如何在角度 2 中显示危险的错误消息

Question

已将表单创建为 First_Name 和 Last_Name.. Angular 2 中是否有任何通用表单验证器，并且我已经在客户端显示了错误消息。如何显示处于危险之中！！

下面是我的代码

html文件

<form [formGroup]="myForm"  (ngSubmit)="submit()" >

<ion-item>
  <ion-label primary floating>FIRST NAME</ion-label>
  <ion-input type="text" id="firstname" class="form-control" formControlName="firstname" minlength="4" maxlength="12" required ></ion-input>
</ion-item>  
  <p *ngIf="myForm.controls.firstname.errors && myForm.controls.firstname.dirty " danger > FirstName is required (b/w 4-12 chars)</p>
<ion-item>
  <ion-label primary floating>LAST NAME</ion-label>
  <ion-input type="text" id="lastname" class="form-control" formControlName="lastname" minlength="4" maxlength="10" required ></ion-input>
</ion-item>
  <p *ngIf="myForm.controls.lastname.errors && myForm.controls.lastname.dirty " danger> LastName is required (b/w 1-10 chars)</p>
</form>

告诉我如何在危险中显示错误信息！

Answer 1

     <form role="form" name="myForm" novalidate="">
       <div data-ng-show="myForm.controls.firstname.errors && myForm.controls.firstname.dirty" class="alert alert-danger alert-   dismissible" role="alert">
                <strong>FirstName is required (b/w 4-12 chars)</strong> 
            </div>

            <div data-ng-show="myForm.controls.lastname.errors && myForm.controls.lastname.dirty" class="alert alert-danger alert-dismissible" role="alert">
                <strong>LastName is required (b/w 1-10 chars)</strong> 
            </div>
    </form>