Sample Delegate

import { Injectable } from '@angular/core';
import {Http, Response, Headers, RequestOptions} from "@angular/http";
import 'rxjs/Rx';
import {Observable} from "rxjs";
import {Post} from "./http/post.class";


@Injectable()
export class HttpService {

  constructor(private http: Http) { }

  private requestUrl: string = 'http://localhost:4000/posts';

  //Do all methods and observable options

  getData(id : number) : Observable<Post> {
    return this.http.get(
${this.requestUrl}/${id}
)
      .map(this.mapResponse)
      .catch(this.handleError)
  }

  handleError(error: any): Observable<any> {
    console.error('An error occurred', error);
    return Observable.throw(error.json() || 'Server error');
  }

  mapResponse(response : Response) : Post {
    return response.json();
  }

  addData(body : Post) : Observable<Post> {
    let bodyString = JSON.stringify(body);
    let header = new Headers({
      'Content-Type' : 'application/json'
    });
    let options = new RequestOptions({
      headers : header
    });

    return this.http.post(
${this.requestUrl}
, bodyString, options)
      .map(this.mapResponse)
      .catch(this.handleError);
  }

  updateData(body : Post) : Observable<Post> {
    let bodyString = JSON.stringify(body);
    let header = new Headers({
      'Content-Type' : 'application/json'
    });
    let options = new RequestOptions({
      headers : header
    });

    return this.http.put(
${this.requestUrl}/${body.id}
, bodyString, options)
      .map(this.mapResponse)
      .catch(this.handleError);
  }

  deleteData(body : Post) : Observable<Post> {
    return this.http.delete(
${this.requestUrl}/${body.id}
)
      .map(this.mapResponse)
      .catch(this.handleError);
  }

}