await Function does not return a value

Question

I have created function get user and set it's data from firestore, this is the code of function getUser.

  Future<User> getUser(String uid) async{
    User user;
    _firestore
        .collection(USERS_COLLECTION)
        .where("uid", isEqualTo: uid.toString())
        .getDocuments()
        .then((doc) {
      _firestore
          .document('/$USERS_COLLECTION/${doc.documents[0].documentID}')
          .get()
          .then((userData) {

        user = User(
          name: userData.data["name"],
          username: userData.data["username"],
          profilePhoto: userData.data["profilePic"],
        );


      }).catchError((e) {
        print(e);
      });
    });

    return user;

  }

Then I have my profile page I have created function to set user from getUser() to current user like this:

User me;
String myUID = "t4skPFRXcLPxAWvhHpaiPOfsrPI3";

    @override
      void initState() {
        super.initState();
        setUser();
      }
         ......

Future<void> setUser() async{
    me = await userManagment.getUser(myUID);
  }

But when I try to use print for example print(me.name) does not anything happen, when I try to set url of networkImage to me.profilePhoto there is an error showing tell me the url it's null.

Does this answer your question? What is a Future and how do I use it? — Christopher Moore
– Christopher Moore, Commented Feb 2, 2021 at 18:07
@ChristopherMoore I have done everything like all instructions inside your link but If there are things should I do tell me or something I done it in wrong way tell me. — Abdullrahman Wasfi
– Abdullrahman Wasfi, Commented Feb 2, 2021 at 18:14

Christopher Moore · Accepted Answer · 2021-02-02 18:18:37Z

Don't mix async-await and .then syntax. It's something that can be done, but it will more likely confuse than help. Adding the async modifier to your function is doing nothing since your function does not use await.

Consider the following options:

With .then

Future<User> getUser(String uid) {
    return _firestore
        .collection(USERS_COLLECTION)
        .where("uid", isEqualTo: uid.toString())
        .getDocuments()
        .then((doc) {
      return _firestore
          .document('/$USERS_COLLECTION/${doc.documents[0].documentID}')
          .get()
          .then((userData) {

        return User(
          name: userData.data["name"],
          username: userData.data["username"],
          profilePhoto: userData.data["profilePic"],
        );


      }).catchError((e) {
        print(e);
      });
    });
  }

With async-await

Future<User> getUser(String uid) async{
    User user;

    try{
    var doc = await _firestore
        .collection(USERS_COLLECTION)
        .where("uid", isEqualTo: uid.toString())
        .getDocuments();
    
    var userData = await _firestore
          .document('/$USERS_COLLECTION/${doc.documents[0].documentID}')
          .get();

    user = User(
          name: userData.data["name"],
          username: userData.data["username"],
          profilePhoto: userData.data["profilePic"],
        );
    }
    catch(e) {
      print(e);
    }
    return user;

  }

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