Enable default response transformation with bound transformers

Author: xwiz

src/Http/Response/Factory.php

@@ -93,7 +93,7 @@ public function noContent()
      *
      * @return \Dingo\Api\Http\Response
      */
-    public function collection(Collection $collection, $transformer, $parameters = [], Closure $after = null)
+    public function collection(Collection $collection, $transformer = null, $parameters = [], Closure $after = null)
     {
         if ($collection->isEmpty()) {
             $class = get_class($collection);
@@ -106,6 +106,12 @@ public function collection(Collection $collection, $transformer, $parameters = [
             $parameters = [];
         }
 
+        if($transformer !== null) {
+            $binding = $this->transformer->register($class, $transformer, $parameters, $after);
+        } else {
+            $binding = $this->transformer->getBinding($collection);
+        }
+
         $binding = $this->transformer->register($class, $transformer, $parameters, $after);
 
         return new Response($collection, 200, [], $binding);
@@ -130,7 +136,11 @@ public function item($item, $transformer, $parameters = [], Closure $after = nul
             $parameters = [];
         }
 
-        $binding = $this->transformer->register($class, $transformer, $parameters, $after);
+        if($transformer !== null) {
+            $binding = $this->transformer->register($class, $transformer, $parameters, $after);
+        } else {
+            $binding = $this->transformer->getBinding($item);
+        }
 
         return new Response($item, 200, [], $binding);
     }
@@ -153,7 +163,11 @@ public function paginator(Paginator $paginator, $transformer, array $parameters
             $class = get_class($paginator->first());
         }
 
-        $binding = $this->transformer->register($class, $transformer, $parameters, $after);
+        if($transformer !== null) {
+            $binding = $this->transformer->register($class, $transformer, $parameters, $after);
+        } else {
+            $binding = $this->transformer->getBinding($paginator->first());
+        }
 
         return new Response($paginator, 200, [], $binding);
     }

src/Transformer/Factory.php

@@ -110,7 +110,7 @@ public function transformableType($value)
      *
      * @return \Dingo\Api\Transformer\Binding
      */
-    protected function getBinding($class)
+    public function getBinding($class)
     {
         if ($this->isCollection($class) && ! $class->isEmpty()) {
             return $this->getBindingFromCollection($class);