load core data binary image data to UIIMage

Question

I have a CoreData Entity called Data that has an attribute called asset for image data:

extension Data {
    static func createImage(label: Label, image: UIImage, context: NSManagedObjectContext) {
        let newData = Data(context: context)
        newData.id = UUID()
        newData.type = "image"
        newData.label = label
        newData.setValue(image.pngData(), forKey:
                        "asset")
        newData.date = Date()
        context.saveContext()
    }

I can't seem to figure out how to load the binary image data into an UIImage.

var fetchRequest: FetchRequest<Data>
var data: FetchedResults<Data> {
        fetchRequest.wrappedValue
}

init(label: Label){
        let sortDescriptor = NSSortDescriptor(keyPath: \Data.date, ascending: false)
        let predicate = NSPredicate(format: "label == %@", label)
        self.label = label
        fetchRequest = FetchRequest<Data>(entity: Data.entity(), sortDescriptors: [sortDescriptor], predicate: predicate)
}

  var body: some View {
        LazyVGrid(columns: columns, alignment: .leading){
            ForEach(data, id: \.self) { dataItem in
                GeometryReader { gr in
                    Image(uiImage: UIImage(data: dataItem.asset ?? Data()) ?? UIImage())
}
}

And I get the error 'NSObject' is not convertible to 'Data'

I've also tried let uiImage: UIImage = UIImage(data: dataItem.asset)!

Which gives the error Cannot convert value of type 'Data?' to expected argument type 'Data'

This is how I set up the asset attribute:

could you try: if let imgData = dataItem.asset, let img = UIImage(data: imgData) { Image(uiImage: img) } else { Image(uiImage:UIImage()) } — workingdog support Ukraine
– workingdog support Ukraine, Commented Aug 20, 2021 at 2:56

Phil Dukhov · Accepted Answer · 2021-08-20 08:26:10Z

1

Your first error is because you've named your core data entity as Data, and were trying convert Foundation.Data to your own class

I suggest you rename your core data entity to prevent such mistakes in the future.

In case you can't do that for some reason(not this case, generally), and you have two classes with the same name from different modules, you can select the needed class with the specifying module before, like Foundation.Data

Second your error was because you were trying to unwrap the result of UIImage instead of your own data.

When you need to unwrap an item before passing it to a function. I suggest you to use one of the following methods:

Unwrap variable using .map and .flatMap:

dataItem.asset
    .flatMap { asset in
        UIImage(data: asset)
    }.map { uiImage in
        Image(uiImage: uiImage)
    }

Use .map and extend Data. I prefer this one for better readability. You could've extends UIImage in the same way to return Image, but for SwiftUI view it would look too strange and decrease readability to me:

dataItem.asset?
    .toUIImage()
    .map { uiImage in
        Image(uiImage: uiImage)
    }
---
extension Data {
    func toUIImage() -> UIImage? {
        UIImage(data: self)
    }
}

edited Aug 20, 2021 at 8:26

answered Aug 20, 2021 at 6:24

Phil Dukhov

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1 Comment

scientiffic Over a year ago

awesome, thanks so much! I renamed the entity and unwrapped the item using the flatMap you suggested and it worked.

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