Share custom validation method between given models

I want to share validation function between multiple models. Like components in controller.

I think extending AppModel isnt an option, because the function isnt applicable to all of my Models, just 3 of them.

If possible I want to do it DRY.

To share methods between models in CakePHP use Behaviors (the model equivalent of controller components).

You can do something like this to define your custom validation rules:-

// app/Model/Behavior/ValidateBehavior.php
class ValidateBehavior extends ModelBehavior {
    public function customValidationRule($Model, $data) {
        // some validation code
    }
}

// example model
class Example extends AppModel {
    public $actsAs = array('Validate');

    public $validate = array(
        'field' => array(
            'custom' => array(
                'rule' => array('customValidationRule')
            )
        ),
    );
}