If I use a Codable enum as the type in an array property on a Model, I get a crash. The message is something like: Illegal attempt to use a Optional(Swift.Mirror.DisplayStyle.enum) as a Property Minor change code example from a fresh project using SwiftData: @Model final class Item { var timestamp: Date var choices: [Choice] init(timestamp: Date, choices: [Choice]) { self.timestamp = timestamp self.choices = choices } } enum Choice: String, Codable { case beep, bloop } ContentView (largely unchanged): import SwiftUI import SwiftData struct ContentView: View { @Environment(\.modelContext) private var modelContext @Query private var items: [Item] var body: some View { NavigationView { List { ForEach(items) { item in NavigationLink { VStack { Text("Item at \(item.timestamp, format: Date.FormatStyle(date: .numeric, time: .standard))") Text("\(item.choices.map({"\($0.rawValue)"}).joined())") } } label: { Text(item.timestamp, format: Date.FormatStyle(date: .numeric, time: .standard)) } } .onDelete(perform: deleteItems) } .toolbar { #if os(iOS) ToolbarItem(placement: .navigationBarTrailing) { EditButton() } #endif ToolbarItem { Button(action: addItem) { Label("Add Item", systemImage: "plus") } } } Text("Select an item") } } private func addItem() { withAnimation { let newItem = Item(timestamp: Date(), choices: [.bloop, .beep]) modelContext.insert(newItem) } } private func deleteItems(offsets: IndexSet) { withAnimation { for index in offsets { modelContext.delete(items[index]) } } } } #Preview { ContentView() .modelContainer(for: Item.self, inMemory: true) } This is strange and seems like a bug as if I use Codable structs in this instance it is fine. Yet, if that Codable struct has an enum as a property, it also crashes with a different error. Working: import Foundation import SwiftData @Model final class Item { var timestamp: Date var choices: [Choice] init(timestamp: Date, choices: [Choice]) { self.timestamp = timestamp self.choices = choices } } struct Choice: Codable { let foo: String } Also doesn't work: import Foundation import SwiftData @Model final class Item { var timestamp: Date var choices: [Choice] init(timestamp: Date, choices: [Choice]) { self.timestamp = timestamp self.choices = choices } } struct Choice: Codable { enum SpecificChoice: String, Codable { case beep, bloop } let foo: SpecificChoice } It seems really odd and arbitrary that an enum would cause these issues. There may be other cases involving enums, but to wrap up it seems enums as properties of Codables that live within an array on a SwiftData model, or an array of enums on a SwiftData model cause crashes.