Difference between Controller and Model in MVC

I'm little confused about controller and model in MVC framework (codeIgniter). Its clear to me that controller methods calls the views and Model methods interact with database. However, I'm little confused about the following types of methods, which are called by methods in a controller.

hash_password              //returns hash password. 
valid_email               //validates email format and return true or false
is_logged                //check if session has a variable, returns true or false
generate_random_string  //generates and hashes a random string

Should they be placed in controller or in a model?

Currently I place all of the abo开发者_如何学运维ve functions in a controller. Is it correct?

I think the is_logged should be placed in the Model for User. Note that the User might be a customer in your case or any class that you have made to model a user of your service.

The valid_email and generate_random_string are more or less utility functions, which you can place in a Utility or Utilities model, so that these are reusable in various controllers in your application.

The hash_password, can be placed in either the User model or Utility model. I am more tempted to place it in Utility model, since its a hashing function and there is nothing the user cares about. However, I can imagine there can be argument(s) otherwise.

The following SO question (though for a different framework) can also serve as a rule of thumb:

Where to put custom functions in Zend Framework 1.10

generally controllers are used to determine how to handle the http requests made..

There's nothing wrong in creating some functions which directly respond to the http requests.

but if it has anything to do with the DB, its better to place those function in the model, and call them from the controller.

Controller should combine view with model, so every validation shoulde be placed in model this is my example from kohana

CONTROLLER

<?php
/**
 * User Controller
 */
class Controller_Admin_User extends Controller_Admin_Template {

    public function action_index()
    {
        $this->template->body = View::factory('admin/user/index')
                ->set('i', 0)
                ->bind('users', $users)
                ->bind('groups', $groups)
                ->bind('id_user_group', $id_user_group);

        $model_user = new Model_Admin_User;
        $users = $model_user->get_users(Arr::get($_GET, 'sort'), Arr::get($_GET, 'order'));

        $model_usergroup = new Model_Admin_Usergroup;
        $groups = $model_usergroup->get_user_group();
    }

    public function action_add()
    {
        $this->template->body = View::factory('admin/user/form_add')
                ->bind('error', $error)
                ->bind('groups', $groups)
                ->bind('post', $post);

        $model_usergroup = new Model_Admin_Usergroup;
        $groups = $model_usergroup->get_user_group();

        if($_POST)
        {
            $model_user = new Model_Admin_User;
            if($model_user->save($_POST) == false)
            {
                $error = $model_user->error;
                $post = $_POST;
            }
            else
            {
                $this->request->redirect('admin/user');
            }
        }
    }

MODEL

class Model_Back_User extends Model {

    private $qb;

    public $aliases = array(
        'id'=> 'id_user'
    );

    public $error = array(
        'name'          => null,
        'surname'       => null,
        'login'         => null,
        'password'      => null,
        'id_user_group' => null,
        'old_password'  => null,
        'new_password'  => null,
        'confirm'       => null,
        'email'         => null,
        'phone'         => null,
    );

    private $rules = array(
        'name'          => array('not_empty' => null, 'alpha' => null),
        'surname'       => array('not_empty' => null, 'alpha' => null),
        'login'         => array('not_empty' => null),
        'password'      => array('not_empty' => null),
        'id_user_group' => array('not_empty' => null),
        'email'         => array('not_empty' => null, 'email' => null),
        'phone'         => array('not_empty' => null),
        'old_password'  => array('not_empty' => null),
        'new_password'  => array('not_empty' => null),
        'confirm'       => array('matches'   => array('new_password'))
    );

    public function __construct()
    {
        $this->qb = new Querybuilder;
        //parent::__construct();
    }

    public function change_password($data)
    {       
        $validate = Validate::factory($data)
            ->filter(true,              'trim')
            ->rules('old_password',     $this->rules['old_password'])
            ->rules('new_password',     $this->rules['new_password'])
            ->rules('confirm',          $this->rules['confirm'])
            ->callback('old_password',  array($this, 'password_exists'), array('id_user'=> $data['id_user']));

        if($validate->check() == false)
        {
            $this->error = array_merge($this->error, $validate->errors('user'));
            return false;
        }

        $u = Session::instance()->get('user');
        $this->edit(array('password'=> $this->password($data['new_password'])), array('id_user'=> $u['id_user']));
        return true;
    }

    public function password_exists(Validate $valid, $field, $param)
    {
        if($this->user_exists(array('password'=> $this->password($valid[$field]), 'id_user'=> $param['id_user'])) == false)
        {
            $valid->error($field, 'old password is incorrect', array($valid[$field]));
        }
    }

    public function save($data)
    {
        $validate = Validate::factory($data)
            ->filter(true, 'trim')
            ->rules('name', $this->rules['name'])
            ->rules('surname', $this->rules['surname'])
            ->rules('user_group_id', $this->rules['id_user_group'])
            ->rules('email', $this->rules['email'])
            ->rules('phone', $this->rules['phone']);

        $edit = false;
        if(isset($data['id_user']) AND Validate::not_empty($data['id_user']))
        {
            $edit = true;
        }
        else
        {
            $validate->rules('login', $this->rules['login'])
                    ->rules('password', $this->rules['password']);
        }

        if($validate->check() == false)
        {
            $this->error = array_merge($this->error, $validate->errors('user'));
            return false;
        }

        if($edit == true)
        {
            $this->edit(
                array(
                    'name'          => $data['name'],
                    'user_group_id' => $data['user_group_id']
                ),
                array(
                    'id_user'=> $data['id_user']
                )
            );
            return true;
        }
        return $this->add(
                    array(
                        'name'          => $data['name'],
                        'login'         => $data['login'],
                        'password'      => $data['password'],
                        'user_group_id' => $data['user_group_id']
                    )
                );
    }

    protected function add($data)
    {        
        $data['password'] = $this->password($data['password']);

        return $this->_db->query(Database::INSERT, 
            $this->qb->insert('user')->set($data)->build_query()
        );
    }

View is not so important thats why i dont put this here.

Generally speaking - a model should know stuff about it's own data. So anything related purely to a model's own data - should go in the model.

Eg the hash_password and email-validation methods - a model should know how to validate or update it's own data-fields, so those should go in the model.

However a controller should know about how to direct user actions appropriately and to load the correct models for views etc.

EG the session-related method should go in the controller, because the session is used for storing the user's state (based on past actions).

The "generate random string" method is very vague and may be used everywhere. I'd put that in a separate library possibly included in the model/controller as appropriate.

I've been using Codeigniter for a long time and I'd do the following with your functions as far as placement goes:

hash_password              //returns hash password. 

I'd put something like a password hasher in a library or helper file so I could call it from my controller like:

// pretend library I'd make for tasks like hashing etc
$this->load->library('passwords');
// transform posted password into it's hashed version   
$password = $this->password_library->hash_password($this->input->post('password'));

I'm assuming you want to hash/salt the password and store it in your database in that example

valid_email               //validates email format and return true or false

This is already in form_validation, so...

is_logged                //check if session has a variable, returns true or false

This should also connect to a authentication library

generate_random_string  //generates and hashes a random string

Again, this would come from a library or helper.

SO WHEN DO YOU USE A MODEL?

Me, I use models exclusively for in/out on the database. All my queries go in there. I usually have my model's functions return data objects so I can loop through them in my views.

Controllers call your data from your models, then dump everything into your views. Outside functionality always goes into libraries and helpers. I like to do the "MY_library" and extend Codeigniter's own stuff - especially with forms and the html helper etc.