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Swift async/await demonstration
import UIKit
import _Concurrency
class SendSelectedPhotoWithEmailViewController: UIViewController {
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
// self.startFlow_PoD()
self.startFlow_AsyncAwait()
}
func startFlow_PoD() {
PhotosAPI.grantPhotosAccess { didGrantAccess in
if didGrantAccess {
PhotosAPI.selectPhoto { selectedPhoto in
NetworkAPI.upload(image: selectedPhoto) { uploadedFileUrl in
NetworkAPI.sendUrlWithEmail(urlString: uploadedFileUrl) { [weak self] didSend in
self?.displayResultAlert(didSendEmail: didSend)
}
}
}
}
}
}
@asyncHandler func startFlow_AsyncAwait() {
guard await PhotosAPI.grantPhotosAccess() else { return }
let selectedPhoto = await PhotosAPI.selectPhoto()
let uploadedFileUrl = await NetworkAPI.upload(image: selectedPhoto)
let didSendUrlWithEmail = await NetworkAPI.sendUrlWithEmail(urlString: uploadedFileUrl)
self.displayResultAlert(didSendEmail: didSendUrlWithEmail)
}
private func displayResultAlert(didSendEmail: Bool) {
// Display alert to the user
}
}
class PhotosAPI {
// MARK: Old PhotosAPI code (closures)
static func grantPhotosAccess(completion: @escaping (Bool) -> Void) {
DispatchQueue.main.async {
sleep(1) // Fake wait
completion(true)
}
}
static func selectPhoto(completion: @escaping (UIImage) -> Void) {
DispatchQueue.main.async {
sleep(1) // Fake wait
completion(UIImage())
}
}
// MARK: New PhotosAPI code (async/await)
static func grantPhotosAccess() async -> Bool {
await withUnsafeContinuation { continuation in
DispatchQueue.main.async {
sleep(1) // Fake wait
continuation.resume(returning: true)
}
}
}
static func selectPhoto() async -> UIImage {
await withUnsafeContinuation { continuation in
DispatchQueue.main.async {
sleep(1) // Fake wait
continuation.resume(returning: UIImage())
}
}
}
}
class NetworkAPI {
// MARK: Old NetworkAPI code (closures)
static func sendUrlWithEmail(urlString: String, completion: @escaping (Bool) -> Void) {
DispatchQueue.main.async {
sleep(1) // Fake wait
completion(true)
}
}
static func upload(image: UIImage, completion: @escaping (String) -> Void) {
DispatchQueue.main.async {
sleep(1) // Fake wait
completion("fake URL")
}
}
// MARK: New NetworkAPI code (async/await)
static func sendUrlWithEmail(urlString: String) async -> Bool {
await withUnsafeContinuation { continuation in
DispatchQueue.main.async {
sleep(1) // Fake wait
continuation.resume(returning: true)
}
}
}
static func upload(image: UIImage) async -> String {
await withUnsafeContinuation { continuation in
DispatchQueue.main.async {
sleep(1) // Fake wait
continuation.resume(returning: "fake URL")
}
}
}
}
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