如何验证和显示错误消息 - Angular 2 Material 设计?

How to Validate & Display Error Message - Angular2 Material Design?

我有这个输入:

<form #f="ngForm" name="productForm">
     <md-input [(ngModel)]="product.price" name="price" required="true" placeholder="Price (USD)"></md-input>
     <div ng-messages="productForm.price.$error" role="alert">
         <div ng-message-exp="['required']">
              Price is required
          </div>
     </div>
</form>

但是没有显示需要价格的消息。

我应该如何正确设置错误消息的格式?

输入价格为空时出现ng-invalid class:

当我填写一些东西时:

Angular 在其中注入 ng-valid class 。

我想要的是类似于angular1 md design的样式,看起来像这样:

希望这将随着 angular2-material 的发展而添加,但目前模仿它的方法是设置 dividerColor 并使用 MD-HINT 指令。示例:

<md-input placeholder="Email address"
    #email="ngModel"
    name="email"
    type="text"
    fullWidth={true}
    [(ngModel)]="model.email"
    required
    email
    dividerColor="{{ !email.valid ? 'warn' : 'primary' }}">
    <md-hint [hidden]="email.pristine || email.valid">
        <span [hidden]="email.errors?.required || !email.errors?.email">
            This doesn't appear to be a valid email address.
        </span>
        <span [hidden]="!email.errors?.required">Email address is required.</span>
    </md-hint>
</md-input>

现在可以使用 Angular Material 版本 2.0.0 插入验证消息。查看文档 here.

<form class="example-form">
  <mat-form-field class="example-full-width">
    <input matInput placeholder="Email" [formControl]="emailFormControl">
    <mat-error *ngIf="emailFormControl.hasError('pattern')">
      Please enter a valid email address
    </mat-error>
    <mat-error *ngIf="emailFormControl.hasError('required')">
      Email is <strong>required</strong>
    </mat-error>
  </mat-form-field>
</form>

在全局输入时显示mat-error:

1- 导入库:

import { ErrorStateMatcher, ShowOnDirtyErrorStateMatcher } from '@angular/material/core'; 

2- 添加到提供商,如:

@NgModule({
  providers: [
    AuthService,
    UserService,
    { provide: ErrorStateMatcher, useClass: ShowOnDirtyErrorStateMatcher }
  ],
})

3- 重新提供应用程序。