Validation Rule not working in cakePHP

I have a registration page and within this registration page the user will be required to fill in some interest, the interests values is called from a model with the name interest.php, all values are pulling through and saves as expected.

The relationship to the user model is

var $hasAndBelongsToMany = array(
        'Interest' => array(
            'className' => 'Interest',
            'joinTable' => 'users_interests',
            'foreignKey' => 'user_id',
            'associationForeignKey' => 'interest_id',
            'unique' => true,
            'conditions' => '',
            'fields' => '',
            'order' => '',
            'limit' => '',
            'offset' => '',
            'finderQuery' => '',
            'deleteQuery' => '',
            'insertQuery' => ''
        )

Whenever I add a validation rule in interest.php the little required star appears next to the checkboxes but it is not validating at all

<label for="InterestInterestId">Interests</label>
<input type="hidden" value="" name="data[Interest][interest_id]">
<div class="checkbox">
<input id="InterestInterestId8" type="checkbox" value="8" name="data[Interest][interest_id][]">
<label for="InterestInterestId8">Interest 1</label>
</div>
<div class="checkbox">
<input id="InterestInterestId1"开发者_Go百科 type="checkbox" value="1" name="data[Interest][interest_id][]">
<label for="InterestInterestId1">Interest2</label>
</div>

in my view I call the multiple checkboxes like this

 echo $form->input('Interest.interest_id', array('label' => __l('Interests'), 'multiple' => 'checkbox'));

This is my validation rule in interest.php

$this->validate = array(

            'interest_id' => array(
                'rule' => array(
                    'equalTo',
                    '1'
                ) ,
                'message' => __l('Please select some interests')
            )
        );

Am I doing something wrong here, or missing something, any help will be appreciated!!!!

---

Found the answer with the help of this link HABTM form validation in CakePHP provided by bfavaretto

The problem was this $this->User->Interest->set($this->data);

I forgot to add it