是否有必要取消订阅由 Http 方法创建的 observable? [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，您不需要.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:

注意它在获得结果后如何运行complete().这意味着它实际上在完成时取消订阅.所以你不需要自己做.

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.

这是一个验证测试:

  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);
    };
}

正如预期的那样，您可以看到它总是在获取结果并完成可观察操作符后自动取消订阅.这发生在超时 (#3) 时，因此我们可以在所有完成和完成后检查 observable 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，当 Ng2 自动取消订阅时，不会存在泄漏！

So, no leak would exist as Ng2 auto unsubscribes!

很高兴提到:这个 Observable 被归类为 finite，与 infinite Observable 相反，它是例如，可以像 DOM click 侦听器一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.

感谢@rubyboy 对此的帮助.

THANKS, @rubyboy for help on this.

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