Create Presenters like Jamie Rumbelow's book

[eluser]Lykos22[/eluser]
Hi, I'd like some help please. I have read Jamie Rumbelow's "CodeIgniter Handbook" about Presenters
and I'm trying to show them on action.

I have created the Presenter class inside my application/presenter/presenter.php and auto-loaded through the config file.

My question is how can I pass through the presenter something like this below in order to work correct?

Code:

$this->data['post'] = (isset($id)) ? $this->post_model->get_by_id($id) : $this->post_model->init();