Revision control
Copy as Markdown
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
import UIKit
import Combine
public class ImageLoader {
private let cachedImages = NSCache<NSURL, UIImage>()
private var runningRequests = [UUID: URLSessionDataTask]()
private init() {}
public static let shared = ImageLoader()
}
public extension ImageLoader {
enum Error: Swift.Error {
case missingImage
}
@discardableResult
func loadImage(_ url: URL, _ completion: @escaping (Swift.Result<UIImage, Swift.Error>) -> Void) -> UUID? {
if let image = cachedImages.object(forKey: url as NSURL) {
completion(.success(image))
return nil
}
let uuid = UUID()
var request = URLRequest(url: url)
request.timeoutInterval = 3
let task = URLSession.shared.dataTask(with: request) { [weak self] data, response, error in
guard let self = self else { return }
defer { self.runningRequests.removeValue(forKey: uuid) }
if let error = error {
completion(.failure(error))
return
}
if let httpResponse = response as? HTTPURLResponse,
httpResponse.statusCode == 200,
let data = data,
let image = UIImage(data: data) {
self.cachedImages.setObject(image, forKey: url as NSURL)
completion(.success(image))
return
} else {
completion(.failure(Error.missingImage))
return
}
}
task.resume()
runningRequests[uuid] = task
return uuid
}
func loadImage(_ url: URL) -> Future<UIImage, Swift.Error> {
Future { [weak self] promise in
guard let self = self else { return }
self.loadImage(url) { result in
promise(result)
}
}
}
func cancelLoad(_ uuid: UUID) {
runningRequests[uuid]?.cancel()
runningRequests.removeValue(forKey: uuid)
}
}
public extension ImageLoader {
func load(_ url: URL) async throws -> UIImage {
return try await withCheckedThrowingContinuation { continuation in
loadImage(url) { result in
continuation.resume(with: result)
}
}
}
}