使用angular2形成maxlength字段验证 [英] Form maxlength field validation using angular2

问题描述

如何使用angular2 验证带有maxlength或minlength的用户名字段，而不使用formbuilder 。

How to validate the username field with maxlength or minlength using angular2 without using the formbuilder.

I尝试以下方式，但没有工作

I tried in the following way, but not working

<ion-item>
        <ion-icon name="person" item-left class="placeholder-icon"></ion-icon>
        <ion-label floating primary>Username</ion-label>
        <ion-input [(ngModel)]="login.username" ngControl="username" type="text" #username="ngForm" ng-minlength="5" required>
        </ion-input>
      </ion-item>

      <div [hidden]="username.valid || username.pristine">
        <p *ngIf="username.errors && username.errors.required" danger padding-left>
            user name is required
        </p>
        <p *ngIf="username.errors && username.errors.minlength" danger padding-left>
            min length atleast 5
        </p>
      </div>    
<ion-item>

推荐答案

只需添加 minlength 到你的输入元素。这样， MinLengthValidator 指令将自动添加并注册为验证器：

Simply add the minlength to your input element. This way the MinLengthValidator directive will be automatically added and registered as a validator:

<ion-input [(ngModel)]="login.username"
       ngControl="username" type="text"
       #username="ngForm" minlength="5" required>

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