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Ios swift – Strict concurrency and Swift 6 produces error when trying to convert PhotosPickerItem to Data

I have the below view where I want to load an image from gallery using PhotosPicker and display it to the user. I also want to convert the image to Data so I can store it in SwiftData database.

After updating to iOS 18, xcode 16.0 beta and changing strict concurrency from minimal to complete and swift version from 5 to 6, I receive the error Sending main actor-isolated value of type 'PhotosPickerItem' with later accesses to nonisolated context risks causing data races on line if let data = try? await selectedPhoto?.loadTransferable(type: Data.self).

I had many more errors but I managed to get rid of them. The app is working as expected, but I have no idea how to solve this error.

Any help would be really appreciated.

Note: for simplicity, I removed all other properties of Model from the code below.

struct AddModel: View {
    
    @Environment(ViewModel.self) private var viewModel
    @Environment(.dismiss) private var dismiss
    
    @State private var showPhotosPicker: Bool = false
    
    @State private var selectedPhoto: PhotosPickerItem?
    @State private var selectedPhotoData: Data?
    
    var body: some View {
        Form {
            photoSection
        }
        .toolbar {
            toolbarItems
        }
    }
}

// MARK: - View Components

extension AddShoeView {
    
    @ViewBuilder
    private var photoSection: some View {
        Section {
            VStack(spacing: 12) {
                ZStack {
                    if let selectedPhotoData, let uiImage = UIImage(data: selectedPhotoData) {
                        Image(uiImage: uiImage)
                            .resizable()
                            .scaledToFill()
                            .frame(width: 150, height: 150)
                            .clipShape(RoundedRectangle(cornerRadius: 12))
                    } else {
                        Image(systemName: "square.fill")
                            .resizable()
                            .foregroundStyle(.secondary)
                            .frame(width: 150, height: 150)
                            .clipShape(RoundedRectangle(cornerRadius: 12))
                    }
                }
                
                Text("Add Photo")
                    .font(.callout)
                    .fontWeight(.semibold)
                    .foregroundStyle(.white)
                    .padding(.horizontal, 12)
                    .padding(.vertical, 8)
                    .background(Color(uiColor: .secondarySystemBackground))
                    .cornerRadius(20)
            }
            .frame(maxWidth: .infinity)
            .photosPicker(isPresented: $showPhotosPicker, selection: $selectedPhoto, photoLibrary: .shared())
            .onTapGesture {
                showPhotosPicker.toggle()
            }
            .task(id: selectedPhoto) {
                if let data = try? await selectedPhoto?.loadTransferable(type: Data.self) {
                    selectedPhotoData = data
                }
            }
        }
        .listRowBackground(Color.clear)
        .listRowInsets(EdgeInsets())
    }
    
    
    @ToolbarContentBuilder
    private var toolbarItems: some ToolbarContent {
        ToolbarItem(placement: .confirmationAction) {
            Button {
                viewiewModel.addModel(image: selectedPhotoData)
                dismiss()
            } label: {
                Text("Save")
            }
        }
    }
}

@Observable
final class ViewModel: {
    
    @ObservationIgnored private var modelContext: ModelContext
    
    private(set) var models: [Model] = []
    
    init(modelContext: ModelContext) {
        self.modelContext = modelContext
        fetchModels()
    }
        
    func addModel(image: Data?) {
        let model = Model(image: image)

        modelContext.insert(shoe)
        
        save()
    }

    private func fetchModels() {
        do {
            let descriptor = FetchDescriptor<Model>()
            self.models = try modelContext.fetch(descriptor)
        } catch {
            print("Fetching shoes failed, (error.localizedDescription)")
        }        
    }

    private func save() {
        do {
            try modelContext.save()
        } catch {
            print("Saving context failed, (error.localizedDescription)")
        }
        
        fetchModels()
    }
}
Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    As a solution I found this code working really well. Not sure if this is the right approach, but for now it is good enough for me.

    First of all, I created a AddItemViewModel to hold the selectedPhoto and selectedPhotoData and made this to conform to @unchecked Ssendable. My intention is somehow get rid of the @unchecked, but I still have a lot to learn.. :)

    @Observable
final class AddItemViewModel: @unchecked Sendable {

    var showPhotosPicker: Bool = false

    var selectedPhoto: PhotosPickerItem?
    var selectedPhotoData: Data?

    init(selectedPhoto: PhotosPickerItem? = nil, selectedPhotoData: Data? = nil) {
        self.selectedPhoto = selectedPhoto
        self.selectedPhotoData = selectedPhotoData
    }

    func loadPhoto() async {
        if let data = try? await selectedPhoto?.loadTransferable(type: Data.self) {
            await MainActor.run {
                selectedPhotoData = data
            }
        }
    }
}

    Create a @State private var vm = AddViewModel() inside the AddModel view and use its properties instead of the AddModel view properties.

    Also make the original ViewModel conform to @unchecked Sendable and fix the remaining errors related to the AddModel view properties not being available anymore and use those from the newly created AddItemViewModel instead.

    For now I am not gonna accept my answer, so everyone seeing this, I hope you'll find a better and more professional solution. :)


  2. 0

    Try using Task.detached to wrap loadTransferable? In Xcode 16 the whole SwiftUI view is decorated by @MainActor, so the task function and Task inside is running on MainActor, which may not be expected.

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