[RUBY] [Map display] Display a map from the address registered by the user using the Google Maps JavaScript API and Geocoding API!

Overview

The time when the map is displayed on the post detail page from the address registered by the user using the Google Maps JavaScript API and Geocoding API is recorded as a memorandum.

environment

・ Ruby '2.5.7' ・ Rails '5.2.3'

Premise

・ You have already obtained the API key for Google Maps. -The post model (here, the Datespot model) has an address column.

【reference】 Get the API key for Google Maps

process

1. Creating a post details page

Please create the post details page according to your own specifications.

views/show.html.erb

<div class="container">
  <div class="row">
　　(abridgement)
    <div class="col-md-8">
      <h2 class="datespot-name"><%= @datespot.name %></h2>
      <div class="datespot-info">
　　　　(abridgement)
        <h4 id="address">【Street address】<%= @datespot.address %></h4>
　　　　(abridgement)
      </div>
    </div>
  </div>
</div>
<%= render "map-show" %>

2. Create a view to display the map

Create a view that displays the map.

views/_map-show.html.erb

<div class="map-container">
  <div class="map_wrapper">
    <div id="map" class="map"></div>
  </div>
</div>
<script src="https://maps.googleapis.com/maps/api/js?key=<%= ENV['GOOGLE_MAP_API_KEY']%>&callback=initMap"></script>

Let's put the obtained API key in the environment variable.

stylesheets/custom.scss

#map{
  height: 310px;
  width: 550px;
}

If you do not explicitly specify the size of the map, it will not be displayed, so be sure to specify it.

3. Define a callback function

Define the callback function described in 2.

javascripts/map-show.js

function initMap() {
  //Assign the object of the div element of the area to display the map to the variable
  var target = document.getElementById('map');
  //Marker title
  var title = $('.datespot-name').text();
  //Obtaining the address described in HTML
  var address = document.getElementById('address').textContent;
  //Generating an instance of geocoding
  var geocoder = new google.maps.Geocoder();

  //geocoder.geocode()Pass the address to and write the callback function to process
  geocoder.geocode({ address: address }, function(results, status){
  //Status is OK and results[0]Generate a map if exists
    if (status === 'OK' && results[0]){
      //Assign an instance of the map to a variable
      var map = new google.maps.Map(target, {
      //results[0].geometry.location contains latitude / longitude objects
        center: results[0].geometry.location,
        zoom: 15
      });
      //Marker generation
      var marker = new google.maps.Marker({
        position: results[0].geometry.location,
        map: map,
        animation: google.maps.Animation.DROP
      });
      //Generation of acquired coordinates
      var latlng = new google.maps.LatLng(results[0].geometry.location.lat(), results[0].geometry.location.lng());
      //Create content to display in the info window
      var content = '<div id="map_content"><p>' + title + '<br/>' + address + '<br/><a href="https://maps.google.co.jp/maps?q=' + latlng + '&iwloc=J" target="_blank" rel="noopener noreferrer">View on Google Maps</a></p></div>';
      //Create an instance of the info window
      var infowindow = new google.maps.InfoWindow({
        content: content,
      });
      //Click marker to display information window(Listener registration)
      google.maps.event.addListener(marker, 'click', function() {
        //Specify a marker in the second argument and associate
        infowindow.open(map, marker);
      });
    }else{
    //If the status is other than OK or results[0]If does not exist, an alert is displayed and processing is interrupted.
      alert("The location could not be obtained from the address.: " + status);
      return;
    }
  });
}

var target = document.getElementById ('map'); is It refers to the <div id = "map" class = "map"> </ div> in views / map-show.html.erb.

var title = $ ('.datespot-name'). text (); is It refers to <h2 class = "datespot-name"> <% = @ datesspot.name%> </ h2> in views / show.html.erb.

var address = document.getElementById ('address'). TextContent; It refers to <h4 id = "address"> [address] <% = @ datesspot.address%> </ h4> in views / show.html.erb.

result

You can now display the map on the post details page from the address registered by the user!

reference

How to use and use Google Maps API Let's use Google Maps