如何在GeocoderService中存储来自geocoder.geocode（）的地址并将其返回给app.component？

Question

I'm really new to angular and TypeScript, I am working on application which uses google maps to find address and I can't store address from geocoder.geocode().

I tried solution from here: How do I return a variable from Google Maps JavaScript geocoder callback?

and it is ok, the alert() is working but what I want to do is to pass address from GeocoderService to a parent component and store it there. I tried to store it in service itself but I can't!

GeocoderService:

initialize() {
    this.geocoder = new google.maps.Geocoder();
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    this.codeLatLng(function(addr){
      this.loc = addr; // <= here i can't store address it is undefined
      alert(addr);
      return this.loc;
    });

  }

  codeLatLng(callback) {
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    if (this.geocoder) {
      this.geocoder.geocode({'location': latlng}, function(results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
          if (results[1]) {
            callback(results[1].formatted_address);
          } else {
            alert("No results found");
          }
        } else {
          alert("Geocoder failed due to: " + status);
        }
      });
    }
  }

app.component:

 constructor( private geolocationService: GeolocationService,
    private geocoderService: GeocoderService){
    this.position = {latitude: 0, longitude: 0}
    this.LatLng = new google.maps.LatLng( this.position.latitude, this.position.longitude);
  }

findMe(){
    this.geolocationService.getPosition().then((position: any) => {
      this.position = {latitude:position.coords.latitude,longitude: position.coords.longitude}
      this.LatLng = new google.maps.LatLng( this.position.latitude, this.position.longitude);
      this.map.setCenter(this.LatLng);
      this.loc = this.geocoderService.initialize(); //<= here i need this address to be returned and stored
      console.log(this.loc) // <= undefined
    })
 }

app.component.html:

<div #map style= "width:100%;height:400px"></div>
<button (click) = "findMe()">Find me</button>

Please help and sorry if question is dumb

Answer 1

1)

   function(addr){
          this.loc = addr; // <= here i can't store address it is undefined
          alert(addr);
          return this.loc;
        }

this function is a callback function so you cannot return data from a callback function The reason why you have undefined loc variable, is because "This" of app component class has been shadowed by the "This" of the function so to resolve this issue you have to use the arrow function (but it does not resolve your problem)

this.codeLatLng(addr=> this.loc = addr);

2)

  this.loc = this.geocoderService.initialize(); 

you will never get a value because initialize does not return a value

3) So what you have to do

Since the result of codeLatLng is asynchronous try to use Subject Or Observable object and in the app component subsribe to this object