How to process data from multiple results with enum - ios

Question

I want to get a UIImage and title from my object so I make a generic result with enum.
but I have an error while I try to take my result in completionHandler and an error while I called my func fetchDataResult(for video: Video, completion: #escaping (Results<(UIImage?, String?)>) -> ()) in my controller. This is my code.
Member 'success' in 'Results<(UIImage?, String?)>' produces result of type 'Results', but context expects 'Results<(UIImage?, String?)>'
enum Results<Value> {
case success(Value)
case failure(Error)
}
class VideoStore {
func fetchDataResult(for video: Video, completion: #escaping (Results<(UIImage?, String?)>) -> ()) {
guard let videoKey = video.videoID else {
preconditionFailure("Video expected to have a video id")
}
if let image = imageStore.image(forKey: videoKey) {
OperationQueue.main.addOperation {
completion(.success((image, nil)))
}
return
}
guard let videoURL = video.url else {
preconditionFailure("Video expected to have video url")
}
if let videoTitle = video.title {
OperationQueue.main.addOperation {
completion(.success((nil, videoTitle)))
}
}
let request = URLRequest(url: videoURL)
let task = sessions.dataTask(with: request) { (data, response, error) in
let result = self.processDataRequest(data: data, error: error)
if case let .success(image) = result {
self.imageStore.setImage(image, forKey: videoKey)
}
OperationQueue.main.addOperation {
completion(.success((result, nil)))
}
}
task.resume()
}
private func processDataRequest(data: Data?, error: Error?) -> Results<UIImage> {
guard
let imageData = data,
let image = UIImage(data: imageData) else {
if data == nil {
return .failure(error!)
} else {
return .failure(ThumbnailError.thumbnailCreationError)
}
}
return .success(image)
}
}
This is my VideoController that have an error
Cannot assign value of type '(UIImage?, String?)' to type 'UIImage?'
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
let video = videoDataSource.videos[indexPath.row]
videoStore.fetchDataResult(for: video) { (results) in
guard
let videoIndex = self.videoDataSource.videos.firstIndex(of: video),
case let .success(image) = results else { return }
let photoIndexPath = IndexPath(item: videoIndex, section: 0)
if let cell = tableView.cellForRow(at: photoIndexPath) as? VideoCell {
cell.videoImgView.image = image
}
}
}

Answer 1

The results in the following line:
videoStore.fetchDataResult(for: video) { (results) in
has a type (UIImage?, String?).
The completion handler for your fetchDataResult gets the type Results<(UIImage?, String?)> as you defined, which makes the case success(Value) to case success((UIImage?, String?)).
If you only need UIImage? from the value, you need to do
guard
let videoIndex = self.videoDataSource.videos.firstIndex(of: video),
case let .success(image, _) = results else { return }
Note that Swift has its own Results type since Swift 5.