ionic3+anglular4中ngModel如何添加驗證

<input id="myinput" name="myinput" class="form-control"
       required minlength="4" appForbiddenName="bob"
       [(ngModel)]="hero.name" #myinput="ngModel" >

<div *ngIf="myinput.invalid && (myinput.dirty || myinput.touched)" class="alert alert-danger">

  <div *ngIf="myinput.errors.required">
    Name is required.
  </div>
  <div *ngIf="myinput.errors.minlength">
    Name must be at least 4 characters long.
  </div>
  <div *ngIf="myinput.errors.forbiddenName">
    Name cannot be Bob.
  </div>

</div>

required ：不能爲空

minlength：最小長度

appForbiddenName：驗證輸入的字符是否爲bob

#myinput="ngModel"這個最關鍵，#後面的名字跟你的id和name一致