fix errors

lib/pages/discount/discount_list_row.dart

@@ -8,9 +8,12 @@ import 'package:flutter/material.dart';
 import 'package:flutter_icons/flutter_icons.dart';
 import 'package:intl/intl.dart';
 
+typedef OnSelect(Discount discount);
+
 class DiscountListRow extends StatelessWidget {
+  final OnSelect onSelect;
   final Discount discount;
-  DiscountListRow({Key key, this.discount}) : super(key: key);
+  DiscountListRow({Key key, this.discount, this.onSelect}) : super(key: key);
 
   final DateFormat dateFormat = new DateFormat("dd MMM yyyy");
 
@@ -18,11 +21,9 @@ class DiscountListRow extends StatelessWidget {
   Widget build(BuildContext context) {
     return InkWell(
       onTap: () {
-        Navigator.push(
-          context,
-          CupertinoPageRoute(
-              builder: (context) => DiscountEditor(discount: discount)),
-        );
+        if (onSelect != null) {
+          onSelect(discount);
+        }
       },
       child: Container(
         padding: EdgeInsets.only(left: 15, right: 15),