Like button feature not working through parse - ios

Question

I'm trying to implement a like button function on my app, similar to facebook or instagram, through parse. I tried using this code below and it works. When the user taps the button on an object(or in my case messages), the like goes up by 1 point. However, when the user quits the app and launches it they can like the same object again, meaning they can like as many times as they want. Do I need to edit something in this code or try a whole different method?
#IBAction func likeButton(sender: UIButton) {
sender.enabled = false
sender.userInteractionEnabled = false
sender.alpha = 0.5
//get the point in the table view that corresponds to the button that was pressed
//in my case these were a bunch of cells each with their own like button
let hitPoint = sender.convertPoint(CGPointZero, toView: self.tableView)
let hitIndex = self.tableView.indexPathForRowAtPoint(hitPoint)
let object = objectAtIndexPath(hitIndex)
//this is where I incremented the key for the object
object!.incrementKey("count")
object!.saveInBackground()
self.tableView.reloadData()
NSLog("Top Index Path \(hitIndex?.row)")
}

Answer 1

Here is the way in which I would approach the problem:
First, I would make disabling the button into its own function like so:
func disableButton(button: UIButton){
button.enabled = false
button.userInteractionEnabled = false
button.alpha = 0.5
}
(And when the user presses the like button it is disabled like so:)
#IBAction func likeButton(sender: UIButton) {
disableButton(sender)
//get the point in the table view that corresponds to the button that was pressed
//in my case these were a bunch of cells each with their own like button
let hitPoint = sender.convertPoint(CGPointZero, toView: self.tableView)
let hitIndex = self.tableView.indexPathForRowAtPoint(hitPoint)
let object = objectAtIndexPath(hitIndex)
//this is where I incremented the key for the object
object!.incrementKey("count")
object!.saveInBackground()
self.tableView.reloadData()
NSLog("Top Index Path \(hitIndex?.row)")
}
Then I would make an attribute of users their liked posts, which is an array of strings of the objectIds of these posts. (Since users would probably end up liking many posts, you really should use relations, but arrays are easier to understand. The documentation for relationships between PFObjects is here.) Then, when creating the cell for each post, where cell is the cell you are creating, post is the current post in the list and cell.likeButton is the like button from the cell:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell{
let cell = YourCell()
let post = posts[indexPath.row]
if (PFUser.currentUser!["likedPosts"] as! [String]).contains(post.objectId){
cell.disableButton(cell.likeButton)
}
//Setup rest of cell