src/Form/Container.php
public function executeAction($name, array $data = [])
    {
        if (false !== strpos($name, '.')) {
            list($name, $childKey) = explode('.', $name, 2);
            $container = $this->getForm($name);
            
            // execute child container's action
            return $container->executeAction($childKey, $data);
        }
        
        // this container defines no actions
        return [];
    }
public function executeAction($name, array $data = [])
    {
        if (false !== strpos($name, '.')) {
            list($name, $childKey) = explode('.', $name, 2);
            $container = $this->getForm($name);
            
            // execute child container's action
            return $container->executeAction($childKey, $data);
        }
        
        // this container defines no actions
        return [];
    }
Execute an arbitrary action

@param string $name Name of an action
@param array $data Arbitrary data
@return array