It appears that the Angular 2 @Injectable feature is not functioning correctly

After researching how to create a service for my Angular 2 component with TypeScript, I found that most tutorials recommend using the @Injectable decorator. However, when I tried to inject my service into my component, it didn't work as expected. Surprisingly, using @Inject seemed to do the trick.

This is the code for my service:

    import { Injectable } from '@angular/core';
    import { Observable } from 'rxjs';

    @Injectable()
    export class GeolocationService {

    /**
     * Get the current location of the user
     * @return {Observable<any>} An observable with the location of the user.
     */
    public getLocation(): Observable<any> {
        return Observable.create(observer => {
            if (window.navigator && window.navigator.geolocation) {
                window.navigator.geolocation.getCurrentPosition(position => {
                    observer.next(position);
                    observer.complete();
                }, error => {
                    observer.error(error);
                }, {
                    maximumAge: 0
                });
            } else {
                observer.error('Browser does not support location services');
            }
        });
    }
}

Here is the initial version of my component that did not work (v1):

import { GeolocationService } from './geolocation.service';

@Component({
    templateUrl: 'home.component.html',
    styleUrls: [ 'home.component.scss' ],
    providers: [ GeolocationService ]
})
export class HomeComponent implements OnInit {

    constructor(private myService: GeolocationService) {
        this.myService.getLocation()
            .subscribe(position => console.log('my position', position));
            // .error(err => console.log('oop error', err))
    }
}

And here is the updated working version of my component (v2):

import { GeolocationService } from './geolocation.service';

@Component({
    templateUrl: 'home.component.html',
    styleUrls: [ 'home.component.scss' ],
    providers: [ GeolocationService ]
})
export class HomeComponent implements OnInit {

    constructor(@Inject(GeolocationService) private myService: GeolocationService) {
        this.myService.getLocation()
            .subscribe(position => console.log('my position', position));
            // .error(err => console.log('oop error', err))
    }
}

If anyone can explain why only the second version worked correctly, I would greatly appreciate it.

Answer №1

@Inject() serves as a direct indication to Angular that a specific parameter needs to be injected. However, it is advisable not to utilize it in the manner you currently are.

In the initial scenario, it appears that you have neglected to inform your application module about the usage of the injectable. It is imperative to properly import it into your main app module and designate it as a provider. By doing so, you will have the capability to inject it into other components, as you have alerted the dependency injector that the GeolocationService class can now be injected into additional classes.

Answer №2

After some investigation, I realized that the key "emitDecoratorMetadata" was absent from my tsconfig.json file. Initially, I mistakenly thought it was called "emitDecoratorData". Despite this mix-up, I appreciate your assistance!

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