是否需要退订Http方法创建的可观察对象? [英] Is it necessary to unsubscribe from observables created by Http methods?

问题描述

您是否需要取消订阅Angular 2 http调用以防止内存泄漏?

Do you need to unsubscribe from Angular 2 http calls to prevent memory leak?

 fetchFilm(index) {
        var sub = this._http.get(`http://example.com`)
            .map(result => result.json())
            .map(json => {
                dispatch(this.receiveFilm(json));
            })
            .subscribe(e=>sub.unsubscribe());
            ...

推荐答案

所以答案是否定的，不是. Ng2会自行清理.

So the answer is no, you don't. Ng2 will clean it up itself.

Http服务源，来自Angular的Http XHR后端源:

The Http service source, from Angular's Http XHR backend source:

在获取结果后，请注意它如何运行complete().这意味着它实际上会在完成订阅后退订.因此，您不需要自己做.

Notice how it runs the complete() after getting the result. This means it actually unsubscribes on completion. So you don't need to do it yourself.

这是一个可以验证的测试:

Here is a test to validate:

  fetchFilms() {
    return (dispatch) => {
        dispatch(this.requestFilms());

        let observer = this._http.get(`${BASE_URL}`)
            .map(result => result.json())
            .map(json => {
                dispatch(this.receiveFilms(json.results));
                dispatch(this.receiveNumberOfFilms(json.count));
                console.log("2 isUnsubscribed",observer.isUnsubscribed);
                window.setTimeout(() => {
                  console.log("3 isUnsubscribed",observer.isUnsubscribed);
                },10);
            })
            .subscribe();
        console.log("1 isUnsubscribed",observer.isUnsubscribed);
    };
}

按预期，您可以看到在获得结果并完成可观察到的运算符后，它总是自动取消订阅.这是在超时(#3)上发生的，因此我们可以检查可观察对象全部完成和完成的状态.

As expected, you can see that it is always unsubscribed automatically after getting the result and finishing with the observable operators. This happens on a timeout (#3) so we can check the status of the observable when it's all done and completed.

结果

因此，由于Ng2自动取消订阅，不会存在泄漏！

So, no leak would exist as Ng2 auto unsubscribes!

值得一提的是:此Observable被归类为finite，与infinite Observable相反，它可以像DOM click侦听器那样发出无限的数据流.

Nice to mention: This Observable is categorized as finite, on contrary to the infinite Observablewhich is an infinite stream of data can be emitted like DOM click listener for example.

谢谢，@ ruby​​boy对此提供了帮助.

THANKS, @rubyboy for help on this.

这篇关于是否需要退订Http方法创建的可观察对象?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！