cakephp hasmany form data - cakephp

Question

I want to save multiple categories for a product.
I have the models:
Category.php
public $hasAndBelongsToMany = array(
'Product' => array(
'className' => 'Product',
'joinTable' => 'product_categories',
'foreignKey' => 'category_id',
'associationForeignKey' => 'product_id',
'unique' => 'keepExisting',
)
);
Product.php
public $hasMany = array(
'ProductCategory' => array(
'className' => 'ProductCategory',
'foreignKey' => 'product_id',
'dependent' => false,
),
ProductCategory.php
public $belongsTo = array(
'Product' => array(
'className' => 'Product',
'foreignKey' => 'product_id',
),
'Category' => array(
'className' => 'Category',
'foreignKey' => 'category_id',
)
);
So in Product/add view I add a set of checkboxes of the Categories by:
echo $this->Form->input('ProductCategory.category_id',array(
'label' => __('Category',true),
'type' => 'select',
'multiple' => 'checkbox',
'options' => $categories
));
But this produces a set of inputs with the names of: name="data[ProductCategory][category_id][]" rather than name="data[ProductCategory][0][category_id]" the zero being incremented.
If they are in the format with the key between the model and field then I can use saveAll()?
As it is in the format I am getting I would have to manipulate the request->data to get it into the form I want to be able to save()
Am I going about this the correct way? Or maybe my models are set up incorrectly?
Also, what happens with editing hasMany data? What if for instance I uncheck an option and add another? Does cake automatically delete all associated records before adding new ones?
EDIT.
Essentially what I am asking is is there a better or quicker way of doing this, which works right now:
if ($this->Product->save($this->request->data)) {
$this->Product->ProductCategory->deleteAll(array('ProductCategory.product_id' => $this->Product->id));
foreach ($this->request->data['ProductCategory']['category_id'] as $cat_id) {
$this->Product->ProductCategory->create();
$this->Product->ProductCategory->set(array(
'product_id' => $this->Product->id,
'category_id' => $cat_id
));
$this->Product->ProductCategory->save();
}
}

Answer 1

in your form iterate however many you wish to display along the lines of
for/while/do()
{
$counter++
$this->Form->text('Product.'.$counter.'.price');
$this->Form->text('Product.'.$counter.'.description');
}

Answer 2

I would use saveAll() for this as it's designed to save a record and all it's related records for you automatically, assuming that your id's are in the data and it's formatted correctly.
http://book.cakephp.org/2.0/en/models/saving-your-data.html#model-saveall-array-data-null-array-options-array