Angular2 - 依赖于并行调用的AsyncValidator

Question

我遇到了AsyncValidators的问题。通常，解决的承诺取决于promise本身调用的代码，但是从外部调用代码并且promise必须监听它时呢？我不确定我是否正确解释了这一点，但这是一个例子：

public valid: boolean;

ngOnInit() {
  ...
  formControl = new FormControl('', this.asyncValidator.bind(this))
}

/* some code runs an external request and runs setValid() */

setValid(valid: boolean) {
  this.valid = valid;
  ...
}

asyncValidator(): { [key: string]: any } {
  ...
  return new Promise(resolve => {
    /* somehow waiting on the setValid() function to be run */
  });
}

我确实尝试过这种方法：

public valid: boolean;

ngOnInit() {
  ...
  formControl = new FormControl('', this.asyncValidator.bind(this))
}

/* some code runs an external request and runs setValid() */

setValid(valid: boolean) {
  if (this.callDone) {
    if (valid) {
      this.callDone(null);
    }
    else {
      this.callDone({ 'wrong': true });
    }
  }
  this.callDone = null;
  this.valid = valid;
}

asyncValidator(): { [key: string]: any } {
  if (this.callDone)
    this.callDone(this.valid);
  return new Promise(resolve => {
    this.callDone = resolve;
  });
}

但这不会改变形式的状态。 callDone（）似乎已经解决，但它仍然无法正常工作。我可能做错了什么？