# Services

Services are the place where you must set your app logic.

# Define your first service

Create a file and call it app.service.ts, then copy/paste the code below inside it:

import {Injectable} from 'moonshard';

@Injectable()
export class AppService {
  helloWorld(): string {
    return 'hello world'
  }
}

We just define the AppService class and decorate it with @Injectable decorator to can use it inside Controllers or other Services

Now go to the app.controller.ts and update it to use the app.service.ts, as shown below:

import { Controller, Get } from 'moonshard';
import { AppService } from './app.service';

@Controller()
export class UsersController {
  constructor(private appService: AppService) {}

  @Get()
  helloWorld() {
    return this.appService.helloWorld()
  }
}

We just update the code to run the app logic from the app.service.ts instead of write it directly in the Controller. This way you will build a easy to scale app.