PHPickerViewControllerDelegate load item using async await

Question

I can't find much documented regarding the PHPickerViewControllerDelegate didFinishPicking function using async await and I'm not sure I understand how to use the NSItemProvider. Here is my delegate code:

    func picker( _ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult]){
    for result in results {
        Task {
            if result.itemProvider.hasItemConformingToTypeIdentifier(UTType.image.identifier) {
                do {
                    let url = try await result.itemProvider.loadItem(forTypeIdentifier: UTType.image.identifier) as! URL
                    print(url.description)
                    let data = try Data(contentsOf: url)
                    let image = UIImage(data: data)
                }
                catch {
                    print(error)
                }
            }
        }
    }
}

When used in the simulator the ItemProvider returns a URL but the data content of that URL is empty. How do I grab the image from the ItemProvider? Thanks

If you want the data then I would use loadDataRepresentation instead of loadItem. — HangarRash
– HangarRash, Commented Mar 1, 2023 at 22:18
loadDataRepresentation is not available with async/await which I would prefer. What exactly does loadItem return? I don't necessarily need data, just the image and (if possible) metadata. — David
– David, Commented Mar 3, 2023 at 18:59
It's a shame only loadItem comes in the async form. To me that's the least clear method since there's no way to know what it's going to return. — HangarRash
– HangarRash, Commented Mar 3, 2023 at 19:34

matt · Accepted Answer · 2024-11-13 15:26:56Z

As you've been told in a comment, it's a much better idea to use loadDataRepresentation here. As you've said, there is no async version of loadDataRepresentation — but you can write one by extending NSItemProvider:

import Foundation
import UniformTypeIdentifiers

extension NSItemProvider {
    /// Injected method that abstracts image data loading and makes it async/await.
    /// - Returns: The data.
    func loadImageData() async throws -> Data {
        enum ImageLoadingError: Error {
            case unknown
        }
        return try await withCheckedThrowingContinuation { continuation in
            self.loadDataRepresentation(forTypeIdentifier: UTType.image.identifier) { data, error in
                if let data {
                    continuation.resume(returning: data)
                } else {
                    continuation.resume(throwing: error ?? ImageLoadingError.unknown)
                }
            }
        }
    }
}

Now your PHPickerViewControllerDelegate method can call that, like this:

func picker(_ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult]) {
    picker.dismiss(animated: true) {
        Task { @MainActor in
            guard let result = results.first else { return }
            let provider = result.itemProvider
            let data = try await provider.loadImageData()
            // do something with the data here
        }
    }
}

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