确定 id 是字符串类型， 然后试下这样:

 $model->id = new \yii\db\Expression('uuid()');

在ActiveRecord::behaviors()里增加一个PrimaryKeyBehavior来处理ActiveRecord::EVENT_BEFORE_INSERT这种方法可行

 class PrimaryKeyBehavior extends AttributeBehavior
{
    public $primaryKeyAttribute = 'id';

    public $value;

    public function init()
    {
        parent::init();

        if (empty($this->attributes)) {
            $this->attributes = [
                BaseActiveRecord::EVENT_BEFORE_INSERT => [$this->primaryKeyAttribute],
            ];
        }
    }

    protected function getValue($event)
    {
        return new Expression('UUID()');
    }

}

在model里调用

 class Test extends \yii\db\ActiveRecord
{
    ...
    public function behaviors()
    {
        return [
            \common\behaviors\PrimaryKeyBehavior::className(),
        ];
    }
    ...
}

这种方法可以实现灵活调用，在有需要的Model里调用，并且不用在写逻辑的时候加上$model->id = uuid()