@nativescript/template-master-detail/app/cars/shared/car-service.js

Master-detail interface to display collection of items from json collection and inspect and edit selected item properties.

import { catchError } from 'rxjs/operators'
import { Observable, throwError } from 'rxjs'
import { Car } from './car-model'
import ApiService  from "~/services/api.service";

const editableProperties = [
  'doors',
  'imageUrl',
  'luggage',
  'name',
  'price',
  'seats',
  'transmission',
  'class',
]

export function CarService() {
  if (CarService._instance) {
    throw new Error('Use CarService.getInstance() instead of new.')
  }

  this._cars = []
  this._subscriptionMap = new Map()
  CarService._instance = this

  this.getSubscription = function (key) {
    return this._subscriptionMap.get(key)
  }

  this.setSubscription = function (key, value) {
    this._subscriptionMap.set(key, value)
  }

  this.load = function () {
    return new Observable((observer) => {
      const path = 'cars'
      const onValueEvent = (snapshot) => {
        const results = this._handleSnapshot(snapshot)
        observer.next(results)
      }

      ApiService.addValueEventListener(onValueEvent, `/${path}`)
    }).pipe(catchError(this._handleErrors))
  }

  this.update = function (carModel) {
    const updateModel = cloneUpdateModel(carModel)

    return ApiService.update(`/cars/${carModel.id}`, updateModel)
  }

  this.uploadImage = function (remoteFullPath, localFullPath) {
    return ApiService.uploadFile({
      localFullPath,
      remoteFullPath,
      onProgress: null,
    })
  }

  this._handleSnapshot = function (data) {
    this._cars = []

    if (data) {
      for (const id in data) {
        if (data.hasOwnProperty(id)) {
          this._cars.push(new Car(data[id]))
        }
      }
    }

    return this._cars
  }

  this._handleErrors = function (error) {
    return throwError(error)
  }
}

CarService.getInstance = function () {
  return CarService._instance
}

CarService._instance = new CarService()

function cloneUpdateModel(car) {
  return editableProperties.reduce((a, e) => ((a[e] = car[e]), a), {}) // eslint-disable-line no-return-assign, no-sequences
}