flutter - infinite loop on a finite array

Issue

I don't understand why the result of my code is an infinite loop.

class _SearchUserState extends State<SearchUser> {
  List usernames = [];

 @override
  Widget build(BuildContext context) {
    var invitedBy = widget.snapshot.data()["invitedBy"];
    final FirebaseFirestore _firestore = FirebaseFirestore.instance;
    invitedBy.forEach((userId) async {
      try {
        var snap = await _firestore.collection('users').doc(userId).get();
        var username = snap.data()!["username"];
        print(username);
        setState(() {
          usernames.add(username);
        });
      } catch (err) {
        print(err);
      }
    });

 Text("invitedBy length ${invitedBy.length}"),
        Text("usernames length ${usernames.length}")

For the two last lines of code i get :"invitedBy length 1" , "usernames length + infinite number"

Solution

You're calling setState inside your build method. That triggers another build, and setState is called again, and so on...

Answered By - Kirill Bubochkin