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。
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>