nilts

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider replacing Future<void> Function() with AsyncCallback, which is defined in the Flutter SDK.

BAD:

final Future<void> Function() callback;

GOOD:

final AsyncCallback callback;

See also:

• AsyncCallback typedef - foundation library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider replacing Future<T> Function() with AsyncValueGetter, which is defined in the Flutter SDK.

BAD:

final Future<int> Function() callback;

GOOD:

final AsyncValueGetter<int> callback;

See also:

• AsyncValueGetter typedef - foundation library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider replacing Future<void> Function(T value) with AsyncValueSetter, which is defined in the Flutter SDK.

BAD:

final Future<void> Function(int value) callback;

GOOD:

final AsyncValueSetter<int> callback;

See also:

• AsyncValueSetter typedef - foundation library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider replacing void Function(T value) with ValueChanged, which is defined in the Flutter SDK. If the value has been set, use ValueSetter instead.

BAD:

final void Function(int value) callback;

GOOD:

final ValueChanged<int> callback;

See also:

• ValueChanged typedef - foundation library - Dart API
• ValueSetter typedef - foundation library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider replacing T Function() with ValueGetter, which is defined in the Flutter SDK.

BAD:

final int Function() callback;

GOOD:

final ValueGetter<int> callback;

See also:

• ValueGetter typedef - foundation library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider replacing void Function(T value) with ValueSetter, which is defined in the Flutter SDK. If the value has changed, use ValueChanged instead.

BAD:

final void Function(int value) callback;

GOOD:

final ValueSetter<int> callback;

See also:

• ValueSetter typedef - foundation library - Dart API
• ValueChanged typedef - foundation library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider replacing void Function() with VoidCallback, which is defined in the Flutter SDK.

BAD:

final void Function() callback;

GOOD:

final VoidCallback callback;

See also:

• VoidCallback typedef - dart:ui library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider using Text.rich or adding the textScaler or textScaleFactor (deprecated in Flutter 3.16.0 and above) argument to the RichText constructor to make the text size responsive to user settings.

BAD:

RichText(
  text: TextSpan(
    text: 'Hello, world!',
  ),
)

GOOD:

Text.rich(
  TextSpan(
    text: 'Hello, world!',
  ),
)

GOOD:

RichText(
  text: TextSpan(
    text: 'Hello, world!',
  ),
  textScaler: MediaQuery.textScalerOf(context),
)

GOOD (deprecated on Flutter 3.16.0 and above):

RichText(
  text: TextSpan(
    text: 'Hello, world!',
  ),
  textScaleFactor: MediaQuery.textScaleFactorOf(context),
)

See also:

• Text.rich constructor - Text - widgets library - Dart API
• RichText class - widgets library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider using the setUp function or performing initialization at the top level or within the test group body. setUpAll may cause flaky tests when tests run concurrently.

BAD:

setUpAll(() {
  // ...
});

GOOD:

setUp(() {
  // ...
});

void main() {
  // do initialization on top level
  // ...

 group('...', () {
  // or do initialization on body of test group
  // ...
 });
}

See also:

• setUpAll function - flutter_test library - Dart API
• setUp function - flutter_test library - Dart API

• Target SDK : >= Dart 3.6.0
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider using digit separators for numeric literals with 5 or more digits to improve readability.

BAD:

const int value = 123456;

GOOD:

const int value = 123_456;

See also:

• Digit Separators in Dart 3.6
• Built-in types | Dart

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider using TextDirection aware configurations if your application supports different TextDirection languages.

