3/dist/rx.all.js'></script>
关于reactive-programming - 将可观察序列转换为仅从最近的可观察序列产生值的可观察序列,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/17362902/