什么时候调用Angular2自定义验证程序指令？

Question

我按照以下博客创建了自定义验证程序指令。 http://blog.thoughtram.io/angular/2016/03/14/custom-validators-in-angular-2.html

通过Chrome调试器，我看到EmailValidator构造函数被调用，但是在我输入或当字段失去焦点时，从未调用validate（）方法。

从以下博客提供代码。我注释掉了对EmailBlackList的引用。

<form novalidate>
  ...
  <input type="email" name="email" ngModel validateEmail>
</form>


import {Directive, forwardRef} from '@angular/core';
import {NG_VALIDATORS, FormControl} from '@angular/forms';

function validateEmailFactory(/*emailBlackList: EmailBlackList*/) {
  return (c: FormControl) => {
    let EMAIL_REGEXP = /^[a-z0-9!#$%&'*+\/=?^_`{|}~.-]+@[a-z0-9]([a-z0-9-]*[a-z0-9])?(\.[a-z0-9]([a-z0-9-]*[a-z0-9])?)*$/i;

    return EMAIL_REGEXP.test(c.value) ? null : {
      validateEmail: {
        valid: false
      }
    };
  };
}

@Directive({
  selector: '[validateEmail][ngModel],[validateEmail][formControl]',
  providers: [
    { provide: NG_VALIDATORS, useExisting: forwardRef(() => EmailValidator), multi: true }
  ]
})
export class EmailValidator {

  validator: Function;

  constructor(/*emailBlackList: EmailBlackList*/) {
    this.validator = validateEmailFactory(/*emailBlackList*/);
  }

  validate(c: FormControl) {
    return this.validator(c);
  }
}