Firestore fetch never executes in Flutter Code

Question

I have an int named "length" in my code and I am trying to change it's value from a field in my Cloud Firestore:

 int length;
_handlePressed(context) {
    DocumentReference postReference =  Firestore.instance.collection(ISBN).document(post);

    postReference.get().then((datasnapshot){
      if(datasnapshot.exists) {
        length = datasnapshot.data["length"];
        print(length.toString());
      }
    });
}

The field "length" is stored as a Number Type in my Firestore.

The problem is that the print operation does not execute and printing length elsewhere shows null in the console. What am i missing?

Answer 1

First, make sure that _handlePressed is really called then update the state with setState when using a StatefulWidget:

int length; 
_handlePressed(context) { 
    DocumentReference postReference = Firestore.instance.collection(ISBN).document(post); 
    postReference.get().then((datasnapshot){ 
    if(datasnapshot.exists) { 
        setState(()
            length = datasnapshot.data["length"];
        );
    print(length.toString()); 
} }); }