选择域角度2的验证 [英] Validation for select field angular 2

问题描述

我正在使用 angular2@2.4.1 版本.我将如何对选择的 field 字段进行 validation ?

I am using angular2@2.4.1 release. How would i do a validation on select field?

<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>

基本上我想在选择字段无效时禁用该按钮吗?当未选择任何值时，如何使选择字段无效?

Basically i want to disable the button when the select field is invalid? How do i make the select field invalid when no value is selected?

推荐答案

您可以创建一个布尔变量并将其分配为默认值 false .当用户选择任何选项时，它将变为true.

You can make a boolean variable and assign to it false as default value. When user chooses any option, it will turn true.

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;

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