# Pipelines Pipelines # What are the available pipelines **** **** **** | Class | Description | Payload | | --------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------- | | CartItemBuilder | The process that occurs when adding an item to the cart. Extending this class allows for manipulation of the cart item before it is saved to the cart. | Aero\Cart\CartItem $item | | ContentForHead | The HTML content that will be inserted into the tag of the page. | String $content | | ContentForBody | The HTML content that will be inserted just before the closing tag of the page. | String $content | | RobotsTxt | The robots.txt file. For more information, click here. | Illuminate\Support\Collection $content | # How do I extend pipelines? The payload data can be altered using the **extend()**method. This is typically done from within a **Service Provider**. If the code is unique to a particular store it could be placed in the **boot()**method of the **AppServiceProvider**. If it is to be included as part of a module, then it can be added to the setup method of the module's **Service Provider**. For example, if a module needs to add an option to items to flag them as requiring gift wrap, the **CartItemBuilder**pipeline class should be extended in the module's **ServiceProvider**as shown below: ``` has('gift_wrap')) { $option = CartItemOption::create('Gift wrap'); $item->addOption($option); } }); } } ``` To adjust a payload which is a simple string, ensure that the payload variable is passed by reference so that it can be directly modified: ``` \Aero\Store\Pipelines\ContentForHead::extend(function (&$content) { $content .= ""; // or ... $content .= view('my_module::script-snippet'); }); ```