Image from XML to Cell - image

Question

i wanted to load ASYNC an Image to a Cell.
my Code is:
override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("Cell") as xmlParserDatenCell
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
var test = UIImage(data: NSData(contentsOfURL: NSURL(string: daten[imagePath.row]["bildlink"]!)!)!)
cell.bild1.image = test
})
my answer from this is nil.
No idea to to it. :(
i searched the WEB for hrs.
EDIT:
var daten = [String:String] looks my daten.
and my parser returns this into:
daten.append(String:String)

Answer 1

There are a lot of things going wrong here. When you leave the main queue for an async, you have to return to main before setting the image. Additionally, you need to debug your code to make sure at each step you're getting what you expect (i.e. Is daten[0]["bildlink"] actually returning an image address?)
Anyways, here's some code that should work if you're using swift 1.2 and the xml is actually returning some data.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) { () -> Void in // background
var loadedImage: UIImage? //optional image, will be set if the rest succeeds
if let link = daten[indexPath.row]["bildlink"], // address for image
url = NSURL(string: link), // .. to URL
data = NSData(contentsOfURL: url), // .. to data
image = UIImage(data: data) { // .. image from data
loadedImage = image
}
dispatch_async(dispatch_get_main_queue()) { () -> Void in // return to main thread
cell.bild1.image = loadedImage ?? nil // if above successful, actually set image
}
}
You should also check to make sure the cell hasn't been reused before setting the image. You can do this a whole bunch of ways, but I would add a property like imageAddress to save the string from daten[0]["bildlink"] and reference it like if cell.imageAddress == link { cell.bild1.image = loadedImage }

Answer 2

To make an async web request you can use:
NSURLConnection.sendAsynchronousRequest(urlRequest, queue: NSOperationQueue(), completionHandler:{
(response:NSURLResponse!, data: NSData!, error: NSError!) -> Void in
// do stuff with response, data & error here
})
If you're using it inside of cellForRowAtIndexPath:, you may not end up with the same cell as you expect since it's async and cells get reused, so make sure you have the correct cell before you set the image:
func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
var cell = self.tableView!.dequeueReusableCellWithIdentifier("Cell") as UITableViewCell
var urlRequest = NSMutableURLRequest(URL: NSURL(string: daten[indexPath.row]["bildlink"]!)!)
NSURLConnection.sendAsynchronousRequest(urlRequest, queue: NSOperationQueue(), completionHandler:{
(response:NSURLResponse!, data: NSData!, error: NSError!) -> Void in
if let cellToUpdate = self.tableView?.cellForRowAtIndexPath(indexPath) {
cellToUpdate.imageView?.image = UIImage(data: data)
// need to reload the view, which won't happen otherwise since this is in an async call
cellToUpdate.setNeedsLayout()
}
})
}