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如何正确取消订阅此类obervable

rxjs typescript angular

Runtime Terror · 技术社区 · 6 年前

我有一个 getDimensions 返回 Observable<string[]> .

尺寸.服务.ts

public getDimensions(id: string): Observable<string[]> {
    return this.service.loadDimensions(id);
}

重新加载服务.ts

public update(idsToUpdate: string[]): void {

    idsToUpdate.map(id => this.dimensionService.getDimensions(id)).pipe(
        map(
             newDimensions => this.updateDimensions(newDimensions)
        )
    ).subscribe(); // ToDo: unsubscribe

}

然后在应用程序的另一部分,我在内部调用这个方法 update 方法。问题是,我不知道如何正确取消订阅 获取维度 . 一个可能的解决方案是,创建一个 Subscription 然后在 OnDestroy 呼叫取消订阅,但对我来说这不是一个好的解决方案:

这是一个服务,我在整个应用程序中使用它,因此 OnDestroy公司 钩子永远不会发生
我打电话给 更新 方法间隔 n 秒,所以每一秒 n 秒新订阅

可能的解决方案: (不好)

重新加载服务.ts

private subscriptions: Subscription = new Subscription();

...
...

public update(idsToUpdate: string[]): void {

    const sub = idsToUpdate.map(id => this.dimensionService.getDimensions(id)).pipe(
        map(
             newDimensions => this.updateDimensions(newDimensions)
        )
    ).subscribe(); // ToDo: unsubscribe

    this.subscription.add(sub);

}

...
...

public onDestroy(): void {
    this.subscription.unsubscribe();
}

编辑:

正如@jgerstle在他的评论中提到的那样,如果观察表完成(这是我的情况),就不需要取消订阅。

2 回复 | 直到 6 年前

Muhammed Albarmavi 6 年前

如果您想在获得数据或可观察数据完成后取消订阅

public update(idsToUpdate: string[]): void {

    const sub = idsToUpdate.map(id => this.dimensionService.getDimensions(id)).pipe(
        map(
             newDimensions => this.updateDimensions(newDimensions)
        )
    ).subscribe(() => sub.unsubscribe() ); // or you can use complate 

}

John 6 年前

订阅的添加功能可能不会执行您尝试执行的操作。从文件中可以看出以下情况。

   /**
     * Adds a tear down to be called during the unsubscribe() of this
     * Subscription.
     *
     * If the tear down being added is a subscription that is already
     * unsubscribed, is the same reference `add` is being called on, or is
     * `Subscription.EMPTY`, it will not be added.
     *
     * If this subscription is already in an `closed` state, the passed
     * tear down logic will be executed immediately.
     *
     * @param {TeardownLogic} teardown The additional logic to execute on
     * teardown.
     * @return {Subscription} Returns the Subscription used or created to be
     * added to the inner subscriptions list. This Subscription can be used with
     * `remove()` to remove the passed teardown logic from the inner subscriptions
     * list.
     */
    add(teardown: TeardownLogic): Subscription;

我猜你想做的是退订 idsToUpdate -订阅。您可以像这样保留订阅的引用,然后执行 sub.unsubscribe()

下面是一个修改代码的示例

private sub: Subscription;

...
...

public update(idsToUpdate: string[]): void {

    this.sub = idsToUpdate.map(id => this.dimensionService.getDimensions(id)).pipe(
        map(
             newDimensions => this.updateDimensions(newDimensions)
        )
    ).subscribe(); // ToDo: unsubscribe

}

...
...

public onDestroy(): void {
    if(this.sub) this.sub.unsubscribe();

}