RxJs:如何基于observable的状态循环？

预期的产出是:

Counter: 3
Counter: 2
Counter: 1
Counter: 0
Next: YESS!
Completed

假设这是一个可解决的问题,我不清楚如何标记循环时想要返回的"开始".

有一个扩展运算符,通过允许您递归调用选择器函数来使您关闭.在这种情况下,返回一个空的observable将是你的休息.见jsbin:

var source = Rx.Observable.return({val: 0, counter: 3})
    .expand(value =>  { 
      if(!value.counter) return Rx.Observable.empty();
      value.counter -= 1;
      if(!value.counter) value.val = 'YESS';
      return Rx.Observable.return(value)
    })
    .subscribe(value => console.log(value.counter ? 
                                    'Counter: ' + value.counter : 
                                    'Next: ' + value.val));

不完全是你想要的但是关闭,使用expand运算符和信令结束递归Rx.Observable.empty(http://jsfiddle.net/naaycu71/3/):

var source = new Rx.Observable.of({val: 0, counter: 3});

source.expand(function(o) {
  console.log('Counter: ' + o.counter);
  o.counter--;

return (o.counter >= 0) ? Rx.Observable.just(o) : Rx.Observable.empty()
})
.subscribe(
    function (x) {
        console.log('Next: ' , x);
    },
    function (err) {
        console.log('Error: ' + err);   
    },
    function () {
        console.log('Completed');   
    });

输出:

Next:  Object {val: 0, counter: 3}
Counter: 3
Next:  Object {val: 0, counter: 2}
Counter: 2
Next:  Object {val: 0, counter: 1}
Counter: 1
Next:  Object {val: 0, counter: 0}
Counter: 0
Completed