How to write service?

[ivanff]

I can't get routerExtension inside callback when i write service

component:

`
@component({
selector: 'app-sporttrack',
templateUrl: './sporttrackSearch.component.html',
styleUrls: ['./sporttrack.component.scss']
})
export class SporttrackSearchComponent implements OnInit, OnDestroy {
constructor(public routerExtensions: RouterExtensions, private nfc: SporttrackNfcService, public zone: NgZone) {
}

ngOnInit(): void {
    this.nfc.doStartTagListener.bind(this)
    this.nfc.doStartTagListener(this.searchAthlet).then(() => console.log(this))
}

ngOnDestroy(): void {
    this.nfc.doStopTagListener()
}

searchAthlet(data: NfcTagData) {
    this.routerExtensions.navigate(['sporttrack', athlet.phone])
}

}

`
service

`
@Injectable({
providedIn: 'root'
})
export class SporttrackNfcService {
nfc: Nfc

constructor() {
    this.nfc = new Nfc()
}

doStartTagListener(fn: (data: NfcTagData) => any): Promise<any> {
    return this.nfc.setOnTagDiscoveredListener((data: NfcTagData) => {
        console.dir(data, this.nfc)
        console.log('Tag discovered sporttrack scan! ' + JSON.stringify(data))
        fn(data)
    }).then(() => {
        console.log('OnTagDiscovered Listener set')
    }, (err) => {
        console.log(err)
    })
}

doStopTagListener() {
    this.nfc.setOnTagDiscoveredListener(null).then(() => {
        console.log('OnTagDiscovered nulled')
    }, (err) => {
        console.log(err)
    })
}

}

`

ERROR
`

Tag discovered sporttrack scan! {"id":[4,72,-37,26,-32,95,-127],"techList":["android.nfc.tech.NfcA","android.nfc.tech.MifareUltralight","android.nfc.tech.NdefFormatable"]}
JS: 123
JS: Unhandled Promise rejection: Cannot read property 'routerExtensions' of undefined ; Zone: ; Task: Promise.then ; Value: TypeError: Cannot read property 'routerExtensions' of undefined TypeError: Cannot read property 'routerExtensions' of undefined
JS: at file:///src/app/sporttrack/sporttrack.component.ts:243:21
JS: at file:///node_modules/nativescript-plugin-firebase/firebase.js:2348:51
JS: at Array.map ()
JS: at QuerySnapshot.push.../node_modules/nativescript-plugin-firebase/firebase.js.QuerySnapshot.forEach file:///node_modules/nativescript-plugin-firebase/firebase.js:2348:0
JS: at file:///src/app/sporttrack/sporttrack.component.ts:241:21
JS:

`

[ivanff]

ngOnInit(): void { this.zone.runOutsideAngular(() => { this.nfc.doStartTagListener(this.searchAthlet.bind(this)) }) }

doStartTagListener(fn: (data: NfcTagData) => any): Promise<any> { return this.nfc.setOnTagDiscoveredListener((data: NfcTagData) => { console.dir(data, this.nfc) console.log('Tag discovered sporttrack scan! ' + JSON.stringify(data)) this.zone.run(() => fn(data)) }).then(() => { console.log('OnTagDiscovered Listener set') }, (err) => { console.log(err) }) }

[ivanff]

I resolve this