flutter - 使用Flutter Firestore插件，对文档中的每个子集合进行操作(Using Flutter Firestore plug in, do something for each sub collection in a document)

Question

To help me better understand Flutter and Firebase, I'm making a list sharing app.

(为了帮助我更好地理解Flutter和Firebase，我正在制作一个列表共享应用程序。)

I'm working on the list home screen that will show a reorderable list tile view with a tile for each of the users' lists, I have not began to work on whats inside of these lists.

(我正在使用列表主屏幕，该屏幕将显示一个可重新排序的列表图块视图，其中包含每个用户列表的图块，但我尚未开始研究这些列表中的内容。)

I have firestore set up so that each list is a sub collection, now I want to create a tile for each sub collection in that user's document ( a list of that user's lists).

(我设置了Firestore，以便每个列表都是一个子集合，现在我想为该用户文档中的每个子集合（该用户列表的列表）创建一个磁贴。)

I'm having a tough time telling flutter to do something for each sub collection without using a specific sub collection's name.

(我很难告诉flutter为每个子集合做一些事情而不使用特定子集合的名称。)

I wanted to pass in a list title to each tile by making a collection reference for each sub collection( list) and calling .id on each one.

(我想通过为每个子collection（list）设置collection引用并在每个sub.call上调用.id来向每个tile传递列表标题。)

Using the collection ID as the title, I'm not yet sure if I can do this or if ill have to make the list title a field inside of each list.

(使用集合ID作为标题，我不确定是否可以执行此操作，或者是否必须使列表标题成为每个列表中的一个字段。)

Either way, I need to find out how to do something for each subcollection inside a particular document.

(无论哪种方式，我都需要找出如何为特定文档中的每个子集合做一些事情。)

.forEach seems to only work on document fields, not subcollections?

(.forEach似乎仅适用于文档字段，而不适用于子集合？)

What am I doing wrong?

(我究竟做错了什么？)

I'm sure there is a better way to go about this.

(我相信有更好的方法可以解决此问题。)

I have not included any code as this is a big picture kind of question.

(我没有包含任何代码，因为这是一个大问题。)

  ask by BlueOverBrown translate from so

Answer 1

There is no method in the Firestore client-side SDKs to get all collections (or subcollections under a specific document).

(Firestore客户端SDK中没有方法来获取所有集合（或特定文档下的子集合）。)

Such API does exist in the server-side SDKs, but not in the client-side SDKs.

(这样的API 确实存在于服务器端SDK中，但不存在于客户端SDK中。)

See:

(看到：)

• Fetching all collections in Firestore

  (在Firestore中获取所有集合)

• How to get all of the collection ids from document on Firestore?

  (如何从Firestore上的文档中获取所有集合ID？)

So you'll need to know the collections already, typically by changing your data model.

(因此，您通常需要通过更改数据模型来了解集合。)

For example by creating a document for each list's metadata, and then storing the list items in a subcollection with a known name under that document.

(例如，通过为每个列表的元数据创建一个文档 ，然后将列表项存储在该文档下具有已知名称的子集合中。)

That way you can get all lists by querying for the documents, which is possible within the API.

(这样，您可以通过查询文档来获取所有列表，这在API中是可能的。)