Added InstanceIdentifier

src/Cart.php

@@ -11,6 +11,7 @@ use Gloudemans\Shoppingcart\Contracts\Buyable;
 use Gloudemans\Shoppingcart\Exceptions\UnknownModelException;
 use Gloudemans\Shoppingcart\Exceptions\InvalidRowIDException;
 use Gloudemans\Shoppingcart\Exceptions\CartAlreadyStoredException;
+use Gloudemans\Shoppingcart\Contracts\InstanceIdentifier;
 
 class Cart
 {
@@ -68,6 +69,12 @@ class Cart
     {
         $instance = $instance ?: self::DEFAULT_INSTANCE;
 
+        if ($instance instanceof InstanceIdentifier)
+        {
+            $this->discount = $instance->getInstanceGlobalDiscount();
+            $this->instance = $instance->getInstanceIdentifier();
+        }
+
         $this->instance = sprintf('%s.%s', 'cart', $instance);
 
         return $this;

src/Contracts/InstanceIdentifier.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Gloudemans\Shoppingcart\Contracts;
+
+interface InstanceIdentifier
+{
+    /**
+     * Get the unique identifier to load the Cart from
+     *
+     * @return int|string
+     */
+    public function getInstanceIdentifier($options = null);
+
+    /**
+     * Get the unique identifier to load the Cart from
+     *
+     * @return int|string
+     */
+    public function getInstanceGlobalDiscount($options = null);
+}