here is is what i have in view/post/admin.php
<?php $this->widget('zii.widgets.grid.CGridView', array(
    'id'=>'post-grid',
    'dataProvider'=>$model->search(),
    'filter'=>$model,
    'columns'=>array(
        'id',
        'title',
        'content',
        'tags',
        array(
            'name'=>'status',
            'value'=>'Lookup::item("PostStatus",$data->status)',
            'filter'=>Lookup::items('PostStatus'),
        ),
        'create_time',
        'author_id',
        array(
            'class'=>'CButtonColumn',
        ),
    ),
)); ?>


and i replaced 'author_id' with ,
        array(
            'name'=>'author_id',
            'value'=>Lookup::usernme($model->author->id),
            )

by writing a function in lookup class like this,

 public static function usernme($userid)
    {

     $name = User::model()->findByPk($userid);
     $nme = $name->username;

     return $nme;

    }



i tried with array('name'=>'author_id', 'value'=>$model->author->username) which didnt worked 4 me