使用 RxJs 和 AngularFirestore 通过外键获取单个文档 [英] Get a single document by foreign key in using RxJs and AngularFirestore

问题描述

我写了一个看起来像这样的查询:

I've written a query that looks like this:

getPaymentByBookingId(id: string): Observable<Payment> {
    return this.afs.collection<Payment>('payments', ref => ref.where('bookingId', '==', id).limit(1))
        .valueChanges()
        .pipe(
            flatMap(array => from(array)),
            first()
        );
}

其中 Payment 对象具有对 Booking id 的唯一引用.我想查找给定 ID 的付款.

Where a Payment object has a unique reference to a Booking id. I want to find the Payment for a given ID.

这似乎是纠正此查询的一种非常复杂的方法.

This seems like quite a convoluted way to right this query.

有没有更简单的方法来做到这一点 - 包括这里是否有代码异味使这变得困难?

Is there a simpler way to do this - including if there is a code smell here that makes this hard?

推荐答案

稍微简单一点的是:

getPaymentByBookingId(id: string): Observable<Payment> {
    return this.afs.collection<Payment>('payments', ref => ref.where('bookingId', '==', id).limit(1))
        .valueChanges()
        .pipe(
            map(array => array[0]),
        );
}

如果未找到付款，这将返回 undefined.

this will returned undefined if the payment is not found.

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