/**
  * Parses the value of a node into the model
  * 
  * @param ValueInterface $obj
  * @param Node $node
  * @return void
  */
 private function parseValue(ValueInterface $obj, Node $node)
 {
     $value = $node instanceof Const_ ? $node->value : $node->default;
     if ($value !== null) {
         if ($this->isPrimitive($value)) {
             $obj->setValue($this->getPrimitiveValue($value));
         } else {
             $obj->setExpression($this->getExpression($value));
         }
     }
 }
 private function writeValue(ValueInterface $model)
 {
     if ($model->isExpression()) {
         $this->writer->write($model->getExpression());
     } else {
         $value = $model->getValue();
         if ($value instanceof PhpConstant) {
             $this->writer->write($value->getName());
         } else {
             $this->writer->write($this->exportVar($value));
         }
     }
 }
 protected function isValueNull(ValueInterface $obj)
 {
     $this->assertNull($obj->getValue());
 }