Swift 3 warning for dispatch async

Question

I have this code:

DispatchQueue.global(priority: DispatchQueue.GlobalQueuePriority.default).async {
                let url = URL(string: itemImageURL )
                 


        

Answer 1

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.