Angular 2 - Can't resolve all parameters for component: (?)

Question

I started an Angular2 app and I have an issue since days !

Can\'t resolve all parameters for HomeComponent: (?).(…) 

But my issue is not a

Answer 1

My problem ended up being nothing. I simply restarted the webpack watcher and then everything was fine. For reference, I'm using the Angular CLI.

Answer 2

The issue that raised this error for me was completely different. I had a logging category in the component that I had mistakenly used in the service, and thus the service had a dependency on the component and wasn't able to be created in time for it to be injected into the component.

TL;DR: Check the imports on the service that can't be injected.

Answer 3

Import this

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

And change your constructor to

constructor(@Inject(AuthService) _authService: AuthService) 
{

}

you should @Inject any service into constructor before using it.

and your service should be injectable

@Injectable()
export class AuthService {

}

Answer 4

Make sure you have

"emitDecoratorMetadata": true,

in your tsconfig.js. You should not need to add @Inject() to your function parameters if that's enabled.