permission.ts

import { Injectable } from '@angular/core';
import { Platform } from 'ionic-angular';
import { Diagnostic } from '@ionic-native/diagnostic';
 
 
@Injectable()
export class PermissionsService {
 
    constructor(
        public _platform: Platform,
        public diagnostic: Diagnostic
    ) {
    }

    checkCameraPermissions() {
      return new Promise(resolve => {
        this.diagnostic.requestCameraAuthorization().then(authorisation => {
            resolve(authorisation == this.diagnostic.permissionStatus.GRANTED);
        });
      } 
    }
 }