// token.ts

import { InjectionToken } from '@angular/core';

export const API_TOKEN = new InjectionToken<string>('api');

//app.module.ts

  providers: [
    { provide: API_TOKEN, useValue: '/api/pizzas' }
  ]

// service.ts

import { API_TOKEN } from './token';

@Injectable()
export class FoodService {
  constructor(
    private http: Http,
    @Inject(API_TOKEN) private api: string
  ) {}
  getFood(): Observable<any[]> {
    return this.http.get(this.api)
      .map(response => response.json());
  }
}