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Data Validation

Creating custom validation rules can help to make sure the data in a Model conforms to the business rules of the application, such as passwords can only be eight characters long, user names can only have letters, etc.

The first step to data validation is creating the validation rules in the Model. To do that, use the Model::validate array in the Model definition, for example:

/app/models/user.php

<?php
class User extends AppModel
{
   var $name = 'User';

   var $validate = array(
      'login' => '/[a-z0-9\_\-]{3,}$/i',
      'password' => VALID_NOT_EMPTY,
      'email' => VALID_EMAIL,
      'born' => VALID_NUMBER
   );
}

Validations are defined using Perl-compatibile regular expressions, some of which are pre-defined in /libs/validators.php. These are:

  • VALID_NOT_EMPTY

  • VALID_NUMBER

  • VALID_EMAIL

  • VALID_YEAR

If there are any validations present in the model definition (i.e. in the $validate array), they will be parsed and checked during saves (i.e. in the Model::save() method). To validate the data directly use the Model::validates() (returns false if data is incorrect) and Model::invalidFields() (which returns an array of error messages).

But usually the data is implicit in the controller code. The following example demonstrates how to create a form-handling action:

Form-handling Action in /app/controllers/blog_controller.php

<?php
class BlogController extends AppController {

   var $uses = array('Post');

   function add ()
   {
      if (empty($this->data))
      {
         $this->render();
      }
      else
      {
         if($this->Post->save($this->data))
         {
             //ok cool, the stuff is valid
         }
         else
         {
            //Danger, Will Robinson. Validation errors.
            $this->set('errorMessage', 'Please correct errors below.');
            $this->render();
         }
      }
   }
}

The view used by this action can look like this:

The add form view in /app/views/blog/add.thtml

<h2>Add post to blog</h2>
<form action="<?php echo $html->url('/blog/add')?>" method="post">
    <div class="blog_add">
        <p>Title:
            <?php echo $html->input('Post/title', array('size'=>'40'))?>
            <?php echo $html->tagErrorMsg('Post/title', 'Title is required.')?>
        </p>
        <p>Body
            <?php echo $html->textarea('Post/body') ?>
            <?php echo $html->tagErrorMsg('Post/body', 'Body is required.')?>
        </p>
        <p><?=$html->submit('Save')?></p>
    </div>
</form>

The Controller::validates($model[, $model…]) is used to check any custom validation added in the model. The Controller::validationErrors() method returns any error messages thrown in the model so they can be displayed by tagErrorMsg() in the view.

If you’d like to perform some custom validation apart from the regex based Cake validation, you can use the invalidate() function of your model to flag a field as erroneous. Imagine that you wanted to show an error on a form when a user tries to create a username that already exists in the system. Because you can’t just ask Cake to find that out using regex, you’ll need to do your own validation, and flag the field as invalid to invoke Cake’s normal form invalidation process.

Remember to use a field name that isn’t already in the model, in order to avoid any conflicts.

The controller might look something like this:

<?php

class UsersController extends AppController
{
    function create()
    {
        // Check to see if form data has been submitted
        if (!empty($this->data['User']))
        {
            //See if a user with that username exists
            $user = $this->User->findByUsername($this->data['User']['username']);

            // Invalidate the field to trigger the HTML Helper's error messages
            if (!empty($user['User']['username']))
            {
                $this->User->invalidate('username_unique');//populates tagErrorMsg('User/username_unique')
            }

            //Try to save as normal, shouldn't work if the field was invalidated.
            if($this->User->save($this->data))
            {
                $this->redirect('/users/index/saved');
            }
            else
            {
                 $this->render();
            }
        }
    }
}

If you want to invalidate a piece of data that is outside of the Model itself, be sure to add that data to the Model using the set() method. This informs the model about that data so it can be handled properly.