Cell repopulating over each other in TableView - swift

Question

I'm currently working with a tableview that contains three sections. Each section loads it's data from an array that is loaded from a backend and is stored in a local array. The data downloads and displays without issue, but once I scroll, the cells reload themselves over their previous data. The reason I caught it, outside of the memory warning, was that the cell contains an image with a drop shadow and the shadow grows darker with each scroll. I have a feeling the issue is related to how I'm calling the cell at indexPath for each section but can't seem to find a solution. I've searched around and haven't been able to find a resolution yet.
The cells all share the same custom class and reload their respective data through the same outlets.
Not sure if this is relevant to the issue but the view is called from information in the AppDelegate.
Here's the code that I'm working with staring with number of rows in section.
override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if section == 0 {
return likesName.count
} else if section == 1 {
return commentsName.count
} else if section == 2 {
return bookmarksName.count
}
return 1
}
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = UITableViewCell()
if indexPath.section == 0 {
let cell = tableView.dequeueReusableCellWithIdentifier("toggleCell", forIndexPath:indexPath) as! RightToggleCell
cell.userAvatar.layer.cornerRadius = cell.userAvatar.frame.size.width/2
cell.userAvatar.clipsToBounds = true
cell.artworkImage.contentMode = UIViewContentMode.ScaleAspectFill
cell.artworkImage.clipsToBounds = true
cell.artistName.text = likesName[indexPath.row]
cell.information.text = "liked your artwork"
likesImage[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in
if let downloadedImage = UIImage(data: data!) {
cell.artworkImage.image = downloadedImage
}
}
likesAvatar[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in
if let downloadedImage = UIImage(data: data!) {
cell.userAvatar.image = downloadedImage
}
}
} else if indexPath.section == 1 {
let cell = tableView.dequeueReusableCellWithIdentifier("toggleCell", forIndexPath:indexPath) as! RightToggleCell
cell.userAvatar.layer.cornerRadius = cell.userAvatar.frame.size.width/2
cell.userAvatar.clipsToBounds = true
cell.artworkImage.contentMode = UIViewContentMode.ScaleAspectFill
cell.artworkImage.clipsToBounds = true
cell.artistName.text = commentsName[indexPath.row]
cell.information.text = commentsInformation[indexPath.row]
commentsImage[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in
if let downloadedImage = UIImage(data: data!) {
cell.artworkImage.image = downloadedImage
}
}
commentsAvatar[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in
if let downloadedImage = UIImage(data: data!) {
cell.userAvatar.image = downloadedImage
}
}
} else if indexPath.section == 2 {
let cell = tableView.dequeueReusableCellWithIdentifier("toggleCell", forIndexPath:indexPath) as! RightToggleCell
cell.userAvatar.layer.cornerRadius = cell.userAvatar.frame.size.width/2
cell.userAvatar.clipsToBounds = true
cell.artworkImage.contentMode = UIViewContentMode.ScaleAspectFill
cell.artworkImage.clipsToBounds = true
cell.artistName.text = bookmarksName[indexPath.row]
cell.information.text = "bookmarked your artwork"
bookmarksImage[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in
if let downloadedImage = UIImage(data: data!) {
cell.artworkImage.image = downloadedImage
}
}
bookmarksAvatar[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in
if let downloadedImage = UIImage(data: data!) {
cell.userAvatar.image = downloadedImage
}
}
}
return cell
}

Answer 1

It's a bit hard to line up your code, but it looks like you have:
let cell = ...
if ... {
let cell = ...
} else if ... {
let cell = ...
}
return cell
If this is what you have, the let cell inside each if is only scoped to exist within that if. Therefore, the return cell at the end will return the initial, empty cell. If this is the case, you should change it to:
if ... {
let cell = ...
return cell
} else if ... {
let cell = ...
return cell
} else {
let cell = ...
return cell
}
Note that the last condition must just be else and not else if or the compiler will tell you not all code paths return a value (when the last "if" fails). However, you're saying it's basically working, so something doesn't make sense.
Either way, cells get reused for new rows once a row moves off screen. Therefore, by the time your getDataInBackgroundWithBlock returns, the cell might belong to a different row. Given the drop-shadow is getting darker, it sounds like you have code in RightToggleCell that is rerunning when a cell gets reused.
When you load data in the background, you should store it outside the cell, and reload that row when the load finishes. Something (very roughly) along the lines of:
likesImage[indexPath.row].getDataInBackgroundWithBlock { (data, error) -> Void in
if let downloadedImage = UIImage(data: data!) {
artworkImages[indexPath.row] = downloadedImage
dispatch_async(dispatch_get_main_queue(), {
tableView.reloadRowsAtIndexPaths([indexPath.row], withRowAnimation: true)
})
}
}
The cellForRowAtIndexPath should display the relevant artworkImages if it's available, or use the above code if not. Note that any updating of the UI must be done on the main thread, which is why dispatch_async is being called above.

Answer 2

Instead of doing everything on the TableViewController i suggest you to put this code into your "RightToggleCell".
override func awakeFromNib() {
self.userAvatar.layer.cornerRadius = self.userAvatar.frame.size.width/2
self.userAvatar.clipsToBounds = true
self.artworkImage.contentMode = UIViewContentMode.ScaleAspectFill
self.artworkImage.clipsToBounds = true
}
By doing this iOS doesn't modify cornerRadius and clipsToBounds everytime you reload your TableView

Answer 3

With the guidance from Michael, I moved return cell inside of each if let statement and returned UITableViewCell() outside of the statements and that resolved the issue. Thanks again Michael, I up voted your response but I don't have a high enough reputation for it to post.