src/Route.php
public function handler($handler = null)
    {
        if (func_num_args() === 0) {
            return $this->_handler;
        }
        $this->_handler = $handler;
        return $this;
    }
public function handler($handler = null)
    {
        if (func_num_args() === 0) {
            return $this->_handler;
        }
        $this->_handler = $handler;
        return $this;
    }
Gets/sets the route's handler.

@param  array      $handler The route handler.
@return array|self