Question

我有一个getDimensions方法，该方法返回一个Observable<string[]>。

dimension.service.ts

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

reloader.service.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update方法中调用此方法。问题是，我不知道如何正确退订getDimensions。一种可能的解决方案是创建一个Subscription，然后在OnDestroy中调用unsubscribe，但是对我来说，这不是一个好的解决方案：

这是我在整个应用程序中使用的服务，因此OnDestroy钩子永远不会发生
我每update秒调用一次n方法，因此每n秒就会有一个新的订阅

可能的解决方案： （不好）

reloader.service.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，如果可观察对象完成（这是我的情况），则无需退订。

Answer 1

如果您希望在数据或可观察到的数据完整时退订

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 

}

Answer 2

订阅的添加功能可能无法执行您想要的操作。在文档中指出以下内容。

   /**
     * 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;

我猜您想取消订阅idsToUpdate。您可以像平常一样保留订阅的引用，然后执行sub.unsubscribe()

以下是修改代码的示例

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();

}

如何正确退订这种可观察的内容

2 个答案: