如何應用所需的驗證下拉角2

Question

我正在使用選擇html標記，我是綁定列表。如果未選擇下拉菜單並在其標題上顯示「選擇」，我需要進行必要的驗證。

Answer 1

<div [hidden]="power.valid " class="alert alert-danger" style="padding: 0px;margin-bottom: 2px;"> 
      Select 
     </div> 
     <select class="form-control" required 
      ngControl="power" #power="ngForm" > 
      <option *ngFor="let p of powers" [value]="p">{{p}}</option> 
     </select> 

在這裏實現：http://plnkr.co/edit/LlnAOSqWMmnolONbZNhf?p=preview

Answer 2

我用*ngIf語法，但你可以像下拉菜單提供驗證：

<div class="form-group"> 
    <div> 
     <label for="country">Country*:</label> 
    </div> 
    <div ng-class="{'valid':country.$valid}"> 
     <select class="form-control" name='country' [(ngModel)]='fd.country' required> 
      <option *ngFor="let obj of country" [ngValue]="obj">{{obj}}</option> 
     </select> 
    </div> 
    <small *ngIf="(myForm._submitted && !country.valid && !fd.country) || (!country.valid && country.dirty) ">Required (Please select country).</small> 
</div>