react表单上的自定义验证器用于密码并确认密码匹配将未定义的参数导入 Angular 4

我正在try 实现一个自定义验证器，以判断密码和密码确认是否相等.问题是验证器正在获取未定义的密码和confirmedPassword参数.我该怎么做.如果我将条件改为===而不是！==当字段相同时，它会正确抛出错误.有人知道这里的错误是什么吗？

signup.component.html

<div class="col-md-7 col-md-offset-1 col-sm-7">
  <div class="block">
    <div class="well">
        <form (onSubmit)="onSubmit()" [formGroup]="signUpForm">
          <div class="form-group">
            <label for="username" class="control-label">Nombre de usuario:</label>
            <input type="text" class="form-control" formControlName="username"  title="Please enter your username" placeholder="username">
            <p class="help-block" *ngIf="signUpForm.get('username').hasError('required') && signUpForm.get('username').touched">El nombre de usuario es obligatorio</p>
            <p class="help-block" *ngIf="signUpForm.get('username').hasError('minlength') && signUpForm.get('username').touched">El nombre de usuario debe tener al menos 6 caracteres</p>
            <p class="help-block" *ngIf="signUpForm.get('username').hasError('maxlength') && signUpForm.get('username').touched">El nombre de usuario debe tener menos de 15 caracteres</p>
          </div>
          <div class="form-group">
            <label for="email" class="control-label">E-mail:</label>
            <input class="form-control" formControlName="email" title="Please enter your email" placeholder="example@gmail.com">
            <p class="help-block" *ngIf="signUpForm.get('email').hasError('required') && signUpForm.get('email').touched">La dirección de email es obligatoria</p>
            <p class="help-block" *ngIf="signUpForm.get('email').hasError('email') && signUpForm.get('email').touched">Debe ingresar una dirección de correo válida</p>
          </div>
          <div class="form-group">
            <label for="password" class="control-label">Contraseña:</label>
            <input type="password" class="form-control" formControlName="password" title="Please enter your password" [(ngModel)]="password">
            <p class="help-block" *ngIf="signUpForm.get('password').hasError('required') && signUpForm.get('password').touched">Debe ingresar una contraseña</p>
          </div>
          <div class="form-group">
            <label for="confirmedPassword" class="control-label">Confirmar Contraseña:</label>
            <input type="password" class="form-control" formControlName="confirmedPassword"  title="Please re-enter your password" [(ngModel)]="confirmedPassword">
            <p class="help-block" *ngIf="signUpForm.get('confirmedPassword').hasError('required') && signUpForm.get('confirmedPassword').touched">La confirmación de contraseña no puede estar vacía</p>
            <p class="help-block" *ngIf="signUpForm.get('confirmedPassword').hasError('passwordMismatch') && signUpForm.get('confirmedPassword').touched">Las contraseñas no coinciden</p>
          </div>
          <button type="submit" class="btn btn-success" [disabled]="!signUpForm.valid">Registrarse</button>
          <a routerLink="/signin" class="btn btn-default" style="">Ya tenes usuario? Logueate</a> {{ creationMessage }}
        </form>

      </div>

  </div>
</div>

signup.component.ts

import { Component, OnInit, ViewChild, Input } from '@angular/core';
import { FormControl, FormGroup, Validators } from '@angular/forms';
import { CustomValidators } from '../../shared/custom-validators';
import { Observable } from 'rxjs/Observable';

@Component({
  selector: 'app-signup',
  templateUrl: './signup.component.html',
  styleUrls: ['./signup.component.sass']
})
export class SignupComponent implements OnInit {

  signUpForm: FormGroup;
  user = {
    username: '',
    email: '',
    password: ''
  };
  submitted = false;
  @Input() password='';
  @Input() confirmedPassword='';

  constructor() { }

  ngOnInit() {

    this.signUpForm = new FormGroup({
      'username': new FormControl(null, [Validators.required, Validators.minLength(6), Validators.maxLength(15)]),
      'email': new FormControl(null, [Validators.required, Validators.email, Validators.minLength(5)]),
      'password': new FormControl(null, [Validators.required]),
      'confirmedPassword': new FormControl(null, [Validators.required, CustomValidators.passwordsMatch(this.password,this.confirmedPassword).bind(this)])
    });
  }

  onSubmit() {
    if (this.signUpForm.valid) {
      console.log(this.signUpForm.value);
    }
  }

}

custom-validators.ts

    import { FormControl } from '@angular/forms';

    export class CustomValidators{

    public static passwordsMatch(password: string, confirmedPassword: string) {

     return (control: FormControl) : { [s: string]: boolean } =>{
       //getting undefined values for both variables
       console.log(password,confirmedPassword);
        //if I change this condition to === it throws the error if the 
//  two fields are the same, so this part works
        if (password !== confirmedPassword) {
          return { 'passwordMismatch': true }
        } else {
          //it always gets here no matter what
          return null;
        }
    }
      }


    }