InterfaceType creation

src/InterfaceTypeCreator.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Chillu\GraphQL;
+
+use GraphQL\Type\Definition\InterfaceType as BaseInterfaceType;
+
+class InterfaceTypeCreator extends TypeCreator {
+
+    protected function getTypeResolver()
+    {
+        if(!method_exists($this, 'resolveType'))
+        {
+            return null;
+        }
+
+        $resolver = array($this, 'resolveType');
+        return function() use ($resolver)
+        {
+            $args = func_get_args();
+            return call_user_func_array($resolver, $args);
+        };
+    }
+
+    /**
+     * Get the attributes from the container.
+     *
+     * @return array
+     */
+    public function getAttributes()
+    {
+        $attributes = parent::getAttributes();
+
+        $resolver = $this->getTypeResolver();
+        if(isset($resolver))
+        {
+            $attributes['resolveType'] = $resolver;
+        }
+
+        return $attributes;
+    }
+
+    public function toType()
+    {
+        return new BaseInterfaceType($this->toArray());
+    }
+
+}

src/TypeCreator.php

@@ -53,6 +53,14 @@ public function fields()
         return [];
     }
 
+    /**
+     * @return array
+     */
+    public function interfaces()
+    {
+        return [];
+    }
+
     /**
      * Returns field structure with field resolvers added.
      *
@@ -106,14 +114,22 @@ public function toArray()
 
     public function getAttributes()
     {
-        return array_merge(
+        $interfaces = $this->interfaces();
+
+        $attributes = array_merge(
             $this->attributes(),
             [
                 'fields' => function () {
                     return $this->getFields();
                 },
             ]
         );
+
+        if(sizeof($interfaces)) {
+            $attributes['interfaces'] = $interfaces;
+        }
+
+        return $attributes;
     }
 
     /**