Create a dynamic conditional validation in Cakephp - php

Question

I want to set these validation rule in CakePHP
Rule:
One of these fields is required but not both.
discount_percent
discount_amount
If discount_amount is input as 0 a NULL should be saved and then discount_percent is required to be > 1 but <=100.
If discount_percent is input a 0 then a NULL should be saved and then discount_amount is required to be > 0 but <= products.price for the selected product.
I have tried but not getting right way to perform this validation.
Modal Code:
App::uses('AppModel', 'Model');
class Code extends AppModel {
public $validate = array(
'discount_amount' => array(
'rule' => array('checkLimit'),
'message' => 'Please supply a valid discount_amount'
),
'discount_percent' => array(
'rule' => array('checkLimit'),
'message' => 'Please supply a valid discount_percent'
)
);
public function checkLimit($field) {
$passed = true;
if (isset($this->data[$this->alias]['discount_amount']) && empty($this->data[$this->alias]['discount_amount'])) {
??????
} else {
??????
}
}
}

Answer 1

Validation rules should not change any data!
So "if 0, save null" is not allowed in a validation rule.
You should implement that logic in a beforeSave() callback rather.
Regarding the validation, there is a second parameter provided containing all the $data you could use to validate other fields (and pull additional required data from the database - your product price probably).
Good documentation is at http://book.cakephp.org/2.0/en/models/data-validation.html#adding-your-own-validation-methods

Answer 2

Be careful using empty and isset, they're not exact opposites. empty('0') returns true, while isset('0') also return true. I think you want to use isset and !isset instead.
public function checkLimit($field) {
if ((!isset($this->data[$this->alias]['discount_amount']) && isset($this->data[$this->alias]['discount_percent'])) {
//only percent is set
if ($this->data[$this->alias]['discount_percent'] >= 1 && $this->data[$this->alias]['discount_percent'] <= 100) {
//percent is in correct range
return true;
}
} else if ((isset($this->data[$this->alias]['discount_amount']) && !isset($this->data[$this->alias]['discount_percent'])) {
//only amount is set
if ($this->data[$this->alias]['discount_amount'] >= 0 && $this->data[$this->alias]['discount_amount'] <= $products.price) {
//amount is in correct range
return true;
}
}
//either neither or both fields are set, or values aren't in correct range
return false;
}