Metadata
Use metadata to give additional information about your code. A metadata annotation begins with the character @, followed by either a reference to a compile-time constant (such as deprecated ) or a call to a constant constructor.
Two annotations are available to all Dart code: @deprecated and @override. For examples of using @override, see Extending a class. Here’s an example of using the @deprecated annotation:
class Television {
/// _Deprecated: Use [turnOn] instead._
@deprecated
void activate() {
turnOn();
}
/// Turns the TV's power on.
void turnOn() {...}
}
You can define your own metadata annotations. Here’s an example of defining a @todo annotation that takes two arguments:
library todo;
class Todo {
final String who;
final String what;
const Todo(this.who, this.what);
}
And here’s an example of using that @todo annotation:
import 'todo.dart';
@Todo('seth', 'make this do something')
void doSomething() {
print('do something');
}
Metadata can appear before a library, class, typedef, type parameter, constructor, factory, function, field, parameter, or variable declaration and before an import or export directive. You can retrieve metadata at runtime using reflection.