update

lib/pages/discount/model/discount_model.dart

@@ -11,13 +11,13 @@ import 'package:logging/logging.dart';
 class DiscountModel extends BaseModel {
   final log = Logger('DiscountModel');
 
-  StreamSubscription<QuerySnapshot> listener;
+  StreamSubscription<QuerySnapshot>? listener;
 
   List<Discount> _discounts = [];
   List<Discount> get discounts =>
       _selectedIndex == 1 ? _discounts : List<Discount>.from(_used.values);
 
-  Paginator _used;
+  late Paginator _used;
   bool isLoading = false;
   int _selectedIndex = 1;
   set selectedIndex(int index) {
@@ -25,14 +25,14 @@ class DiscountModel extends BaseModel {
     notifyListeners();
   }
 
-  get selectedIndex => _selectedIndex;
+  int get selectedIndex => _selectedIndex;
 
   initData() {
     _selectedIndex = 1;
     _load();
 
     if (_used != null) _used.close();
-    _used = _getUsed();
+    if (_getUsed() != null) _used = _getUsed()!;
     _used.load();
   }
 
@@ -42,7 +42,7 @@ class DiscountModel extends BaseModel {
   }
 
   _load() {
-    if (listener != null) listener.cancel();
+    if (listener != null) listener!.cancel();
     try {
       listener = Firestore.instance
           .collection("/$discounts_collection")
@@ -60,7 +60,7 @@ class DiscountModel extends BaseModel {
     }
   }
 
-  Paginator _getUsed() {
+  Paginator? _getUsed() {
     if (user == null || !user.hasFcsShipments()) return null;
 
     var pageQuery = Firestore.instance
@@ -73,7 +73,7 @@ class DiscountModel extends BaseModel {
     return paginator;
   }
 
-  Future<List<Discount>> getDiscount(String userID) async {
+  Future<List<Discount>?> getDiscount(String userID) async {
     String path = "/$discounts_collection";
     try {
       var q = Firestore.instance
@@ -113,7 +113,7 @@ class DiscountModel extends BaseModel {
 
   @override
   logout() async {
-    if (listener != null) await listener.cancel();
+    if (listener != null) await listener!.cancel();
     if (_used != null) _used.close();
 
     _discounts = [];