How to assign value of lat and lng on ngoninit event ?

[ahmed elbarbary]

I need to assign value of lat and lng on event ngOnInit

how to do that please 

i assign value 

this.lat

this.lng

on  ngoninit event but map not display

so How to assign values of lng and lat on event ngoninit and display map

based on vlues assigned on ngoninit

import { Component, AfterViewInit, ViewChild, ElementRef } from '@angular/core';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements AfterViewInit {
  title = 'angular-gmap';
  @ViewChild('mapContainer', { static: false }) gmap: ElementRef;
  map: google.maps.Map;
  lat = 40.73061;
  lng = -73.935242;
 


  coordinates = new google.maps.LatLng(this.lat, this.lng);

  mapOptions: google.maps.MapOptions = {
    center: this.coordinates,
    zoom: 8
  };

  marker = new google.maps.Marker({
    position: this.coordinates,
    map: this.map,
    title: 'Hello World!'
  });
  ngOnInit() {
   //here i need to assign values of lat and lng and display map based on these values
    console.log("Hi man");
   
  }
  ngAfterViewInit() {
    console.log("Hi women");
    this.mapInitializer();
  }

  mapInitializer() {
    this.map = new google.maps.Map(this.gmap.nativeElement, this.mapOptions);
    this.marker.setMap(this.map);
  }
}