Swift 3 warning for dispatch async - ios

Question

I have this code:
DispatchQueue.global(priority: DispatchQueue.GlobalQueuePriority.default).async {
let url = URL(string: itemImageURL )
let data = try? Data(contentsOf: url!)
if data != nil {
DispatchQueue.main.async{
cell.advImage!.image = UIImage(data: data!)
}
}
}
I get this warning in Swift 3:
'default' was deprecated in iOS 8.0: Use qos attributes instead
on the first line.
Haven't found yet a solution. Has anybody?

Answer 1

try qos: DispatchQoS.QoSClass.default instead of priority: DispatchQueue.GlobalQueuePriority.default
DispatchQueue.global(qos: DispatchQoS.QoSClass.default).async {
let url = URL(string: itemImageURL )
let data = try? Data(contentsOf: url!)
if data != nil {
DispatchQueue.main.async{
cell.advImage!.image = UIImage(data: data!)
}
}
}

Answer 2

Instead of using priority parameter:
DispatchQueue.global(priority: DispatchQueue.GlobalQueuePriority.default).async {
// ...
}
use qos parameter that uses a different enum DispatchQoS.QoSClass.default but you can also use its enum value as just .default:
DispatchQueue.global(qos: .default).async {
// ...
}
Swift 3 has brought many changes on GCD(Grand Central Dispatch).

Answer 3

If you're creating a property using the Dispatch Framework and updating the UI with some animation within a function it might look something like this.
let queue = DispatchQueue.global(qos: DispatchQoS.QoSClass.default)
// dispatch_after says that it will send this animation every nsec
queue.asyncAfter(deadline: when) {
DispatchQueue.main.async(execute: {
self.animate(withDuration: 0.5, animations: {
self.image.setWidth(35)
self.image.setHeight(35)
})
})
}

Answer 4

Below code is tested for Swift 3.0 on Xcode 8.2.1
DispatchQueue.global(qos: .background).async {
let img2 = Downloader.downloadImageWithURL(imageURLs[1])
// Background Thread
DispatchQueue.main.async {
// Run UI Updates
self.imageView2.image = img2
}
}
where property of QoS are :
background, utility, `default`, userInitiated, userInteractive and unspecified
Refer this apple document for more details.