how to show validate message in form in angular 2?

Question

I am trying to show validate message in form in angular 2 ? I am getting this error

Cannot read property \'hasError\' of undefined

I added these

Answer 1

This should do what you want:

<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