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限制方法修饰符的使用

decorator generics typescript

lilezek · 技术社区 · 7 年前

class A {
  @deco() // This should work.
  public async works() { }
  @deco() // This should fail.
  public fails() { }
}

我试图这样定义装饰师:

export function deco() {
  return <T extends {[K in keyof T]: () => Promise<any>}, 
          K extends string>
         (target: T, 
          propertyKey: K, 
          descriptor: PropertyDescriptor) => {
    // Decorator code here.
  };
}

但它不起作用。这两个方面都失败了 works 和 fails K [K in keyof T] 和 K K extends string 和 propertyKey: K K 不限于T的键。

这也不起作用:

export function deco() {
  return <T extends {[K in keyof T]: () => Promise<any>}, 
          K extends keyof T>
         (target: T, 
          propertyKey: K, 
          descriptor: PropertyDescriptor) => {
    // Decorator code here.
  };
}

这两者都不是:

export function deco() {
  return <T, 
          K extends keyof T>
         (target: T & {[propertyKey]: () => Promise<any>}, 
          propertyKey: K, 
          descriptor: PropertyDescriptor) => {
    // Decorator code here.
  };
}

知道吗?

1 回复 | 直到 7 年前

Titian Cernicova-Dragomir 7 年前

您应该使用方法装饰器,而不是属性装饰器:

declare type MethodDecorator = <T>(target: Object, propertyKey: string | symbol, descriptor: TypedPropertyDescriptor<T>) => TypedPropertyDescriptor<T> | void;

function TypeRestrictedMethodDecorator(
    target: Object, // The prototype of the class
    propertyKey: string, // The name of the method
    descriptor: TypedPropertyDescriptor<(... p:any[]) => Promise<any>>
    ) {
    console.log("TypeRestrictedMethodDecorator called on: ", target, propertyKey, descriptor);
}

class TypeRestrictedMethodDecoratorExample {
    @TypeRestrictedMethodDecorator
    method(num: number): Promise<number> {
        return new Promise((res, rej)=> res(10));
    }

    @TypeRestrictedMethodDecorator // Error
    method2(num: number): number {
        return 10;
    }
}

样本修改自 here