Solution :
Code Example :
import 'package:cloud_firestore/cloud_firestore.dart';
class ModelClassName {
  final String id;
  final String Name;
  bool isAdmin;
  ModelClassName({
    this.id,
    this.Name,
    this.isAdmin
  });
  factory ModelClassName.fromDocument(DocumentSnapshot doc) {
    bool isAdmin = false;
    try {
      isAdmin = doc.get("isAdmin");
    } on Exception catch (exception) {
      isAdmin=false;
    } catch (error) {
      isAdmin=false;
    }
    return ModelClassName(
        id: doc.reference.id,
        Name: doc.get("Name"),
        isAdmin: isAdmin,
    );
  }
}