BAD:

Align(
  alignment: Alignment.bottomLeft,
)

BAD:

Padding(
  padding: EdgeInsets.only(left: 16, right: 4),
)

BAD:

Positioned(left: 12, child: SizedBox())

GOOD:

Align(
  alignment: AlignmentDirectional.bottomStart,
)

GOOD:

Padding(
  padding: EdgeInsetsDirectional.only(start: 16, end: 4),
)

GOOD:

Positioned.directional(
  start: 12,
  textDirection: TextDirection.ltr,
  child: SizedBox(),
)

PositionedDirectional(
  start: 12,
  child: SizedBox(),
)

See also:

• TextDirection enum - dart:ui library - Dart API
• AlignmentDirectional class - painting library - Dart API
• EdgeInsetsDirectional class - painting library - Dart API
• PositionedDirectional class - widgets library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Prefer using defaultTargetPlatform instead of Platform API if you want to know which platform your application is running on. This is because

• Platform API throws a runtime exception on web application.
• By combining kIsWeb and defaultTargetPlatform, you can accurately determine which platform your web application is running on.

BAD:

bool get isIOS => !kIsWeb && Platform.isIOS;

GOOD:

bool get isIOS => !kIsWeb && defaultTargetPlatform == TargetPlatform.iOS;

See also:

• defaultTargetPlatform property - foundation library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider adding a class modifier (final, sealed, etc.) to explicitly define the inheritance policy of your class.

BAD:

class MyClass {}

GOOD:

final class MyClass {}

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Consider removing the shrinkWrap argument and updating the widget to avoid shrink wrapping. Shrink wrapping the content of a scroll view is significantly more expensive than expanding to the maximum allowed size because the content can expand and contract during scrolling, which means the size of the scroll view needs to be recomputed whenever the scroll position changes.

You can avoid shrink wrapping with the following 3 steps if your scroll view is nested:

1. Replace the parent scroll view with CustomScrollView.
2. Replace the child scroll view with SliverListView or SliverGridView.
3. Set SliverChildBuilderDelegate to delegate argument of the SliverListView or SliverGridView.

BAD:

ListView(shrinkWrap: true)

GOOD:

ListView(shrinkWrap: false)

See also:

• shrinkWrap property - ScrollView class - widgets library - Dart API
• ShrinkWrap vs Slivers | Decoding Flutter - YouTube

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Prefer using MediaQuery.xxxOf or MediaQuery.maybeXxxOf instead of MediaQuery.of or MediaQuery.maybeOf to avoid unnecessary rebuilds.

BAD:

final size = MediaQuery.of(context).size;

GOOD:

final size = MediaQuery.sizeOf(context);

Note that using MediaQuery.of or MediaQuery.maybeOf makes sense in the following cases:

• Wrapping a widget with MediaQuery to override MediaQueryData
• Observing all changes to MediaQueryData

See also:

• MediaQuery as InheritedModel by moffatman · Pull Request #114459 · flutter/flutter
• MediaQuery class - widgets library - Dart API

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ✅

Prefer using the if-null operator, null-aware operator, or pattern matching instead of force type casting with the ! operator.

BAD:

final value = someValue!;

GOOD:

final value = someValue ?? /* default value */;

GOOD:

final value = someValue?.someMethod();

See also:

• Operators | Dart
• Patterns | Dart

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ❌

Consider using a more stable way to handle enum values. The name property is a string representation of the enum value, which can be changed without breaking the code.

BAD:

void printColorValue(Color color) {
  print(color.name); // 'red', 'green', 'blue'
}

GOOD:

enum Color {
  red,
  green,
  blue,
  ;

  String get id => switch (this) {
    red => 'red',
    green => 'green',
    blue => 'blue',
  };
}

void printColorValue(Color color) {
  print(color.id);
}

See also:

• Enums | Dart

• Target SDK : Any versions nilts supports
• Rule type : Practice
• Maturity level : Stable
• Severity : Info
• Quick fix : ❌

Consider using a more stable way to handle enum values. The values property returns a mutable List, which can be modified and may cause unexpected behavior.

BAD:

enum Color { red, green, blue }

void printColors() {
  for (final color in Color.values) {
    print(color);
  }
}

GOOD:

enum Color { red, green, blue }

void printColors() {
  final colors = [Color.red, Color.green, Color.blue];
  for (final color in colors) {
    print(color);
  }
}

See also:

• Enums - Dart language specification