Question

我正在尝试为我的电影应用制作一些投票按钮。

我使用Parse，我创建了一个名为Votes_Up的新类。在本课程中，他们分为两列：User_Voting和Film_VotedFor。

按下按钮时，下面的代码会被执行。它将当前用户和电影对象按下按钮，然后将它们添加到Parse。我的数据库如下所示：

我需要什么

所以他们当前的工作方式，如果用户按下投票按钮，它会将信息添加到数据库并将计数加1。当用户再次按下它时，它只是通过取消1来更新计数。

我还想删除它已经添加到数据库中的行，由投票给它的用户删除。我怎么能这样做？

我的代码：

@IBAction func upVoteButton(sender: UIButton) {

    let hitPoint = sender.convertPoint(CGPointZero, toView: self.tableView)
    let hitIndex = self.tableView.indexPathForRowAtPoint(hitPoint)
    let object = objectAtIndexPath(hitIndex)

    if PFUser.currentUser() != nil {

        if userPressedUpButton == false {

            userPressedUpButton = true

            let voteUp = PFObject(className: "Votes_Up")
            voteUp["User_Voting"] = PFUser.currentUser()
            voteUp["Film_VotedFor"] = object!

            object!.incrementKey("UpVoteCount")
            object!.saveInBackground()

            voteUp.saveInBackgroundWithBlock({ (success, error) in

                if success == true {

                    // Object(s) was/were successfully saved

                } else if error != nil {

                    // Display an alert to the user

                } else {

                    // Display an alert to the user - something went wrong

                }

            })

        } else {

            userPressedUpButton = false

           // I need to removed the row from the class here that was added, as the user has retracted their vote!

            object!.incrementKey("UpVoteCount", byAmount: -1)
            object!.saveInBackground()

        }

    } else {

        // No user is logged in so they can't vote
        performSegueWithIdentifier("Votes_LoginPopup", sender: self)

    }

    self.tableView.reloadData()

}

Answer 1

试试这个：

var query = PFQuery(className:"Votes_Up")
    query.whereKey("User_Voting", equalTo:PFUser.currentUser())
    query.limit = 1
    query.findObjectsInBackgroundWithBlock {
        (votesUp: [AnyObject]?, error: NSError?) -> Void in
        if error == nil {
            if let objects = votesUp as? [PFObject] {
                var firstObject = objects[0]
                dispatch_async(dispatch_get_main_queue(),{
                    // do delete here
                    firstObject.deleteEventually();
                })

            }
        }
    }

或者这个：

let query = PFQuery(className: "Votes_Up")
query.whereKey("User_Voting", equalTo: PFUser.currentUser())
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]?, error: NSError?) -> Void in
    for object in objects {
        object.deleteEventually()
    }
}

在Parse - In Swift中从类中删除一行

1 个答案: