Yii2 Select2 - update -连接表上的选定值(多对多)

use kartik\select2\Select2;
use yii\helpers\ArrayHelper;

echo $form->field($model, 'attribute')->widget(Select2::classname(), [
    'data' => ArrayHelper::map($relatedModel::find()->all(), 'id', 'name'),
    'options' => ['placeholder' => 'Select a value ...'],
    'pluginOptions' => [
        'allowClear' => true,
        'multiple' => true,
    ],
]);

public function actionUpdate($id)
{
    $model = $this->findModel($id);

    if ($model->load(Yii::$app->request->post()) && $model->save()) {
        // 更新连接表的选定值
        $model->relatedModels = Yii::$app->request->post('Model')['attribute'];

        // 保存模型
        if ($model->saveRelatedModels()) {
            return $this->redirect(['view', 'id' => $model->id]);
        }
    }

    return $this->render('update', [
        'model' => $model,
    ]);
}