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如何定义泛型函数的typedef?

dart-2 dart

3

arielnmz · 技术社区 · 7 年前

我有一个像这样的通用静态方法:

static build<K>() {
    return (GenericClass<K> param) => MyClass<K>(param);
}

typedef F = MyClass<K> Function(GenericClass<K> param);

The return type '(GenericClass<K>) â MyClass<K>' isn't a '(GenericClass<dynamic>) â MyClass<dynamic>', as defined by the method 'build'.

typedef F = SimpleViewModel<K> Function<k>(Store<K> param);

The return type '(GenericClass<K>) â MyClass<K>' isn't a '<K>(GenericClass<K>) â MyClass<K>', as defined by the method 'build'.

MyClass

class MyClass<T> {
  final GenericClass<T> param;

  MyClass(this.param);


  static build<K>() {
      return (GenericClass<K> param) => MyClass<K>(param);
  }
}

typedef

1 回复 | 直到 7 年前

1

4

Nate Bosch 7 年前

T 以下内容:

typedef F<T> = T Function(T);

F first = (dynamic arg) => arg; // F means F<dynamic>
F<String> second = (String arg) => arg; // F<String> means both T must be String

M

typedef F = M Function<M>(M);

然后在使用中:

F first = <M>(M arg) => arg; // The anonymous function is defined as generic
// F<String> -> Illegal, F has no generic argument
// F second = (String arg) => arg -> Illegal, the anonymous function is not generic

typedef F<T> = M Function<M>(T,M);

F first = <M>(dynamic arg1, M arg2) => arg2; // F means F<dynamic> so the T must be dynamic
F<String second = <M>(String arg1, M arg2) => arg2; // The T must be String, the function must still be generic on the second arg and return type