“等待this.method();"不适用于静态方法 [英] “await this.method();” doesn’t work in static method

问题描述

我知道ES6的 await 功能，我想在类中创建的函数中使用它.

I know of the ES6 await feature and I’d like to use it in a function I created in a class.

它工作正常，但是当该函数是 static 函数时，则不能.有什么理由吗?另外，在 static 函数中使用 await 的正确方法是什么?

It works well, but when the function is a static function, it doesn’t. Is there any reason for that? Also, what will be the right way to be able to use await inside a static function?

class MyClass {
  resolveAfter2Seconds() {
    return new Promise(resolve => {
      setTimeout(() => {
        resolve('resolved');
      }, 2000);
    });
  }

  static async asyncCall() {
    console.log('calling');
    var result = await this.resolveAfter2Seconds();
    console.log(result);
    // expected output: "resolved"
  }
}

MyClass.asyncCall();

推荐答案

您可以在静态函数中正常使用 await .那不是你的问题.

You can use await just fine in a static function. That is not your issue.

但是，静态函数中的 this 是 MyClass ，因此 this.someMethod()正在寻找另一种静态方法，而不是实例方法并且 resolveAfter2Seconds()是一个实例方法，而不是静态方法，因此 this.resolveAfter2Seconds()不会找到该方法，因为这就像调用 MyClass.resolveAfter2Seconds()不存在.

BUT, this in a static function is MyClass so this.someMethod() is looking for another static method, not an instance method and resolveAfter2Seconds() is an instance method, not a static method so this.resolveAfter2Seconds() won't find that method because that's like calling MyClass.resolveAfter2Seconds() which doesn't exist.

如果您还使 resolveAfter2Seconds()成为 static ，则可能会起作用，因为 asyncCall()中的 this code>是 MyClass ，所以 this.resolveAfter2Seconds()正在寻找另一种静态方法.

If you also make resolveAfter2Seconds() be static, then it would probably work because this inside asyncCall() is MyClass so this.resolveAfter2Seconds() is looking for another static method.

这应该在将 resolveAfter2Seconds 设置为静态的情况下起作用:

This should work where you make resolveAfter2Seconds also be static:

class MyClass {

  static resolveAfter2Seconds() {
    return new Promise(resolve => {
      setTimeout(() => {
        resolve('resolved');
      }, 2000);
    });
  }

  static async asyncCall() {
    console.log('calling');
    var result = await this.resolveAfter2Seconds();
    console.log(result);
    // expected output: "resolved"
  }
}

或者，您可以进入原型并从那里调用它，因为它实际上是一个静态方法(根本不引用 this ):

Or, you could reach into the prototype and call it from there because it is actually a static method (doesn't reference this at all):

  static async asyncCall() {
    console.log('calling');
    var result = await MyClass.prototype.resolveAfter2Seconds();
    console.log(result);
    // expected output: "resolved"
  }

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