What is deprecated how to use it with methods in flutter with sample code ?

@deprecated Annotation in Flutter

@deprecated marks APIs as no longer recommended. It warns developers to use alternatives.

Basic Usage

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import 'package:meta/meta.dart';

@deprecated('Use newFunction() instead')
void oldFunction() {
  print('This is deprecated');
}

void newFunction() {
  print('Use this instead');
}

void main() {
  oldFunction(); // Warning: "deprecated"
  newFunction(); // OK
}

Deprecating Methods

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class User {
  String name = 'Alice';

  @deprecated('Use printName() instead')
  void displayName() {
    print(name);
  }

  void printName() {
    print(name);
  }
}

Deprecating Classes

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@deprecated('Use NewUserWidget instead')
class OldUserWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text('Old');
  }
}

class NewUserWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Text('New');
  }
}

Deprecating Constructors

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class Config {
  String apiUrl;

  @deprecated('Use Config.fromEnv() instead')
  Config(this.apiUrl);

  Config.fromEnv() : apiUrl = String.fromEnvironment('API_URL');
}

Best Practice: Provide migration path in message.