Bug? Form Validation and fields with brackets

Hi,

i have a textfield and radiobutton with [] in the name to validate.

The rules are

PHP Code:

public $group1 = [
        'textfield.*' => [
            'label' => '...',
            'rules' => 'required'
        ],
    ];

public $group2 = [
        'radiobutton.*' => [
            'label' => '...',
            'rules' => 'required'
        ],
    ]; 


Via getErrors() i can see the generated error messages. For the textfield the key in the array is transformed to textfield.0 but for the radiobutton the key is still radiobutton.*. Under my radiobutton in the template there is no output of the message:

PHP Code:

showError('textfield.' . $i) // is working
showError('radiobutton.' . $i) // is not working 


Is this a bug? Otherwise how can i get the correct key -> radiobutton.0 instead of radiobutton.*?