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May 8, 2024 21:37
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ResourceCacheTest.swift
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| // | |
| // ResourceCacheTest.swift | |
| // Test (iOS) | |
| // | |
| // Created by Malcolm Hall on 08/05/2024. | |
| // | |
| import SwiftUI | |
| import AsyncAlgorithms | |
| struct ResourceCacheTest { | |
| struct RuntimeError: LocalizedError { | |
| let description: String | |
| init(_ description: String) { | |
| self.description = description | |
| } | |
| var errorDescription: String? { | |
| description | |
| } | |
| } | |
| @MainActor | |
| class ResourceCache { | |
| enum Request { | |
| case inprogress | |
| case success(UIImage) | |
| case failed(Error) | |
| } | |
| let urls: AsyncChannel<URL> | |
| var requests: [AsyncChannel<(URL, Request)>] = [] | |
| init() { | |
| let urls = AsyncChannel<URL>() | |
| self.urls = urls | |
| Task { | |
| var requestsByURL: [URL : Request] = [:] | |
| for await url in urls { | |
| print("loop") | |
| try? await Task.sleep(for: .seconds(1)) // testing | |
| print("url \(url)") | |
| if let request = requestsByURL[url] { | |
| switch request { | |
| case .inprogress: | |
| continue | |
| default: | |
| for channel in requests { | |
| await channel.send((url, request)) | |
| } | |
| } | |
| } | |
| var request: Request = .inprogress | |
| requestsByURL[url] = request | |
| let urlRequest = URLRequest(url: url) | |
| do { | |
| print("requesting...") | |
| let (data, _) = try await URLSession.shared.data(for: urlRequest) | |
| let image = UIImage(data: data)! | |
| request = .success(image) | |
| } catch { | |
| print("Failed to fetch resource:", error) | |
| request = .failed(error) | |
| } | |
| requestsByURL[url] = request | |
| for channel in requests { | |
| await channel.send((url, request)) | |
| } | |
| } | |
| } | |
| } | |
| } | |
| struct MyView: View { | |
| let resourceCache: ResourceCache | |
| @State var image: UIImage? | |
| let text: String | |
| let url: URL | |
| var body: some View { | |
| Group { | |
| if let image { | |
| Image(uiImage: image) | |
| } | |
| else { | |
| Text("Loading") | |
| .task { | |
| await withDiscardingTaskGroup { group in | |
| group.addTask { @MainActor in | |
| let requests = AsyncChannel<(URL, ResourceCache.Request)>() | |
| resourceCache.requests.append(requests) | |
| for await (_, request) in requests.filter({ url, request in | |
| url == self.url | |
| }) { | |
| switch request { | |
| case .success(let image): | |
| self.image = image | |
| default: | |
| break | |
| } | |
| } | |
| resourceCache.requests.removeAll { requests === $0 } | |
| } | |
| print("sending \(text)") | |
| await resourceCache.urls.send(url) | |
| print("sent \(text)") | |
| } | |
| } | |
| } | |
| } | |
| } | |
| } | |
| struct ContentView: View { | |
| @State var resourceCache: ResourceCache? | |
| var body: some View { | |
| if let resourceCache { | |
| VStack { | |
| MyView(resourceCache: resourceCache, text: "1", url: URL(string: "https://avatars.githubusercontent.com/u/61242156?s=100&v=4")!) | |
| MyView(resourceCache: resourceCache, text: "2", url: URL(string: "https://avatars.githubusercontent.com/u/31996?s=100&v=4")!) | |
| MyView(resourceCache: resourceCache, text: "3", url: URL(string: "https://avatars.githubusercontent.com/u/61242156?s=100&v=4")!) | |
| } | |
| }else { | |
| Text("Initialising...") | |
| .onAppear { | |
| resourceCache = ResourceCache() | |
| } | |
| } | |
| } | |
| } | |
| } |
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