1

I'm trying to learn how to use Core Data and I have a few sub-views that I want to pass the collection of items from Core Data through but I can't get it to work and the error messages make no sense to me.

This is what I have in my (main) ContentView:

@FetchRequest(sortDescriptors: [NSSortDescriptor(keyPath: \Item.firstName, ascending: true)]) var people: FetchedResults<Item>

I then have the following code in my call to the sub-view:

PeopleListView(people: people)

Inside the PeopleListView I have this to try and bind the variable.

@Binding var people: FetchedResults<Item>

The error I'm getting is the call to the sub view which is this:

Cannot convert value of type 'FetchedResults<Item>' to expected argument type 'Binding<FetchedResults<Item>>'

Can someone explain this in really simple terms on why this isn't working and how I can fix it? I'm really struggling with Core Data, I feel like there's so much going on behind the scenes that I just don't understand.

2

Replace people with $people. The latter resolves to the expected type Binding<FetchedResults<Item>>.

3

I'm having a similar problem when compiling a macOS app on Xcode 15.2, on macOS 14.2.1.

A view with a FetchedResults binding:

struct CountView: View {
    @Binding var items: FetchedResults<Item>
    var body: some View {
        Text("Number of items: \(items.count)")
    }
}

In the main ContentView:

    @FetchRequest(
        sortDescriptors: [NSSortDescriptor(keyPath: \Item.timestamp, ascending: true)],
        animation: .default)
    private var items: FetchedResults<Item>
// ...
        CountView(items: $items)

The compiler error:

Cannot convert value of type 'Binding<FetchRequest.Configuration>' to expected argument type 'Binding<FetchedResults>'

I don't understand why the type of $items is Binding<FetchRequest<Item>.Configuration>.

4

Exactly the same problem & error message, xcode Version 15.2 (15C500b). Can anyone explain how to pass @FetchRequest'ed fetchedresults to subviews? I need to pass fetched results to filter-like view, so that original list could be dynamically modified from child (Filter view).