Add fields param for filtering attributes

Specifically, this param takes effect after all other transformations
are complete. In other words, it's not acting on the model attributes
per se, but rather on the fields displayed in the API.

See thephpleague/fractal#226

app/Http/Controllers/ApiController.php

@@ -2,6 +2,7 @@
 
 namespace App\Http\Controllers;
 
+use Illuminate\Support\Facades\Input;
 use Illuminate\Http\Request;
 use Illuminate\Http\Response;
 use Closure;
@@ -114,7 +115,9 @@ protected function select( Request $request, Closure $callback )
             return $this->respondNotFound();
         }
 
-        return response()->item($item, new $this->transformer);
+        $fields = Input::get('fields');
+
+        return response()->item($item, new $this->transformer($fields) );
 
     }
 
@@ -158,7 +161,9 @@ protected function collect( Request $request, Closure $callback )
         // Assumes the inheriting class set model and transformer
         $all = $callback( $limit, $id );
 
-        return response()->collection($all, new $this->transformer);
+        $fields = Input::get('fields');
+
+        return response()->collection($all, new $this->transformer($fields) );
 
     }
 
@@ -192,7 +197,9 @@ protected function showMutliple($ids = '')
 
         $all = $this->find($ids);
 
-        return response()->collection($all, new $this->transformer);
+        $fields = Input::get('fields');
+
+        return response()->collection($all, new $this->transformer($fields) );
 
     }
 

app/Http/Transformers/ApiTransformer.php

@@ -12,6 +12,22 @@ class ApiTransformer extends TransformerAbstract
     public $excludeIdsAndTitle = false;
     public $excludeDates = false;
 
+
+    /**
+     * Used for only returning a subset of fields.
+     * Expects a comma-separated string.
+     *
+     * @link https://github.com/thephpleague/fractal/issues/226
+     *
+     * @var string
+     */
+    protected $fields;
+
+    public function __construct($fields = null)
+    {
+        $this->fields = $fields ? explode(',', $fields) : null;
+    }
+
     /**
      * Turn this item object into a generic array.
      *
@@ -21,12 +37,14 @@ class ApiTransformer extends TransformerAbstract
     public function transform($item)
     {
 
-        return array_merge(
+        $data = array_merge(
             $this->transformIdsAndTitle($item),
             $this->transformFields($item),
             $this->transformDates($item)
         );
 
+        return $this->filterFields( $data );
+
     }
 
     protected function transformFields($item)
@@ -78,4 +96,13 @@ protected function transformDates($item)
 
     }
 
+    protected function filterFields($data)
+    {
+        if (is_null($this->fields)) {
+            return $data;
+        }
+
+        return array_intersect_key($data, array_flip((array) $this->fields));
+    }
+
 }