The Dependency Injection

Having a service in place, now we can delegate the news assignment task to it. To do so, first import the service class into the component class:

// app/collector/collector.component.ts 
import {Component} from '@angular/core'; 
import {CollectorService} from './collector.service'; 
//... 

Now we need to create that service and pass it to this component. Technically, we don't need to do it ourselves. There is a framework called Dependency Injection and it is in charge of instantiating that service for us.

The Dependency Injection framework looks for all dependencies for a particular class and automatically initializes--injects--them all. All the Dependency Injection framework needs to know is where that service lives. In other words, it needs the name of the service provider.

We can inform the Dependency Injection framework about the service(s) we are interested in via providers metadata as follows:

// app/collector/collector.component.ts 
//... 
@Component({ 
  selector...