Understanding dependency injection in angular2

Question

Here is a snippet of code

@Component({
     ... : ...
     providers: [MyService]
})
export class MyComponent{

     constructor(private _myService : MyService){
     }

     someFunction(){
          this._myService.getSomething();
     }
}

And here is my understanding / question of how this works in angular2 / typescript.

• A singleton object will be created whenever we write MyServiceto providers.
• Why give it in the constructor? Can we do it somewhere else?
• whoever calls the constructor (possibly a javascript engine), how does he know what to pass to the arguments
• or am I mistaken, is that not even an argument?

EDIT

• what if i provide providers: [MyService]on two controllers. Will he create a new instance or a choice from one?

Answer 1

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bootstrap(...), providers: [...], .

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