bcit-ci/CodeIgniter

######
Models
######

Models are **optionally** available for those who want to use a more
traditional MVC approach.

.. contents:: Page Contents

What is a Model?
================

Models are PHP classes that are designed to work with information in
your database. For example, let's say you use CodeIgniter to manage a
blog. You might have a model class that contains functions to insert,
update, and retrieve your blog data. Here is an example of what such a
model class might look like::

    class Blog_model extends CI_Model {

        public $title;
        public $content;
        public $date;

        public function get_last_ten_entries()
        {
            $query = $this->db->get('entries', 10);
            return $query->result();
        }

        public function insert_entry()
        {
            $this->title    = $_POST['title']; // please read the below note
            $this->content    = $_POST['content'];
            $this->date    = time();

            $this->db->insert('entries', $this);
        }

        public function update_entry()
        {
            $this->title    = $_POST['title'];
            $this->content    = $_POST['content'];
            $this->date    = time();

            $this->db->update('entries', $this, array('id' => $_POST['id']));
        }

    }

.. note:: The methods in the above example use the :doc:`Query Builder
    <../database/query_builder>` database methods.

.. note:: For the sake of simplicity in this example we're using ``$_POST``
    directly. This is generally bad practice, and a more common approach
    would be to use the :doc:`Input Library <../libraries/input>`
    ``$this->input->post('title')``.

Anatomy of a Model
==================

Model classes are stored in your **application/models/** directory.
They can be nested within sub-directories if you want this type of
organization.

The basic prototype for a model class is this::

    class Model_name extends CI_Model {

    }

Where **Model_name** is the name of your class. Class names **must** have
the first letter capitalized with the rest of the name lowercase. Make
sure your class extends the base Model class.

The file name must match the class name. For example, if this is your class::

    class User_model extends CI_Model {

    }

Your file will be this::

    application/models/User_model.php

Loading a Model
===============

Your models will typically be loaded and called from within your
:doc:`controller <controllers>` methods. To load a model you will use
the following method::

    $this->load->model('model_name');

If your model is located in a sub-directory, include the relative path
from your models directory. For example, if you have a model located at
*application/models/blog/Queries.php* you'll load it using::

    $this->load->model('blog/queries');

Once loaded, you will access your model methods using an object with the
same name as your class::

    $this->load->model('model_name');

    $this->model_name->method();

If you would like your model assigned to a different object name you can
specify it via the second parameter of the loading method::

    $this->load->model('model_name', 'foobar');

    $this->foobar->method();

Here is an example of a controller, that loads a model, then serves a
view::

    class Blog_controller extends CI_Controller {

        public function blog()
        {
            $this->load->model('blog');

            $data['query'] = $this->blog->get_last_ten_entries();

            $this->load->view('blog', $data);
        }
    }
    

Auto-loading Models
===================

If you find that you need a particular model globally throughout your
application, you can tell CodeIgniter to auto-load it during system
initialization. This is done by opening the
**application/config/autoload.php** file and adding the model to the
autoload array.

Connecting to your Database
===========================

When a model is loaded it does **NOT** connect automatically to your
database. The following options for connecting are available to you:

-  You can connect using the standard database methods :doc:`described
   here <../database/connecting>`, either from within your
   Controller class or your Model class.
-  You can tell the model loading method to auto-connect by passing
   TRUE (boolean) via the third parameter, and connectivity settings,
   as defined in your database config file will be used::

    $this->load->model('model_name', '', TRUE);

-  You can manually pass database connectivity settings via the third
   parameter::

    $config['hostname'] = 'localhost';
    $config['username'] = 'myusername';
    $config['password'] = 'mypassword';
    $config['database'] = 'mydatabase';
    $config['dbdriver'] = 'mysqli';
    $config['dbprefix'] = '';
    $config['pconnect'] = FALSE;
    $config['db_debug'] = TRUE;

    $this->load->model('model_name', '', $config);