dart - 如何在 Dart 的类中动态创建方法或 setter？

Question

是否可以从此类内部或外部向现有类动态添加实例方法或 setter？

Answer 1

不，您不能向类(class)添加真正的成员。

我说真正的成员是因为你可以用noSuchMethod()模拟这样的特征.这里有一个例子:

@proxy
class A {
  final dynamicMethods = <Symbol, Function>{};

  noSuchMethod(Invocation i) {
    if (i.isMethod && dynamicMethods.containsKey(i.memberName)) {
      return Function.apply(dynamicMethods[i.memberName],
          i.positionalArguments, i.namedArguments);
    }
    return super.noSuchMethod(i);
  }
}

main() {
  final a = new A();
  a.dynamicMethods[#sayHello] = () => print('hello');
  a.sayHello();
}

在未来这也许是可能的。请参阅 the article on Mirrors 中的这段摘录:

We’d like to support more powerful reflective features in the future. These would include mirror builders, designed to allow programs to extend and modify themselves, and a mirror-based debugging API as well.