Repeating images when scrolling in UITableView Swift - ios

Question

EDITED CODE FROM BELOW ANSWER
WHAT I WANT
The images are correct size and show in the correct positions
WHAT I GET
A bunch of images showing up everywhere randomly when I scroll
I have looked through so many answers and I still haven't found a solution to my problem. It seems quite often it is a different problem for each person, and it doesn't help that most questions here are in Objective-C. I find it difficult converting from one to another.
I will just show my table view functions and explain my code and maybe somebody can identify the problem or help me to identify to solve it myself.
-----------------------------------------------------------------------------------
Explanation
Not all News Items (cells) contain pictures. So as you can see (in the first function below) I loop through the sections and the nested cells and if the news item contains a picture if newslists[i][j] != "None, I display the image. From this point it is familiar code, seen from the tutorial here
In the second function I once again loop through the sections and the cells till I land on one that should contain an image. I then change the height of this cell so the image will fit inside.
That is pretty much it...
any ideas?
-----------------------------------------------------------------------------------
CellForRowAtIndexPath
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("NewsCell", forIndexPath: indexPath) as! UITableViewCell
if newslists[indexPath.section][indexPath.row].imageURL != "None"{
let urlString = newslists[indexPath.section][indexPath.row].imageURL
let imgURL = NSURL(string: urlString)
cell.imageView?.image = UIImage(named: "first") // placeholder
if let img = imageCache[urlString] {
cell.imageView?.image = img
println("loaded from cache")
}
else {
let request: NSURLRequest = NSURLRequest(URL: imgURL!)
let mainQueue = NSOperationQueue.mainQueue()
NSURLConnection.sendAsynchronousRequest(request, queue: mainQueue, completionHandler: { (response, data, error) -> Void in
if error == nil {
let image = UIImage(data: data)
self.imageCache[urlString] = image
dispatch_async(dispatch_get_main_queue(), {
if let cellToUpdate = tableView.cellForRowAtIndexPath(indexPath) {
cellToUpdate.imageView?.image = image
println("succesfully downloaded image")
println("size of cache is \(self.imageCache.count)")
}
})
}
else {
println("Error: \(error.localizedDescription)")
}
})
}
}
cell.backgroundColor = UIColor(red: 52/255, green: 138/255, blue: 169/255, alpha: 1.0)
return cell
}
I have one more function that may be causing problems but I doubt it:
HeightForRowAtIndexPath
func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
if newslists[indexPath.section][indexPath.row].imageURL != "None"{
println("Expanding cell for \(indexPath.section) \(indexPath.row)")
return 190.0
}
return 70.0
}

Answer 1

I'm not sure why you have a double for loop in both method. There are called for every indexPath possible so you can just get you appropriate data with the indexPath section and row.
You can try this code, i don't see any reason for it to not work.
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("NewsCell", forIndexPath: indexPath) as! UITableViewCell
cell.imageView?.image = nil
if newslists[indexPath.section][indexPath.row].imageURL != "None"{
let urlString = newslists[indexPath.section][indexPath.row].imageURL
let imgURL = NSURL(string: urlString)
cell.imageView?.image = UIImage(named: "first") // placeholder
if let img = imageCache[urlString] {
cell.imageView?.image = img
println("loaded from cache")
}
else {
...
}
}
return cell
}
func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat {
if newslists[indexPath.section][indexPath.row].imageURL != "None"{
println("Expanding cell for \(i) \(j)")
return 190.0
}
return 70.0
}

Answer 2

All we need to do is use the prepareForReuse() function. As discussed in this medium article, This function is called before cell reuse, letting you cancel current requests and perform a reset.
override func prepareForReuse() {
super.prepareForReuse()
imageView.image = nil
}