如何从Firestore中的两个集合中获取数据？
[英]How do I get data from two collections in firestore?
问题描述
I have the following problem. 
我有以下问题。 I try to manage an to m structure with firebase. 我尝试使用firebase管理一个to m结构。 Therefore i made three collections. 因此，我做了三个收藏。 collections |-----cards |----name |----text |-----cardlist |----name |----numberOfCards |-----card_cardList |----cardId |----cardListId |----number
Now I have the id of a cardList and my goal is to get all the cards which are in this list. 现在我有了cardList的ID，我的目标是获取此列表中的所有卡。 To get them from the card_list collection i made this collection('card_list', q => q.where('cardListId', '==', myId) . After that i should somehow map the value number with the cards values which I need to get somehow. 为了从card_list集合中获取它们，我创建了这个collection('card_list', q => q.where('cardListId', '==', myId) 。之后，我应该以某种方式将值number与我所使用的card值进行映射需要某种方式。
Does anyone have a suggestion how to do this? 有人建议如何做吗？
Edited: card_cardList is the collection which shows the n to m relation between cards and cardlist 编辑： card_cardList是一个集合，它显示卡和cardlist之间的n到m关系
1 个解决方案
解决方案1
0 已采纳 2019-01-10 08:05:10
According to the comments: 根据评论：
Q: So you want to get all the cards which are in this list in a single go?
A: Yes thats the plan.
You need to know that Firestore does not have any API to get documents from multiple collections in a single step. 你需要知道，公司的FireStore 没有任何API从多个集合文件在一个单一的步骤。 You will have to use two (or more) separate calls. 您将必须使用两个（或更多）单独的呼叫。 In your particular case, you should create one to get the documents under cards collection, and another one to get the documents in the cardlist collection based on the relationship between them. 在您的特定情况下，您应该创建一个以将文件收集到cards集合中，然后根据它们之间的关系创建另一个以将文件收集到cards cardlist集合中。
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