Complete reword

Author: javiereguiluz

reference/dic_tags.rst

@@ -363,6 +363,7 @@ the :class:`Symfony\\Component\\HttpKernel\\CacheWarmer\\CacheWarmerInterface` i
     // src/Cache/MyCustomWarmer.php
     namespace App\Cache;
 
+    use App\Foo\Bar;
     use Symfony\Component\HttpKernel\CacheWarmer\CacheWarmerInterface;
 
     class MyCustomWarmer implements CacheWarmerInterface
@@ -371,16 +372,16 @@ the :class:`Symfony\\Component\\HttpKernel\\CacheWarmer\\CacheWarmerInterface` i
         {
             // ... do some sort of operations to "warm" your cache
 
-            // this method must return an array with the file paths of the
-            // PHP files to preload. If you don't have any, return an empty array
-            $filesToPreload = [];
+            $filesAndClassesToPreload = [];
+            $filesAndClassesToPreload[] = Bar::class;
+
             foreach (scandir($someCacheDir) as $file) {
                 if (!is_dir($file = $someCacheDir.'/'.$file)) {
-                    $filesToPreload[] = $file;
+                    $filesAndClassesToPreload[] = $file;
                 }
             }
 
-            return $filesToPreload;
+            return $filesAndClassesToPreload;
         }
 
         public function isOptional()
@@ -389,6 +390,11 @@ the :class:`Symfony\\Component\\HttpKernel\\CacheWarmer\\CacheWarmerInterface` i
         }
     }
 
+The ``warmUp()`` method must return an array with the files and classes to
+preload. Files must be absolute paths and classes must be fully-qualified class
+names. The only restriction is that files must be stored in the cache directory.
+If you don't need to preload anything, return an empty array
+
 .. deprecated:: 5.1
 
     Not returning an array from the ``warmUp()`` method with the files to