firebase - Flutter：根据 Firestore 中的值列表检索数据

Question

谁能告诉我代码有什么问题。该列表包含两项，但该函数只返回第一项，一秒钟后第一项消失：

Stream<List<Forum>> getListOfOwnerCourses() async* {
    FirebaseUser firebaseUser = await FirebaseAuth.instance.currentUser();
    final snap = await Firestore.instance.collection('users').document(firebaseUser.uid).get();
    List<Forum> _courseList = [];
    List myOwnCourses = [];
    if (snap.exists && snap.data['myOwnCourses'] != null) {
      myOwnCourses = snap.data['myOwnCourses'];
      for (String co in myOwnCourses) {
        print("$co Dler");
        var courses = await Firestore.instance.collection('courses').document(co).get();
        Forum forum = Forum.fromSnapshot(courses);
        _courseList.add(forum);
        yield _courseList;
      }
    }
    print("${_courseList[1].title}");
  }

标签： firebasefluttergoogle-cloud-firestorestreamyield