SwiftUI PhotosPicker - get the size of picked item in Kilobytes

var body: some View {
    
    PhotosPicker(selection: $selectedItem, matching: .any(of: [.images, .videos]), photoLibrary: .shared()){
        Image(systemName: "camera.fill")
            .resizable()
            .aspectRatio(contentMode: .fit)
            .frame(height: 20)
            .padding(2)

    }
    .onChange(of: selectedItem) { newItem in
        
        // item size in kilobytes?
    }
}

Is there a way to get the size of selectedItem in Kilobytes?

I know how to do it by finding out the URL of the item first and then the size of it by the URL, but this is kinda a dumb workaround since the item is already selected and it's also kinda slow.

You can load the item and use the byte count.

import SwiftUI
import PhotosUI
struct PhotoFileSize: View {
    @State private var selectedItem: PhotosPickerItem?
    
    var body: some View {
        PhotosPicker(selection: $selectedItem) {
            Text("Selected Item")
        }
        .task(id: selectedItem) {
            //Only run this code if there is a selected item
            guard let selectedItem else {return}
            
            do {
                let result = try await selectedItem.loadTransferable(type: Data.self)
                
                switch result {
                case .none:
                    break
                case .some(let data):
                    let size = Measurement(value: Double(data.count), unit: UnitInformationStorage.bytes)
                    print(size.converted(to: .kilobytes).formatted())
                }
            } catch {
                print(error)
            }
        }
        
    }
}

#Preview {
    PhotoFileSize()
}

///PhotosPhickerItem is a struct
extension PhotosPickerItem: @unchecked Sendable {}

or get the file size without loading the item into memory but it requires additional permissions.

import SwiftUI
import PhotosUI
struct PhotoFileSize: View {
    @State private var selectedItem: PhotosPickerItem?
    //Required or `itemIdentifier` will be nil
    let library: PHPhotoLibrary = .shared()
    var body: some View {
        PhotosPicker(selection: $selectedItem, photoLibrary: library) {
            Text("Selected Item")
        }
        
        .task(id: selectedItem) {
            //Only run this code if there is a selected item
            guard let selectedItem else {return}
            //Get the local identifier
            guard let id = selectedItem.itemIdentifier else {return}
            
            //Must have authorization to access the PhotoLibrary/PHAsset directly
            guard await PHPhotoLibrary.requestAuthorization(for: .readWrite) == .authorized else {return}

            let asset = PHAsset.fetchAssets(withLocalIdentifiers: [id], options: nil).firstObject!
            
            let resources = PHAssetResource.assetResources(for: asset)
            //Get the file sizw
            guard let fileSize = resources.first?.fileSize else  {
                return
            }
                print(fileSize.converted(to: .kilobytes).formatted())
 
        }
    }
}

#Preview {
    PhotoFileSize()
}

extension PHAssetResource {
    var fileSize: Measurement<UnitInformationStorage>? {
                
        guard let unsignedInt64 = self.value(forKey: "fileSize") as? CLong else {return nil}
        let sizeOnDisk = Int64(bitPattern: UInt64(unsignedInt64))
        return .init(value: Double(sizeOnDisk), unit: .bytes)
    }
}