如何以角度2显示表单中的验证消息？

Question

我正在尝试以角度2显示表单中的验证消息？我收到此错误

无法读取未定义的属性'hasError'

我添加了这些行

 <div *ngIf="username.hasError('required') && username.touched" 
           class="error-box"> username is required</div>    
       <div *ngIf="username.hasError('minlength') && username.touched" 
           class="error-box"> Minimum password length is 8!</div>

这是我的代码 https://plnkr.co/edit/slhySWT0mJXkloGK1kfO?p=preview

Answer 1

这应该做你想要的：

<ion-input type="text" ngControl="username" #username="ngForm"></ion-input>

 <div *ngIf="username.errors?.required && username.touched" 
           class="error-box"> username is required</div>    
       <div *ngIf="username.errors?.minlength && username.touched" 
           class="error-box"> Minimum password length is 8!</div>

Plunker example