如何在ngSwitchCase

Question

我发现了多个帖子，包括ngSwitchCase in angular 2 instead of ngSwitchWhen，How to bind to '*ngSwitchCase'和Angular 2 - ngSwitchCase。 Google根本没有帮助。

我正在尝试创建一个用于输入搜索条件的简单表格。第一个组件是选择框，第二个组件是输入框。根据您要进行的搜索类型，我想对电子邮件，电话号码等使用不同的输入。

我正在从表单中定义的常量中选择内容。

const SEARCH_BY_EMAIL = 'email';
const SEARCH_BY_PHONE = 'phone';
const SEARCH_BY_POSTAL_CODE = 'postalCode';

@Component({
  selector: 'app-choose-search-criteria',
  templateUrl: './choose-search-criteria.component.html',
  styleUrls: ['./choose-search-criteria.component.css']
})
export class ChooseSearchCriteriaComponent implements OnInit {

  searchTypes = [
      {value: SEARCH_BY_EMAIL, label: 'Email'},
      {value: SEARCH_BY_PHONE, label: 'Phone Number'},
      {value: SEARCH_BY_POSTAL_CODE, label: 'Zip Code'}
    ];
  searchBy: string;
  searchValue = '';

  constructor(protected dialogRef: MatDialogRef<ChooseSearchCriteriaComponent>,
              @Inject(MAT_DIALOG_DATA) public data: ChooseCriteriaDialogData) { }

  ngOnInit() {
  }

}

<h2>Enter Search Values</h2>
<div class="formFields">
  <mat-form-field>
    <mat-label>Search By</mat-label>
    <mat-select [(value)]="searchBy">
      <mat-option *ngFor="let searchType of searchTypes" [value]="searchType.value">
        {{searchType.label}}
      </mat-option>
    </mat-select>
  </mat-form-field>
  <div [ngSwitch]="searchBy">
    <mat-form-field *ngSwitchCase="SEARCH_BY_EMAIL">
      <input matInput placeholder="Enter Email Address" type="email" [(ngModel)]="searchValue"/>
    </mat-form-field>
    <mat-form-field *ngSwitchCase="SEARCH_BY_PHONE">
      <input matInput placeholder="Enter Phone Number" type="number" [(ngModel)]="searchValue"/>
    </mat-form-field>
    <mat-form-field *ngSwitchCase="SEARCH_BY_POSTAL_CODE">
      <input matInput placeholder="Enter Zip Code" type="number" [(ngModel)]="searchValue"/>
    </mat-form-field>

    <p *ngSwitchDefault>Select how you wish to search.</p>
  </div>
</div>

问题在于，似乎在ngSwitchCase上找不到我的常量。我也尝试过{SEARCH_BY_POSTAL_CODE}和{{SEARCH_BY_POSTAL_CODE}}，但它们似乎也不起作用。

所以，我被困住了。请咨询？

Answer 1

在组件类内部将常量移动为readonly字段。

在模板中，您只能引用组件类的属性和方法。