Question

在下面的示例中，每次onNext调用都会调用map两次，这是不必要的，因为ds的相同值可以重复用于两个观察者。如何编写代码，使每个onNext调用只调用一次映射？或者我应该使用诺言？

var subject = new Rx.BehaviorSubject(42);

var ds = subject.map(function(x) {
        console.log("processing");
        return x + 100;
});

var subscription1 = ds.subscribe(
    function (x) {
        console.log('first observed: ' + x.toString());
    }
);

var subscription2 = ds.subscribe(
    function (x) {
        console.log('second observed: ' + x.toString());
    }
);

subject.onNext(56);
subject.onNext(134);

Answer 1

最简单的方法是分享＆＃34;分享＆＃34;通过share运营商订阅。

这是最简单的方法：

var subject = new Rx.BehaviorSubject(42);

var ds = subject.map(function(x) {
        console.log("processing");
        return x + 100;
}).share();

var subscription1 = ds.subscribe(
    function (x) {
        console.log('first observed: ' + x.toString());
    }
);

var subscription2 = ds.subscribe(
    function (x) {
        console.log('second observed: ' + x.toString());
    }
);

subject.onNext(56);
subject.onNext(134);

// => processing
// => first observed: 142
// => processing
// => first observed: 156
// => second observed: 156
// => processing
// => first observed: 234
// => second observed: 234

当一次足够时，RxJs反应图被调用两次

1 个答案: