allow getValue to use an attribute value path

This makes it easier to get nested values from an Entity. The downside
atm would be that the setValue doesn't vehave the same as it just sets
current level attributes instead of trying to change nested ones.

refs #1

src/Runtime/Entity/Entity.php

@@ -3,8 +3,10 @@
 namespace Trellis\Runtime\Entity;
 
 use Closure;
+use JsonSerializable;
 use Trellis\Common\Error\RuntimeException;
 use Trellis\Common\Object;
+use Trellis\Runtime\Attribute\AttributeValuePath;
 use Trellis\Runtime\EntityTypeInterface;
 use Trellis\Runtime\Validator\Result\IncidentInterface;
 use Trellis\Runtime\Validator\Result\ResultMap;
@@ -13,7 +15,6 @@
 use Trellis\Runtime\ValueHolder\ValueChangedListenerInterface;
 use Trellis\Runtime\ValueHolder\ValueHolderInterface;
 use Trellis\Runtime\ValueHolder\ValueHolderMap;
-use JsonSerializable;
 
 /**
  * Entity generically implements the EntityInterface interface
@@ -182,9 +183,13 @@ public function setValues(array $values)
      */
     public function getValue($attribute_name)
     {
-        $value_holder = $this->getValueHolderFor($attribute_name);
+        if (!mb_strpos($attribute_name, '.')) {
+            $value_holder = $this->getValueHolderFor($attribute_name);
+            return $value_holder->getValue();
+        } else {
+            return AttributeValuePath::getAttributeValueByPath($this, $attribute_path);
+        }
 
-        return $value_holder->getValue();
     }
 
     /**