打字稿 + ES6 代理

Question

ES6 Proxy.apply 方法提供了一种使用没有“new”关键字的类的方法。

但在 TypeScript 上，它会给出错误“'typeof ClassName' 类型的值不可调用。您的意思是包含 'new' 吗？”。

有什么方法可以防止 TypeScript 错误？

这是一个简单的例子；

class ClassName {
  constructor(anyThing?: any) {
    if (anyThing) {
      // Do something
    }
  }
}

// ES6 Proxy
const CustomName = new Proxy(ClassName, {
  apply: (Target, _thisArg, argumentsList) => {
    return new Target(...argumentsList);
  }
});

// Test ---------
new ClassName("test"); // return ClassName { }

// No error
new CustomName("test"); // return ClassName { }

// Javascript: no error
// TypeScript: error => Value of type 'typeof ClassName' is not callable. Did you mean to include 'new'?
CustomName("test"); // return ClassName { }

Answer 1

使用 Target 的静态方法使 Proxy 可调用

class ClassName {
  constructor(anyThing?: any) {
    if (anyThing) {
      // Do something
    }
  }

  // Forge
  static forge (anyThing?: any) {
    return new ClassName(anyThing);
  }
}

// ES6 Proxy
const CustomName = new Proxy(ClassName, {
  apply: (Target, _thisArg, argumentsList) => {
    return new Target(...argumentsList);
  }
}) as typeof ClassName & typeof ClassName.forge;

let instance: ClassName;

instance = new ClassName();
instance = new CustomName();
instance = CustomName();

Answer 2

Typescript 无法理解您的 apply 函数对类的作用。您将需要扩充类型。

解决方案 (playground)

class ClassName {
  constructor(anyThing?: any) {
    if (anyThing) {
      // Do something
    }
  }
}

// ES6 Proxy
const CustomName = new Proxy(ClassName, {
  apply: (Target, _thisArg, argumentsList) => {
    return new Target(...argumentsList);
  },
  get: () => { ... }, // Implement static method(s)
}) as typeof ClassName & (() => ClassName) & { staticMethod(): CustomName };

let instance: ClassName;

instance = new ClassName();
instance = new CustomName();
instance = CustomName();
instance = CustomName.staticMethod();