Modern Concurrency: Getting Started

Oct 18 2022 Swift 5.5, iOS 15, Xcode 13.4

Part 2: Asynchronous Sequences

11. Using Asynchronous Methods in Views

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Previous episode: 10. Concurrency With async let Next episode: 12. Displaying a Progress View

This video Using Asynchronous Methods in Views was last updated on Oct 18 2022

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SuperStorage app

The download view downloads the file using your choice of subscription plan: silver, gold or Cloud 9.

Download data

In SuperStorageModel, locate download(file:). It already contains the code you know so well:

guard let url = URL(
string: "http://localhost:8080/files/download?\(file.name)") else {
  throw "Could not create the URL."
}
let (data, response) = try await URLSession.shared.data(from: url)
guard (response as? HTTPURLResponse)?.statusCode == 200 else {
  throw "The server responded with an error."
}

addDownload(name: file.name)

updateDownload(name: file.name, progress: 1.0)

return data

Call download(file:)

Now, where do you call this asynchronous method? Open DownloadView. Go to its body.

fileData = try await model.download(file: file)

let downloadSingleAction: ()  🟩async🟥 -> Void

Task {
  fileData = try await model.download(file: file)
}

@MainActor 
func addDownload(name: String) { ... }
@MainActor 
func updateDownload(name: String, progress: Double) { ... }

.onDisappear {
  fileData = nil
  model.reset()
}