laravel 多对多关联删除中间表

// 多对多关系定义
public function adminUsers()
    {
        // 中间表
        $pivotTable = 'activity_admin_users';
        // 关联模型类名
        $relatedModel = AdminUser::class;

        // withTimestamps()自动更新时间戳
        return $this->belongsToMany($relatedModel, $pivotTable, 'activity_id', 'admin_user_id')->withTimestamps();
    }

    public static function boot()
    {
        parent::boot();

        static::deleting(function ($activity) {
            $activity->adminusers()->detach();
        });
    }