如何使用 Flutter 获取 Firestore 中每个集合的子集合 [英] How to get sub-collections of every collection in Firestore using Flutter

问题描述

我正在构建一个任务管理应用，其中每个用户都有多个项目(集合)，每个项目内部都有任务(集合)，每个任务内部都有子任务.

I'm building a task management app where every user has multiple projects (collections), inside every project there are tasks (collections), and inside every task there are sub-tasks.

我能够使用此代码检索所有项目:

I was able to retrieve all the projects using this code:

User user = Provider.of<User>(context);
CollectionReference projects = Firestore.instance.collection('users').document(user.uid).collection("projects");

但我的问题是如何从每个项目中获取所有任务和子任务(如果存在)并将它们列在 StreamBuilder 中?

But my question is how can I get all the tasks and sub-tasks (if they exist) from every project and list them in a StreamBuilder?

这是我当前的代码:

Flexible(
            child: StreamBuilder<QuerySnapshot>(
              stream: projects.snapshots(),
              builder: (BuildContext context,
                  AsyncSnapshot<QuerySnapshot> snapshot) {
                if (snapshot.hasError) {
                  return Text('Something went wrong');
                }

                if (snapshot.connectionState == ConnectionState.waiting) {
                  return Text("Loading");
                }

                return new ListView(
                  children:
                      snapshot.data.documents.map((DocumentSnapshot document) {
                    return new ListTile(
                      title: new Text(document.data['project_name']),
                      subtitle: new Text(document.data['project_description']),
                    );
                  }).toList(),
                );
              },
            ),
          ),

如果项目有任务我想在项目描述下面显示它们，如果任务有子任务我想在它的父任务下面显示它们.

If the project has tasks I want to display them below the project description, and if the task has sub-tasks I want to show them below its parent task.

推荐答案

听起来您本质上是在问如何列出嵌套的子集合，这对于 Web 和移动客户端来说是不可能的.另见:

It sounds like you're essentially asking how to list nested subcollections, which is not possible for web and mobile clients. See also:

• 如何在 Cloud Firestore 文档中列出子集合
• 如何在 firestore 上列出子集合?

此外，所有 Firestore 查询都很浅，这意味着它们一次只考虑一个集合中的文档.没有深度或递归查询.

Also, all Firestore queries are shallow, meaning they only consider documents in one collection at a time. There are no deep or recursive queries.

考虑在文档中维护项目列表，您可以直接get().您可以使用该列表直接查询每个子集合.

Consider instead maintaining the list of projects in a document that you can get() directly. You can use that list to then query each subcollection directly.

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