如何从类中访问元数据注释？ [英] How do I access metadata annotations from a class?

问题描述

我有一个使用元数据注释的Dart类：

I have a Dart class that is annotated with metadata:

class Awesome {
  final String msg;
  const Awesome(this.msg);

  String toString() => msg;
}

@Awesome('it works!')
class Cool {

}

我想看看 Cool 是否注释，如果是，

I want to see if Cool was annotated, and if so, with what. How do I do that?

推荐答案

使用 dart：mirrors 库访问元数据注释。

Use the dart:mirrors library to access metadata annotations.

import 'dart:mirrors';

class Awesome {
  final String msg;
  const Awesome(this.msg);

  String toString() => msg;
}

@Awesome('it works!')
class Cool {

}

void main() {
  ClassMirror classMirror = reflectClass(Cool);
  List<InstanceMirror> metadata = classMirror.metadata;
  var obj = metadata.first.reflectee;
  print(obj); // it works!
}

要了解详情，请参阅ClassMirror#metadata 方法。

To learn more, read about the ClassMirror#metadata method.

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