Flutter upgrade

lib/core/validator.dart

@@ -1,13 +1,13 @@
 import 'package:flutter/foundation.dart';
 
 abstract class Validator<T> {
-  Validator({@required this.errorMessage});
+  Validator({required this.errorMessage});
 
   final String errorMessage;
 
-  bool isValid(T value);
+  bool isValid(T? value);
 
-  String call(T value) => !isValid(value) ? errorMessage : null;
+  String? call(T? value) =>  !isValid(value) ? errorMessage : null;
 }
 
 class TextValidator extends Validator<String> {
@@ -15,28 +15,28 @@ class TextValidator extends Validator<String> {
       {this.minLength,
       this.maxLength,
       this.pattern,
+      String errorMessage = '',
       this.length,
-      this.isAutovalidate = false,
-      String errorMessage})
+      this.isAutovalidate = false})
       : super(errorMessage: errorMessage);
 
-  final int minLength;
-  final int maxLength;
-  final List<int> length;
+  final int? minLength;
+  final int? maxLength;
+  final List<int>? length;
   final bool isAutovalidate;
-  String pattern;
+  String? pattern;
 
   @override
-  bool isValid(String value) {
+  bool isValid(String? value) {
     if (value == null || value.isEmpty) {
       return isAutovalidate ? true : false;
     }
 
     return value.length > (minLength ?? 0) &&
         (length?.contains(value.length) ?? true) &&
-        ((maxLength ?? 0) > 0 ? (value.length <= maxLength) : true) &&
+        ((maxLength ?? 0) > 0 ? (value.length <= maxLength!) : true) &&
         (pattern != null ? match(value) : true);
   }
 
-  bool match(String value) => RegExp(pattern).hasMatch(value);
+  bool match(String value) => pattern != null ? RegExp(pattern!).hasMatch(value) : false;
 }