使用takeUntil()关闭条件的订阅

问题描述

我有一个订阅，可以从NgRx减速器获取提供程序.我想使用takeUntil()自动关闭订阅，直到最终返回具有内容的数组:

I have a subscription to get providers from a NgRx reducer. I want to use takeUntil() to automatically close the subscription when is finally returns an array that has content:

// Fetch providers
this.store.pipe(select(reducer.getProviders))
//  .takeUntil(reducer.getProviders.length > 0)
    .subscribe(providers => {
        if (providers) {
            this.providers = providers;
//          takeUntil(/** something **/);
        }
    });

有人可以帮我吗?

我不知道如何使用takeUntil()

推荐答案

takeUntil接受一个Observable. (来源:文档).对于您的情况，使用takeWhile更有意义，只要满足特定条件，它就会发出值(来源:文档).将可选的inclusive属性设置为true，以便它还会发出未通过谓词的第一项.

takeUntil accepts an Observable. (Source: docs). For your case, it would make more sense to use takeWhile, this will emit values as long as a particular condition is satisfied (Source: docs). Set the optional inclusive property to true so that it will also emit the first item that didn't pass the predicate.

this.store.pipe(select(reducer.getProviders))
    .takeWhile(reducer => reducer.getProviders.length == 0, true)
    .subscribe(providers => {
        if (providers) {
            this.providers = providers;
        }
    });

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