get value from provider function into another page

Question

I am trying to get the result from a function found in my provider to another page in my app. In this case the result is the "cityname". I get an undefined when console logging out the response.

location provider ts

  getLocation(cityname) {
      this.options = {
      enableHighAccuracy: false
  };
  return this.geolocation.getCurrentPosition(this.options).then((pos: Geoposition) => {
    var geocoder = new google.maps.Geocoder;
    var latlng = new google.maps.LatLng(pos.coords.latitude, pos.coords.longitude);
    geocoder.geocode({'location': latlng}, function(results, status) {
        if (status === google.maps.GeocoderStatus.OK) {
          if (results[1]) {
            var cityname = results[1].formatted_address;
            return cityname;
          } else {
            console.log('No results found');
          }
        } else {
          console.log('Geocoder failed due to: ' + status);
        }
      });
  }, (err: PositionError) => {
      console.log("error : " + err.message);
  }) 
  }

another page

import { LocationProvider } from './../../../../providers/location/location';

  constructor(public navCtrl: NavController, public navParams: NavParams, public storage: Storage, private location: LocationProvider) {}

  ionViewWillEnter() {

       this.location.getLocation().then((data) =>{
         console.log(data);
       });

  }  

Any ideas what I'm doing wrong. The purpose is to get the city name to be re-used in other parts of my pp

Answer 1

Your code doesnt make sense as currently written :

1. You don't use the variable cityname in getLocation implementation
2. There is a mismatch between the signatures getLocation() (in another page ) and getLocation(cityname) (in location provider )
3. The Google Maps API gives you access to a callback and not a promise. As written now, your method doenst return anything. You must transofrm the callback in to a promise as explained in Promises With Google Maps Geocoder API

I suggest that you resolve your issues by cleaning up a bit :

location provider

getLocation() { // remove cityname from the signature, it is not used anyway
      this.options = {
      enableHighAccuracy: false
  };
  return this.geolocation.getCurrentPosition(this.options).then((pos: Geoposition) => {
    var geocoder = new google.maps.Geocoder;
    var latlng = new google.maps.LatLng(pos.coords.latitude, pos.coords.longitude);

    return new Promise(function(resolve, reject) {
        geocoder.geocode({'location': latlng}, function(results, status) {
            if (status === google.maps.GeocoderStatus.OK) {
               if (results[1]) {
                   var cityname = results[1].formatted_address;
                   resolve(cityname)
               } else {
                   reject('No results found');
               }
             } else {
                 reject('Geocoder failed due to: ' + status);
             }
      });
    })
  }

Answer 2

您的代码中可能还存在其他问题，但是我注意到的第一件事是，在another page您调用了不带参数的getLocation() ，而该函数被定义为使用cityname作为参数。