iOS Concurrency with GCD & Operations

Sep 12 2023 · Swift 5.8, macOS 13, iOS 16, Xcode 14.3

Part 1: Grand Central Dispatch

05. Challenge: A Better Way to Download Images

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Previous episode: 04. Use Dispatch Work Items Next episode: 06. The Right Way to Download Images

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Challenge: A Better Way to Download Images

In the first episode, I showed you the sample app for this course. It’s unresponsive to user interaction because the image downloads all happen on the main thread, which should only be used for user interface tasks.

[weak self] in
  guard let self else { return }
store.downloadImageOffMainQueue(index:  // change On to Off .utility).async { 
} .utility).async { [weak self] in
  guard let self else { return }
if let data = try? Data(contentsOf: self.images[index].url),
  let decodedImage = UIImage(data: data) {
  images[index].image = decodedImage
DispatchQueue.main.async {
  self.images[index].image = decodedImage