Form validation on a HMBTM field - CakePHP - cakephp

Question

I have a cakephp 2.2 app I'm working on that allows users to submit an expenses claim. The expenese claim is made up of many expenese which have an expense code. The relationships are as follows:
ExpenseClaim hasMany Expense
Expense belongsTo ExpenseClaim
Expense hasAndBelongsToMany ExpenseCode
I want to add validation to ensure when the form is completed the expense code must be complete for each expense but for some reason adding a normal validation rule to the expense model doesnt work, obviously I'm missing something.
Heres the validation in the expense model:
class Expense extends AppModel {
/**
* Display field
*
* #var string
*/
public $displayField = 'id';
/**
* Validation rules
*
* #var array
*/
public $validate = array(
'date' => array(
'notempty' => array(
'rule' => array('notempty'),
'message' => 'Date cannot be blank',
),
),
'sitename' => array(
'notempty' => array(
'rule' => array('notempty'),
'message' => 'Sitename cannot be blank',
),
),
'detail' => array(
'notempty' => array(
'rule' => array('notempty'),
'message' => 'Details cannot be blank',
),
),
'ExpenseCode' => array(
'multiple' => array(
'rule' => array('multiple', array('min' => 1)),
'message' => 'You need to select at least one tag',
),
),
When $this->request->data is submitted via the expenseClaim/add method it looks like this:
/app/Controller/ExpenseClaimsController.php (line 179)
array(
'submit' => 'Save',
'Expense' => array(
(int) 0 => array(
'date' => array(
'day' => '25',
'month' => '03',
'year' => '2013'
),
'sitename' => '123',
'detail' => 'test',
'ExpenseCode' => array(
'ExpenseCode' => ''
),
'billable' => '1',
'amount' => '100',
'miles' => '',
'total' => '100',
'billable_mileage' => '',
'recorded_global_mileage_rate' => '0.4'
)
),
'CashFloat' => array(
'amount' => ''
),
'ExpenseClaim' => array(
'user_id' => '16',
'claim_status_id' => '1',
'date_submitted' => '2013-03-25 18:20:53'
)
)
As you can see the ExpenseCode is empty... How can I ensure that this is not the case?

Answer 1

I managed to solve this by adding the following to my Expense model:
function beforeValidate() {
if (!isset($this->data['ExpenseCode']['ExpenseCode']) || empty($this->data['ExpenseCode']['ExpenseCode'])) {
$this->invalidate('ExpenseCode', 'Type cannot be blank');
}
return true;
}
Hope that helps someone.