Typescript : Call instance method

Question

I have an interface:

export interface ISearchService {
    search(terms: string):  Observable<any>;
}

I have two services implementing this interface:

SearchMaleEmployeeService:

@Injectable()
export class SearchMaleEmployeeService implements ISearchService {

  constructor() { }

  public search(terms: string): Observable<any> {
    console.log('call: SearchMaleEmployeeService.search ' + terms);
  }
}

SearchFemaleEmployeeService:

@Injectable()
export class SearchFemaleEmployeeService implements ISearchService {

  constructor() { }

  public search(terms: string): Observable<any> {
    console.log('call: SearchFemaleEmployeeService.search ' + terms);
  }
}

In my search.component, I would like to call the search method of the service.

My search.component:

export class SearchComponent {
  constructor(@Inject('ISearchService') private searchService: ISearchService) { }

  onSearch(terms: string) {    
    this.searchService.search(terms);
  }
}

And finally, in the component which hosts SearchComponent:

providers: [
    { provide: 'ISearchService', useValue: SearchFemaleEmployeeService}
],

When I run the onSearch method in SearchComponent, I got this error:

EXCEPTION: Error in ./SearchComponent class SearchComponent - inline template:0:127 caused by: this.searchService.search is not a function

I think this is because I'm trying to call a method from a interface, but when I console.log this.searchService, it returns SearchFemaleEmployeeService, that mean that this is the good instance. Why do I have this error?

Paul Samsotha · Accepted Answer · 2016-10-16 14:23:17Z

2

Because you're using useValue

{provide: 'ISearchService', useValue: SearchFemaleEmployeeService}

which just uses the value you provide, which is a class, which in JS is a function. You should instead use useClass, then Angular will create it for you.

{provide: 'ISearchService', useClass: SearchFemaleEmployeeService}

answered Oct 16, 2016 at 14:23

Paul Samsotha

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