providing optional param to injectable service constructor - Angular2

Question

There is AppComponent and SecurityService.

...
@Injectable()
export class SecurityService implements OnInit {    
    private _url: string;

    constructor(private http: Http, private name?: string) {
        this._wsUrl = 'http://myurl/' + this.name        
    }
...
}

AppComponent is one which will inject security service.

export class App {

    constructor(private security: SecurityService){

    }
    ... 
}

My question is: How can I provide this optional param value for the security service constructor?

santosh singh · Accepted Answer · 2018-01-18T09:18:34.053

1

Just add the @Optional() decorator before the constructor parameter that should only be injected if there was a provider registered.

constructor(private http: Http,@Optional() private name: string)

You can read more about Optional here

DEMO

edited Jan 18 '18 at 09:18

answered Jan 18 '18 at 08:45

santosh singh

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Thanks, can you please provide full example of providing value? – user1765862 Jan 18 '18 at 08:46
@user1765862 : check out the link in the answer – santosh singh Jan 18 '18 at 08:47
Obviously I'm missing something on your demo, I don't see how are you providing name to the injectible Car? – user1765862 Jan 18 '18 at 09:26
@user1765862 : Check now I have updated the demo code – santosh singh Jan 18 '18 at 09:39
Thanks, it's much more clear now. The only thing is that on my app I'm getting ./src/app/app.component.ts Module not found: Error: Can't resolve '@angular/core/src/di/reflective_injector ---------- Is it maybe related to angular5 version, since I'm using angular2? – user1765862 Jan 18 '18 at 10:08
I'ts wrong import import ReflectiveInjector from @angular/core – santosh singh Jan 18 '18 at 10:09

providing optional param to injectable service constructor - Angular2

1 Answers1