WP_Model-Geocoding.php

<?php

class City extends WP_Model
{
    public $postType = 'city';

    public $attributes = [      
        'latitude',
        'longitude'
    ];

    public function saving($model){
        $output = json_decode(file_get_contents("http://maps.google.com/maps/api/geocode/json?address=". $model->title ."&sensor=false"));
        $latitude = @$output->results[0]->geometry->location->lat;
        $longitude = @$output->results[0]->geometry->location->lng;

        if(!empty($latitude) && !empty($longitude)){ 
            $model->latitude = $latitude;
            $model->longitude = $longitude;
        }
    }
 }