Yii Many_Many Relationship and Form - yii

Question

// Post model
return array(
'categories' => array(self::MANY_MANY, 'Category', 'categories_posts(post_id, category_id)')
);
I already have the setup of tables
posts
id, title, content
categories
id, name
categories_posts
post_id, category_i
The problem I have is that I am getting an error when creating this form:
<?php $form=$this->beginWidget('CActiveForm', array(
'id'=>'post-form',
'enableAjaxValidation'=>false,
)); ?>
<p class="note">Fields with <span class="required">*</span> are required.</p>
<?php echo $form->errorSummary($model); ?>
<div class="row">
<?php echo $form->labelEx($model,'title'); ?>
<?php echo $form->textField($model,'title',array('size'=>60,'maxlength'=>255)); ?>
<?php echo $form->error($model,'title'); ?>
</div>
<div class="row">
<?php echo $form->labelEx($model,'uri'); ?>
<?php echo $form->textField($model,'uri',array('size'=>60,'maxlength'=>255)); ?>
<?php echo $form->error($model,'uri'); ?>
</div>
<div class="row">
<?php echo $form->labelEx($model,'content'); ?>
<?php echo $form->textArea($model,'content',array('rows'=>6, 'cols'=>50)); ?>
<?php echo $form->error($model,'content'); ?>
</div>
<div class="row">
<?php // echo $form->labelEx($model,'content'); ?>
<?php echo CHtml::activeDropDownList($model,'category_id', CHtml::listData(Category::model()->findAll(), 'id', 'name')); ?>
<?php // echo $form->error($model,'content'); ?>
</div>
<div class="row buttons">
<?php echo CHtml::submitButton($model->isNewRecord ? 'Create' : 'Save'); ?>
</div>
<?php $this->endWidget(); ?>
The error is:
Property "Post.category_id" is not defined.
I am quite confused. What should I be doing to correct this?

Answer 1

I use the CAdvancedArBehavior to make this easier. I wouldn't be surprised if something like this gets rolled into the Yii core eventually either:
http://www.yiiframework.com/extension/cadvancedarbehavior/
It lets you write code like this in your controller:
$model->categories = $_POST['Post']['categories'];
I use this with the more-bugggy-than-I-would-like "Relation" widget/extension. You might need to use that to get the POST variables to structure correctly, I'm not sure.

Answer 2

I honestly thought that Yii has something like Kohana or Cake in their AR anyway. I guess I have to manually add them.
foreach ($_POST['category_id'] as $category_id)
{
$categoryPost = new CategoryPost;
$categoryPost->category_id = $category_id;
$categoryPost->post_id = $model->id;
$categoryPost->save();
}

Answer 3

Use in this way:
In controller
create object for category: $modelCat= new Category;
then in
<?php echo CHtml::activeDropDownList(**$modelCat**,'category_id', CHtml::listData(Category::model()->findAll(), 'id', 'name')); ?>