Implementing many_to_many relation with checkboxes - php

Question

I've gotten stuck on something that I believe is down to my in-experience with the many to many relationship.
In my application I am mapping interests to products with a many to many. I wish to create the following scenario whereby the full list of interests is listed under a specific product with check boxes. For every check box that is selected when the form is submitted, a row is added to the InterestProductAssignment table.
In my product controller I call the full list of interests-
$interests = Interest::model()->findAll();
Actually I don't get a lot further than this as my mind is in knots wondering where to proceed from here. What I've tried so far is building an array of InterestProductAssignment objects to match the interests array I've returned above. I've tried passing it to the view and building out the form, but I've gotten myself fairly confused by trying to match the two up and I can't believe I'm using Yii correctly as it's messy.
Is anyone able to outline a solution for this problem that enables me to have a checkbox against every interest that would add a link between the product and interest upon submitting? I'd be interested to see what you'd write in the controller and view.
Just to clarify, this page is the subject of just one product.
EXTENSION
For the supplementary problem I'm having, I'm posting the code I've got, this may also help others implement a similar thing, once we find the mistake.
My relation within my product controller reads like this-
'interests'=>array(self::MANY_MANY, 'Interest', 'interest_product_assignment(interest_id, product_id)')
Controller
public function actionUpdate($id)
{
// loadModel as been adapted to be called "->with('interests')"
$model=$this->loadModel($id);
// Uncomment the following line if AJAX validation is needed
// $this->performAjaxValidation($model);
if(isset($_POST['Product']))
{
$model->attributes=$_POST['Product'];
if($model->save())
foreach($_POST['ProductInterest'] as $i => $interest_id){
$this_interest = new InterestProductAssignment;
$this_interest->product_id = $model->id;
$this_interest->interest_id = $interest_id;
$this_interest->save();
}
$this->redirect(array('view','id'=>$model->id));
}
$this->render('update',array(
'model'=>$model,
));
}
Relevant part of view _form.php
<div class="row">
<?php echo CHtml::checkBoxList('ProductInterest', CHtml::listData($model->interests, 'interest_id', true), CHtml::listData(Interest::model()->findAll(), 'id', 'interest'));?>
</div>
The problem is that the second field in checkBoxList does not seem to properly fill in the check boxes that are already selected. I suspect that the root cause of this is likely a daft mistake. I can't spot it though and I'm not familiar enough with checkBoxList.
Thanks in advance.

Answer 1

Goose,
I think what you are looking for here is the CheckBoxList.
In your form you can use the code
echo CHtml::checkBoxList('Product_Interests', $model->getInterests(), CHtml::listData(Interest::model()->findAll(), 'interest_id', 'interest_title'));
//$model->getInterests() is a method that should returns an array of IDs of all the currently selected interests
Then in your controller you can use the code:
foreach($_POST['Product_Interests'] as $interest_id=>$checked)
if($checked)
$model->addInterest($interest_id); //Add Interest
else
$model->removeInterest($interest_id); //Remove an Interest if it exists
//Note: If you have a model that connects these tables those can be created or destroyed here