Use assets as a service.

module/config/services.php

@@ -10,6 +10,7 @@
  */
 
 use Netzmacht\Contao\Leaflet\Boot;
+use Netzmacht\Contao\Leaflet\ContaoAssets;
 use Netzmacht\Contao\Leaflet\Frontend\Helper\FrontendApi;
 use Netzmacht\Contao\Leaflet\Frontend\ValueFilter;
 use Netzmacht\Contao\Leaflet\Mapper\DefinitionMapper;
@@ -38,10 +39,17 @@ $container['leaflet.map.service'] = $container->share(function ($container) {
         $container['leaflet.definition.mapper'],
         $container['leaflet.definition.builder'],
         $container['event-dispatcher'],
-        $container['input']
+        $container['input'],
+        $container['leaflet.map.assets']
     );
 });
 
+/*
+ * Contao assets handler. Loads Leaflet assets as contao (static) assets.
+ */
+$container['leaflet.map.assets'] = $container->share(function () {
+    return new ContaoAssets();
+});
 
 /*
  * The leaflet boot.

src/Netzmacht/Contao/Leaflet/MapService.php

@@ -59,6 +59,13 @@ class MapService
      */
     private $input;
 
+    /**
+     * Map assets collector.
+     *
+     * @var Assets
+     */
+    private $assets;
+
     /**
      * Construct.
      *
@@ -66,17 +73,20 @@ class MapService
      * @param Leaflet          $leaflet         The Leaflet instance.
      * @param EventDispatcher  $eventDispatcher The Contao event dispatcher.
      * @param \Input           $input           Thw request input.
+     * @param Assets           $assets
      */
     public function __construct(
         DefinitionMapper $mapper,
         Leaflet $leaflet,
         EventDispatcher $eventDispatcher,
-        \Input $input
+        \Input $input,
+        Assets $assets
     ) {
         $this->mapper          = $mapper;
         $this->leaflet         = $leaflet;
         $this->eventDispatcher = $eventDispatcher;
         $this->input           = $input;
+        $this->assets          = $assets;
     }
 
     /**
@@ -147,11 +157,10 @@ class MapService
         $style = ''
     ) {
         $definition = $this->getDefinition($mapId, $filter, $elementId);
-        $assets     = new ContaoAssets();
         $template   = \Controller::getTemplate($template);
 
         // @codingStandardsIgnoreStart - Set for the template.
-        $javascript = $this->leaflet->build($definition, $assets);
+        $javascript = $this->leaflet->build($definition, $this->assets);
         $mapId      = $definition->getId();
         // @codingStandardsIgnoreEnd