implementing_a_handler.md

Implementing a handler

You can implement your own handler using the RetailCrm\Api\Interfaces\HandlerInterface. RetailCrm\Api\Handler\AbstractHandler provides boilerplate code for the chain of responsibility. AbstractHandler::next method will call next handler in the chain. You can safely use return parent::next() in your code while using AbstractHandler.

Most of the information about how handlers operate can be found in the chain of responsibility pattern explanation. There are some specific details about handlers in the client. Client will pass desired dependencies to the handler if handler implements one of those interfaces:

• Any request handler
  • RetailCrm\Api\Interfaces\PsrFactoriesAwareInterface will inject PSR-17 factories into the handler.
• Any response handler
  • RetailCrm\Api\Interfaces\SerializerAwareInterface will inject a liip/serializer instance into the handler.
  • RetailCrm\Api\Interfaces\ApiExceptionFactoryAwareInterface will inject a Liip\Serializer\SerializerInterface instance into the handler.
  • RetailCrm\Api\Interfaces\EventDispatcherAwareInterface will inject a Psr\EventDispatcher\EventDispatcherInterface instance into the handler.

All of those interfaces above have the corresponding implementation traits in the RetailCrm\Api\Traits namespace. For example, RetailCrm\Api\Interfaces\EventDispatcherAwareInterface implementation can be found in the RetailCrm\Api\Traits\EventDispatcherAwareTrait trait.

Handlers can be used in the both chains just like callback handlers (see "using a predefined hander").