diff --git a/src/cart.php b/src/cart.php
index 233ca5c..07badef 100644
--- a/src/cart.php
+++ b/src/cart.php
@@ -92,13 +92,6 @@ public function addProduct( product $product, $qty ) : self
 		return $this;
 	}
 	//------------------------------------------------------------------------
-	public function addData( cartData $data ) : self
-	{
-		$this->data[ $data->getType() ] = $data;	
-		
-		return $this;
-	}
-	//------------------------------------------------------------------------
 	public function emptyCart() : self
 	{
 		$this->data = [];
@@ -228,37 +221,31 @@ public function save()
 		$this->storageHandler->finalize();
 	}
 	//------------------------------------------------------------------------
+	public function addData( cartData $data ) : self
+	{
+		$this->data[$data->getType()]  = $data;	
+		
+		return $this;
+	}
+	//------------------------------------------------------------------------
 	public function getCartData() : array
 	{
 		return $this->data;
 	}
 	//------------------------------------------------------------------------
-	public function getDataByCartDataType( string $type ) 
+	public function hasCartDataType( string $type ) : bool
 	{
-		if( count($this->data) > 0 )
-		{
-			foreach( $this->data as $cartData )
-			{
-				if( $cartData->isValidType( $type ) == false )
-				{
-					throw new \Exception("Invalid card data type : ".$type, 1);
-				}
-
-				if( $cartData->getType() == $type )
-				{
-					return $cartData->getDataArray();
-				}
-				else
-				{
-					continue;
-				}
-			}
-			return [];
-		}
-		else
+		return array_key_exists( $type, $this->data );
+	}
+	//------------------------------------------------------------------------
+	public function getDataByType( string $type ) : array
+	{
+		if( ! $this->hasCartDataType( $type ) )
 		{
-			return (array) $this->data;
+			throw new \Exception( 'Invalid cart data type: ' . $type );
 		}
+
+		return $this->data[$type];
 	}
 	//------------------------------------------------------------------------
 	public function getCartItems() : array
diff --git a/src/cartData.php b/src/cartData.php
index e26a593..11abc9f 100644
--- a/src/cartData.php
+++ b/src/cartData.php
@@ -1,74 +1,36 @@
 <?php namespace treehousetim\shopCart;
 use \stdClass, \Exception, \ReflectionClass;
-class cartData
-{
-	const tOBJ = 'object';
-	const tARR = 'array';
-	const tMetalAllocation = 'metalAllocation';
-	const tCharges = 'Charges';
-	const tPaymentMethod = 'paymentMethod';
-
 
+abstract class cartData implements jsonSerializable
+{
 	protected $data;
 	protected $type;
 
 	//------------------------------------------------------------------------
-	public function setType( string $type )
-	{
-		switch( $type )
-		{
-		case self::tOBJ:
-		case self::tARR:
-		case self::tMetalAllocation:
-		case self::tCharges:
-		case self::tPaymentMethod:
-			$this->type = $type;
-			break;
-
-		default:
-			throw new Exception( 'Unknown type: ' . $type );
-		}
-
-		return $this;
-	}
+	abstract public function jsonSerialize();
 	//------------------------------------------------------------------------
-	static function getConstants() {
-        $oClass = new ReflectionClass(__CLASS__);
-        return $oClass->getConstants();
-    }
-	//------------------------------------------------------------------------
-	public function isValidType( string $type ): bool
+	public function getForStorage()
 	{
-		return in_array($type, self::getConstants());
+		return $this->jsonSerialize();
 	}
 	//------------------------------------------------------------------------
-	//for now we are not planning to use this and use setDataArray for now.
-	public function setDataObject( object $data ) : self
+	public function setData( $data ) : self
 	{
-		throw new Exception("Use setDataArray instead.", 1);
-		
-		$this->setType( self::tOBJ );
 		$this->data = $data;
 		return $this;
 	}
 	//------------------------------------------------------------------------
-	public function setData( array $data ) : self
+	public function getData()
 	{
-		//$this->setType( self::tARR );
-		$this->data = $data;
-		return $this;
+		return $this->data;
 	}
 	//------------------------------------------------------------------------
-	public function getDataObject() : object
+	public function setType( string $type ) : self
 	{
-		return (object)$this->data;
+		$this->type = $type;
+		return $this;
 	}
 	//------------------------------------------------------------------------
-	public function getDataArray() : array
-	{
-		return (array)$this->data;
-	}
-
 	public function getType()
 	{
 		return $this->type;
diff --git a/src/cartStorageSession.php b/src/cartStorageSession.php
index df3e3dd..928a6e4 100644
--- a/src/cartStorageSession.php
+++ b/src/cartStorageSession.php
@@ -40,9 +40,9 @@ public function saveData( array $data )
 
 		$_SESSION['cart_data'] = [];
 
-		foreach( $this->data as $data )
+		foreach( $data as $type => $_data )
 		{
-			$_SESSION['cart_data'][] = $data;
+			$_SESSION['cart_data'][$type] = $data->getForStorage();
 		}
 
 		return $this;
@@ -72,8 +72,9 @@ public function loadCart( cart $cart ) : cartStorageInterface
 
 		$data = $_SESSION['cart_data'] ?? array();
 
-		foreach( $data as $cartData )
+		foreach( $data as $type => $cartData )
 		{
+			$cartData->setType( $type );
 			$cart->addData( $cartData );
 		}