如何获取Angular中的组件唯一封装ID 9

Question

I'm trying to encapsulate my element ids by adding the instance id like this:

<label for="id-{{ unique }}-name"></label>
<input id="id-{{ unique }}-name" type="text" formControlName="name">

I previously worked with this: https://stackoverflow.com/a/40140762/12858538 . But after upgrading Angular from 7 to 9 this seems deprecated. I was thinking about a simple helper service, which would generate unique ids for my app.

Something like this:

@Injectable()
export class UniqueIdService {
  private counter = 0

  constructor() {}

  public getUniqueId (prefix: string) {
    const id = ++this.counter
    return prefix + id
  }
}

inspired by lodash uniqueid

But I did rather use angulars build in ids. So my currently solution is to extract the id from the components _nghost attribute.

constructor ( private element: ElementRef, ) {
   const ngHost = 
     Object.values(this.element.nativeElement.attributes as NamedNodeMap)
     .find(attr => attr.name.startsWith('_nghost'))
     .name
   this.unique = ngHost.substr(ngHost.lastIndexOf('-') + 1)
}

But I'm not perfectly happy with this solution and I'm looking for a direct access to the id.

Does anyone know how to access this?

Answer 1

The unique ID in Angular 9 can be represented as:

_nghost   -   par    -     2
   |           |           |
 static      APP_ID   componentDef.id

In order to access componentDef.id you can do the following:

export class SomeComponent implements OnInit {
  unique = this.constructor['ɵcmp'].id;

where ɵcmp is a private variable NG_COMP_DEF

Ng-run Example

Answer 2

Neither _nghost nor ɵcmp are unique across component instances. They should not be used for that purpose.

Your UniqueIdService is the easiest and the safest solution. (The counter property could be static to be sure that every instance of the service returns unique ID).