Radiobuttonlist Submit Value To A Different Model

I have a model A which has a belonging relation with B

so i use $model->fkB->attribB to get any value of its column

In Textfield i take value from my update form as

<?php echo $form->textField($modelA,‘attribB’,array(‘size’=>60,‘maxlength’=>255 ,‘value’=>$model->fkB->attribB )); ?>

Doing this , i get the value of attribB on the textbox , and when the form submits i recieve it in modelA …

I want to do the same in radioButtonList but the radioButtonList doesnot work the similar way and ends up in Exception

"Property "A.attribB" is not defined. "

Could you please share your code for RadioButtonlist.