iOS 18 SwiftData ModelContext reset

Question

Created Jun ’24

Replies 16

Boosts 21

Views 6.8k

Participants 20

Since the iOS 18 and Xcode 16, I've been getting some really strange SwiftData errors when passing @Model classes around.

The error I'm seeing is the following:

 SwiftData/BackingData.swift:409: Fatal error: This model instance was destroyed by calling ModelContext.reset and is no longer usable. 
 
PersistentIdentifier(id: SwiftData.PersistentIdentifier.ID(url: x-coredata://34EE9059-A7B5-4484-96A0-D10786AC9FB0/TestApp/p2), implementation: SwiftData.PersistentIdentifierImplementation)

The same issue also happens when I try to retrieve a model from the ModelContext using its PersistentIdentifier and try to do anything with it. I have no idea what could be causing this.

I'm guessing this is just a bug in the iOS 18 Beta, since I couldn't find a single discussion about this on Google, I figured I'd mention it.

if someone has a workaround or something, that would be much appreciated.

Boost

Answer 1

danielbm OP

6d

@SplittyDev, your update was was very helpful, thank you!

I have two model containers: One for previews with in-memory storage only, and one for development with proper on-disk storage.

For that part, here's what I'm doing:

 extension ModelContainer {
 
    static var shared: ModelContainer = {
        if ProcessInfo.isPreview { return preview }
        // ...
    }()
 
    static var preview: ModelContainer = {
        // ...
    }()
}
 
public extension ProcessInfo {
    static var isPreview: Bool {
        return ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] == "1"
    }
}

With your answer and this, I managed to get it all working how I was hoping. :D

0

	SwiftData/BackingData.swift:409: Fatal error: This model instance was destroyed by calling ModelContext.reset and is no longer usable.

	PersistentIdentifier(id: SwiftData.PersistentIdentifier.ID(url: x-coredata://34EE9059-A7B5-4484-96A0-D10786AC9FB0/TestApp/p2), implementation: SwiftData.PersistentIdentifierImplementation)

	extension ModelContainer {

	static var shared: ModelContainer = {
	if ProcessInfo.isPreview { return preview }
	// ...
	}()

	static var preview: ModelContainer = {
	// ...
	}()
	}

	public extension ProcessInfo {
	static var isPreview: Bool {
	return ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] == "1"
	}
	}