jamband

<?php $this->widget('zii.widgets.grid.CGridView', array(
    'id' => 'hoge-grid',
    'dataProvider' => $model->search(),
    'filter' => $model,
    'columns' => array(
        'id',
        array(
            'name' => 'username',
            'value' => '$data->user->username',
        ),

jamband

<?php
class Hoge extends CActiveRecord
{
    public $username; // 追加
    ...

    /**
     * @see CModel::rules()
     */
    public function rules()