Typescript枚举看起来和Angular2的ngSwitch指令很匹配。但是当我试图在我的组件的模板中使用枚举时,我得到“无法读取属性'xxx'的未定义在…”如何在组件模板中使用枚举值?

请注意,这与如何基于枚举(ngFor)的所有值创建html选择选项不同。这个问题是关于基于枚举的特定值的ngSwitch。尽管出现了创建枚举的类内部引用的相同方法。


当前回答

你现在可以这样做:

例如,枚举为:

export enum MessagePriority {
    REGULAR= 1,
    WARNING,
    IMPORTANT,
}

一个状态消息,看起来像这样:

export default class StatusMessage{
    message: string;
    priority: MessagePriority;

    constructor(message: string, priority: MessagePriority){
        this.message = message;
        this.priority = priority;
    }
}

然后在组件的.ts文件中,你可以这样做:

    import StatusMessage from '../../src/entities/building/ranch/administration/statusMessage';
    import { MessagePriority } from '../../enums/message-priority';
            
    export class InfoCardComponent implements OnInit {
     messagePriority: typeof MessagePriority;
                
     constructor() { 
     this.messagePriority = MessagePriority;
    }
                
    @Input() statusMessage: StatusMessage;
    ngOnInit(): void {}
}

最后这个组件的HTML是这样的:

<div class="info-card" [ngSwitch]="statusMessage.priority">
    <h2 *ngSwitchCase="this.messagePriority.REGULAR" class="info-card__regular-message">{{statusMessage.message}}</h2>
    <h2 *ngSwitchCase="this.messagePriority.WARNING" class="info-card__warning-message">{{statusMessage.message}}</h2>
    <h2 *ngSwitchCase="this.messagePriority.IMPORTANT" class="info-card__important-message">{{statusMessage.message}}</h2>
</div>

注意,枚举首先用“typeof messagpriority”类型声明给类,然后用“this”调用定义来绑定到类。messagpriority = messagpriority "

其他回答

你可以在你的组件类中创建一个对枚举的引用(我只是将初始字符改为小写),然后从模板(plunker)中使用该引用:

import {Component} from 'angular2/core';

enum CellType {Text, Placeholder}
class Cell {
  constructor(public text: string, public type: CellType) {}
}
@Component({
  selector: 'my-app',
  template: `
    <div [ngSwitch]="cell.type">
      <div *ngSwitchCase="cellType.Text">
        {{cell.text}}
      </div>
      <div *ngSwitchCase="cellType.Placeholder">
        Placeholder
      </div>
    </div>
    <button (click)="setType(cellType.Text)">Text</button>
    <button (click)="setType(cellType.Placeholder)">Placeholder</button>
  `,
})
export default class AppComponent {

  // Store a reference to the enum
  cellType = CellType;
  public cell: Cell;

  constructor() {
    this.cell = new Cell("Hello", CellType.Text)
  }

  setType(type: CellType) {
    this.cell.type = type;
  }
}

你现在可以这样做:

例如,枚举为:

export enum MessagePriority {
    REGULAR= 1,
    WARNING,
    IMPORTANT,
}

一个状态消息,看起来像这样:

export default class StatusMessage{
    message: string;
    priority: MessagePriority;

    constructor(message: string, priority: MessagePriority){
        this.message = message;
        this.priority = priority;
    }
}

然后在组件的.ts文件中,你可以这样做:

    import StatusMessage from '../../src/entities/building/ranch/administration/statusMessage';
    import { MessagePriority } from '../../enums/message-priority';
            
    export class InfoCardComponent implements OnInit {
     messagePriority: typeof MessagePriority;
                
     constructor() { 
     this.messagePriority = MessagePriority;
    }
                
    @Input() statusMessage: StatusMessage;
    ngOnInit(): void {}
}

最后这个组件的HTML是这样的:

<div class="info-card" [ngSwitch]="statusMessage.priority">
    <h2 *ngSwitchCase="this.messagePriority.REGULAR" class="info-card__regular-message">{{statusMessage.message}}</h2>
    <h2 *ngSwitchCase="this.messagePriority.WARNING" class="info-card__warning-message">{{statusMessage.message}}</h2>
    <h2 *ngSwitchCase="this.messagePriority.IMPORTANT" class="info-card__important-message">{{statusMessage.message}}</h2>
</div>

注意,枚举首先用“typeof messagpriority”类型声明给类,然后用“this”调用定义来绑定到类。messagpriority = messagpriority "

我的组件使用MyClass类型的对象myClassObject,它本身使用MyEnum。这导致了上面描述的相同问题。解决方法是:

export enum MyEnum {
    Option1,
    Option2,
    Option3
}
export class MyClass {
    myEnum: typeof MyEnum;
    myEnumField: MyEnum;
    someOtherField: string;
}

然后在模板中使用这个

<div [ngSwitch]="myClassObject.myEnumField">
  <div *ngSwitchCase="myClassObject.myEnum.Option1">
    Do something for Option1
  </div>
  <div *ngSwitchCase="myClassObject.myEnum.Option2">
    Do something for Option2
  </div>
  <div *ngSwitchCase="myClassObject.myEnum.Option3">
    Do something for Opiton3
  </div>
</div>

从rc开始。6 / final

...

export enum AdnetNetworkPropSelector {
    CONTENT,
    PACKAGE,
    RESOURCE
}

<div style="height: 100%">
          <div [ngSwitch]="propSelector">
                 <div *ngSwitchCase="adnetNetworkPropSelector.CONTENT">
                      <AdnetNetworkPackageContentProps [setAdnetContentModels]="adnetNetworkPackageContent.selectedAdnetContentModel">
                                    </AdnetNetworkPackageContentProps>
                  </div>
                 <div *ngSwitchCase="adnetNetworkPropSelector.PACKAGE">
                </div>
            </div>              
        </div>


export class AdnetNetwork {       
    private adnetNetworkPropSelector = AdnetNetworkPropSelector;
    private propSelector = AdnetNetworkPropSelector.CONTENT;
}

Angular4 -在HTML模板中使用Enum

解决方案:https://stackoverflow.com/a/42464835/802196

信用:@snorkpete

在你的组件中,你有

enum MyEnum{
  First,
  Second
}

然后在你的组件中,你通过成员'MyEnum'引入Enum类型,并为你的枚举变量'myEnumVar'创建另一个成员:

export class MyComponent{
  MyEnum = MyEnum;
  myEnumVar:MyEnum = MyEnum.Second
  ...
}

你现在可以在你的。html模板中使用myEnumVar和MyEnum。例如,在ngSwitch中使用枚举:

<div [ngSwitch]="myEnumVar">
  <div *ngSwitchCase="MyEnum.First"><app-first-component></app-first-component></div>
  <div *ngSwitchCase="MyEnum.Second"><app-second-component></app-second-component></div>
  <div *ngSwitchDefault>MyEnumVar {{myEnumVar}} is not handled.</div>
</div>