title: Google Maps iOS SDK heatmap not rendering
body: <p>I am following the heat map code <a href="https://developers.google.com/maps/documentation/ios-sdk/utility/heatmap" rel="noreferrer">here</a> and <a href="https://github.com/googlemaps/google-maps-ios-utils" rel="noreferrer">here</a> for the Google Maps iOS SDK, but the heat map is not rendering on my map. The Google Maps API has been added through Cocoapods, and the Google Maps iOS Utils framework has been added manually with this bridging header:</p>
  
  <pre><code>#import "GMUMarkerClustering.h"
  #import "GMUGeometryRenderer.h"
  #import "GMUHeatmapTileLayer.h"
  #import "GQTPointQuadTree.h"
  </code></pre>
  
  <p>Here is the code for adding the heat map:</p>
  
  <pre><code>func addHeatmap()  {
      heatmapLayer = GMUHeatmapTileLayer()
      heatmapLayer.map = map
      var list = [GMUWeightedLatLng]()
      do {
          if let path = Bundle.main.url(forResource: "police_stations", withExtension: "json") {
              let data = try Data(contentsOf: path)
              let json = try JSONSerialization.jsonObject(with: data, options: [])
              if let object = json as? [[String: Any]] {
                  for item in object {
                      let lat = item["lat"]
                      let lng = item["lng"]
                      let coords = GMUWeightedLatLng(coordinate: CLLocationCoordinate2DMake(lat as! CLLocationDegrees, lng as! CLLocationDegrees), intensity: 1)
                      list.append(coords)
                  }
              } else {
                  print("Could not read the JSON.")
              }
          }
      } catch {
          print(error.localizedDescription)
      }
      // Add the latlngs to the heatmap layer.
      heatmapLayer.weightedData = list
  }
  </code></pre>
  
  <p>As you can see, it is very simple. I know for a fact that it can find the data because when I print <code>list.count</code>, I get 5, which is indeed the number of entries I have in my <code>police_stations.json</code>. This is what that JSON file looks like:</p>
  
  <pre><code>[
   { "lat" : 40.71916023, "lng" : -74.0001297 },
   { "lat" : 40.73737243, "lng" : -73.98742676 },
   { "lat" : 40.73347023, "lng" : -74.00218964 },
   { "lat" : 40.71083299, "lng" : -74.00424957 },
   { "lat" : 40.79249897, "lng" : -73.96648407 }
   ]
  </code></pre>
  
  <p>In spite of the fact that all of this code is so simple, the heat map does not render, and no errors are thrown, nor are there any warnings.</p>
  
  <p>Why is this not working, and how can I make it work?</p>