情境要求：

要在订单（Order）视图的gridview中显示出客户（Customer）姓名，并使其具有与其它字段相同的排序和搜索功能。

数据库结构

订单表 orde r含有字段 customer_id 与 客户表 customer 的 id 字段关联

首先确保在 Order Model 中包含以下代码：

public function getCustomer()
{
    return $this->hasOne(Customer::className(), ['id' => 'customer_id']);
}

用gii会自动生成此代码；

第一步：在 OrderSearch 添加一个 $customer_name 变量

class OrderSearch extends Order
{
    public $customer_name; //<=====就是加在这里
}

第二步：修改 OrderSearch 中的 search 函数

public function search($params)
{
    $query =  Order::find();
    $query->joinWith(['customer']);<=====加入这句
    $dataProvider = new ActiveDataProvider([
        'query' => $query,
    ]);
    $dataProvider->setSort([
        'attributes' => [
            /* 其它字段不要动 */    
            /*  下面这段是加入的 */
            /*=============*/
            'customer_name' => [
                'asc' => ['customer.customer_name' => SORT_ASC],
                'desc' => ['customer.customer_name' => SORT_DESC],
                'label' => 'Customer Name'
            ],
            /*=============*/
        ]
    ]); 
    if (!($this->load($params) && $this->validate())) {
        return $dataProvider;
    }
    $query->andFilterWhere([
        'id' => $this->id,
        'user_id' => $this->user_id,
        'customer_id' => $this->customer_id,
        'order_time' => $this->order_time,
        'pay_time' => $this->pay_time,
    ]);
    $query->andFilterWhere(['like', 'status',  $this->status]);
     $query->andFilterWhere(['like', 'customer.customer_name', $this->customer_name]) ;//<=====加入这句
    return $dataProvider;
}

第三步： 修改 order/index 视图的gridview

// attribute 要在model里面设置好，如果直接写中文不能排序和搜索
<span class="redactor-invisible-space"><?= GridView::widget([ 
    'dataProvider' => $dataProvider,</span>
    'filterModel' => $searchModel,
    'columns' => [
        ['class' => 'yii\grid\SerialColumn'],
        'id',
        'customer_id',  
        'status',
        ['label'=>'客户',  'attribute' => 'customer_name',  'value' => 'customer.customer_name' ],//<=====加入这句
        ['class' => 'yii\grid\ActionColumn'],
    ],
]); 
?>