type 'Null' is not a subtype of type 'Map' flutter error

Question

I get the error:

'Null' is not a subtype of type 'Map<String, dynamic>' in type cast

 @override
  void initState() {
    FirebaseFirestore.instance.collection('user').doc(widget.id);
    AsyncSnapshot<DocumentSnapshot>? snapshot;
    Map<String, dynamic> data = snapshot?.data!.data() as Map<String, dynamic>;
    
    super.initState();
  }

You arent passing anything on `snapshot` but using on next line — Md. Yeasin Sheikh, Jul 29 '22 at 22:08
You didn't initialize `snapshot` so it's _null_ and on the next line you are trying to convert _null_ to _Map_, it won't work. — belinda.g.freitas, Jul 29 '22 at 23:19
and where are you even using `snapshot` and `data`, it is only scoped inside `initState()` — Alraj, Jul 30 '22 at 07:21

score 1 · Answer 1 · answered Jul 30 '22 at 05:49

snapshot?.data!.data() evaluates to null because snapshot is null. And trying to cast it to a map with as Map<String, dynamic> throws this error.

To fix it use a ternary operator like that (assuming data should not be null):

Map<String, dynamic> data = snapshot?.data?.data() != null
  ? snapshot?.data!.data()! as Map<String, dynamic>
  : <String, dynamic>{};

type 'Null' is not a subtype of type 'Map' flutter error

1 Answers1