One solution is to use a function to set the value. This gives you more options. A function that isn’t provided: null This will not change the value A function that is provided and returns null: () => null This will set the value to null A function that returns the name: () => ‘Gustavo’ … Read more
When assigning the Mock object, it needs to be of the Mock object type, not the BaseClass. @GenerateMocks(MockSpec<ITransactionRepository>(as: #MockTransactionRepository), ) void main() { …. ITransactionRepository baseObject = MockTransactionRepository(); // wrong MockTransactionRepository mockObject = MockTransactionRepository(); // right when(baseObject.method(any)); // results in compile error when(mockObject.method(any)); // OK … } Source: https://github.com/dart-lang/mockito/issues/364
Use dart pub outdated –mode=null-safety and then dart pub upgrade –null-safety to upgrade all your dependencies to null-safety. For more details go to https://dart.dev/null-safety/migration-guide.
Change your code to accept a VoidCallback instead of Function for the onPressed. By the way VoidCallback is just shorthand for void Function() so you could also define it as final void Function() onPressed; Updated code: class DrawerItem extends StatelessWidget { final String text; final VoidCallback onPressed; const DrawerItem({Key key, this.text, this.onPressed}) : super(key: key); … Read more
I found out that json_serializable >=4.0.0 depends on json_annotation >=4.0.0 <4.1.0 and the json_annotation: ^4.0.0 includes Null Safety but json_serializable: ^4.0.2 does not, so the error is occurring. So I downgraded both packages: json_annotation: 3.1.1 and json_serializable: 3.5.1 And they work again properly.
Null safety is no longer an experiment as of Dart 2.12. It is now easy to enable. Enabling null safety Starting with the first Dart 2.12 versions, types will be non-nullable by default. So you just need to change your SDK constraint: environment: sdk: “>=2.12.0 <3.0.0″ Learn more about “Enabling null safety” on dart.dev.
Short answer: Instead of the pre-null-safety operations var foo = List<int>(); // Now error var bar = List<int>(n); // Now error var baz = List<int>(0); // Now error use the following: var foo = <int>[]; // Always the recommended way. var bar = List.filled(1, 0); // Not filled with `null`s. var baz = List<int>.empty(); Long … Read more
(Your code was fine before Dart 2.12, null safety) With null safety, Dart doesn’t know if you actually assigned a value to count. Dart initializes objects in two phases, and Dart expects all member variables to already be initialized when the constructor’s body executes. Because your members are non-nullable and haven’t been initialized to non-null … Read more
1. Null safety / non-nullable (by default) The null safety / non-nullable (by default), short NNBD, feature can currently be found at nullsafety.dartpad.dev. Keep in mind that you can read the full spec here and full roadmap here. Now, sound null safety has also been officially announced for Dart. 2.1. What does non-nullable by default … Read more
Why The reason this happens is because with null safety enabled, your non-nullable parameter factor or key cannot be null. In the function and the constructor, these values might be null when the function is called without the named parameter: calculate() or Foo(). However because the types (int and Key) are non-nullable, this is invalid … Read more