@Alex Mamo答案是正确的，您需要一个DocumentReference.

@Alex Mamo answer is right, you need a DocumentReference.

注意:您不能自己创建一个！

您必须通过查询firebase来获得参考！

You have to get the reference by querying firebase!

代码:

return this.auth.currUser
      .pipe(
        take(1),
        switchMap(user => this.afs
            .collection('chats', ref => ref.where('members', 'array-contains', this.afs
              .collection('users')
              .doc<User>(user.uid)
              .ref))
            .snapshotChanges()
            .pipe(
              map(actions => {
                return actions.map(action => {
                  const data = action.payload.doc.data() as Chat;
                  const id = action.payload.doc.id;
                  return {id, ...data};
                });
              })
            ) as Observable<Chat[]>
        )
      );

关键部分是价值"部分，即:

The crucial part is the 'value' part which is:

this.afs
              .collection('users')
              .doc<User>(user.uid)
              .ref

您查询并通过获得参考.

You query and THEN get the reference with .ref!

就是这样！这就是查询DocumentReference的方式！

That's it! That's how you query for a DocumentReference!