CoreData + Picker: confusion

Question

Created Apr ’21

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Hi,

I have two CoreData entities, "Product" and "StorageLocation"; there is a one-to-many relationship between them; "Location" can have multiple product, and product just one location.
Idea behind is:

User create a product a choose from a picker the location, then the product is saved and shall be saved the relationship too (location); but the picker gives me back a string, not a "Location" entity which is expected when saving a new product.

Here my code:

Code Block language
@State private var storageLocation = "AAAA"
@FetchRequest(
        sortDescriptors: [NSSortDescriptor(keyPath: \StorageLocation.name, ascending: true)],
        animation: .default)
    private var storageLocations: FetchedResults<StorageLocation>
Form {
                Picker(NSLocalizedString("storage", comment: "storage"), selection: $storageLocation) {
                    ForEach(storageLocations, id: \.self) { (storageLocation: StorageLocation) in
Text(storageLocation.name!).tag(storageLocation.id)
            }

How can I get back from the picker a Location object?

Thanks
Marco

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Answer 1

marcocan OP

Apr ’21

I digged more into the topic and the problem is not in the picker actually, but in CoreData.
What I have is an ActionSheet where I can create a new "Product" entity; in this sheet there is a picker to pick a storage location which is basically another entity.
The function addProduct will save then to CoreData

Code Block private func addProduct(id: UUID, name: String, actualQty: Int, expDate: Date, location: StorageLocation) {
        withAnimation {
            let newItem = Product(context: viewContext)
            newItem.id = id
            newItem.name = name
            newItem.qty = Int32(actualQty)
            newItem.expDate = expDate
            location.addToProducts(newItem)

After having watched few CoreData videos/tutorials, I understood I have to use the function "addToProducts" provided by the CoreData classes.
But when I do this, I get the following error:

Code Block Thread 1: "-[StorageLocation addProductsObject:]: unrecognized selector sent to instance 0x600000abcf40"

and the app crashes;

I looked for the error, but everything I found was an incosistency between model and classes, but this is not my case.

Any idea/hints?

Thanks
Marco

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