javascript - 选择视场 Angular 2 的验证

Question

我正在使用 angular2@2.4.1 版本。我将如何对选择的字段进行验证？

<div class="form-group" [class.has-error] = "schoolError">
            <label class="control-label" for="lang">Select School</label>
            <select class="form-control" name="school"  
            required #school
            [(ngModel)] = "model.school">
                <option value="default">Select a school</option>
                <option *ngFor= "let sch of school">{{sch}}</option>
            </select>
        </div>   

 <button class="btn btn-primary" 
     [disabled] = "form.invalid" type="submit">Submit</button>

基本上我想在 select field 无效时禁用按钮？未选择任何值时如何使选择字段无效？

Answer 1

您可以创建一个 bool 变量并将 false 作为默认值分配给它。当用户选择任何选项时，它将变为真。

https://plnkr.co/edit/yR5xz4h3llkxHsUQxFJB?p=preview

<div>
  <select [(ngModel)]='selected'>
    <option value='one'>Three</option>
    <option value='two'>Two</option>
  </select>
  <button [disabled]='!selected && form.status == 'VALID'>click</button>
</div>

selected:boolean = false;