Cakephp 2.0 Localization for Model Messages - cakephp

Question

I am trying to get i18n to extract the strings from my model in Cakephp 2.0
The documentation states that
"CakePHP will automatically assume that all model validation error messages in your $validate array are intended to be localized. When running the i18n shell these strings will also be extracted."
http://book.cakephp.org/2.0/en/core-libraries/internationalization-and-localization.html
But my messages in my model are not being extracted into my po file when I run cake i18n and extract the data.
Does anyone know how to get the message strings into the po file?
App::uses('AuthComponent', 'Controller/Component');
class User extends AppModel {
public $validate = array(
'username' => array(
'required' => array(
'rule' => array('notEmpty'),
'message' => 'A Username is required',
'rule' => 'isUnique',
'message' => 'This username has already been taken'
)
);
}

Answer 1

This is how you can solve the problem I came across.
App::uses('AuthComponent', 'Controller/Component');
class User extends AppModel {
function __construct() {
parent::__construct();
$this->validate = array(
'username' => array(
'required' => array(
'rule' => array('notEmpty'))
'message' => __('A Username is required', true)),
'unique' => array(
'rule' => 'isUnique',
'message' => _('This username has already been taken', true)
)
);}
}

Answer 2

The correct way of achieve this is:
class AppModel extends Model {
public $validationDomain = 'validation_errors';
.
.
.
}
internally cake will call:
__d('validation_errors', 'Username should be more fun bla bla');
http://book.cakephp.org/2.0/en/console-and-shells/i18n-shell.html#model-validation-messages
http://book.cakephp.org/2.0/en/core-libraries/internationalization-and-localization.html#translating-model-validation-errors

Answer 3

Your $validate structure is a little messed up, you have two identical array keys (rule,message) under the required key. It should be:
public $validate = array(
'username' => array(
'required' => array(
'rule' => array('notEmpty'),
'message' => __('A Username is required', true),
),
'unique'=>array(
'rule' => 'isUnique',
'message' => __('This username has already been taken', true)
)
)
);