After the significant issues with the ModelActor in iOS 18, it seemed like the ModelActor became more stable with iOS 18.1 and macOS 15.1.
However, I’m still encountering problems and crashes. I wanted to ask if these issues are related to my persistence layer architecture or if they’re still inherent to the ModelActor itself.
I’ve generally followed the blog posts:
https://fatbobman.com/en/posts/practical-swiftdata-building-swiftui-applications-with-modern-approaches/
and
https://brightdigit.com/tutorials/swiftdata-modelactor/
and aim to achieve the following:
I have a single DataProvider that holds the ModelContainer and uses it to configure and initialize a single DataHandler. These are created once at app launch and injected into the SwiftUI view hierarchy as EnvironmentObjects. Since I need to access the SwiftData models not only in SwiftUI but also indirectly in ViewModels or UIKit views, all read operations on the models should go through the DataProvider (and its MainContext), while all other CRUD operations are handled centrally via the single DataHandler (executed within a single ModelActor).
Additionally, I want to monitor the entire container using another ModelActor, initialized in the DataProvider, which tracks changes to objects using TransactionHistory.
I’ve managed to implement this to some extent, but I’m facing two main issues:
1. ModelActor and Main Actor Requirement
The ModelActor only updates SwiftUI views when initialized via the maincontext of the ModelContainer and therefore runs on the Main Actor. It would be ideal for this to work in the background, but the issue with the ModelActor that existed previously doesn’t seem to have been resolved in iOS 18.1/macOS 15.1—am I wrong about this?
2. Frequent Crashes (more severe) Crashes occur, especially when multiple windows on macOS or on iPad access the same DataHandler to update models. This often leads to crashes during read operations on models by a SwiftUI view (but not only), with logs like:
error: the replacement path doesn't exist: "/var/folders/gs/8rwdjczj225d1pj046w3d97c0000gn/T/swift-generated-sources/@__swiftmacro_12SwiftDataTSI3TagC4uuID18_PersistedPropertyfMa_.swift"
Can't show file for stack frame : <DBGLLDBStackFrame: 0x34d28e170> - stackNumber:1 - name:Tag.uuID.getter. The file path does not exist on the file system: /var/folders/gs/8rwdjczj225d1pj046w3d97c0000gn/T/swift-generated-sources/@__swiftmacro_12SwiftDataTSI3TagC4uuID18_PersistedPropertyfMa_.swift
This error usually happens when there are multiple concurrent accesses to the DataHandler/ModelActor. However, crashes also occur sporadically during frequent accesses from a single view with an error like "the replacement path doesn't exist."
It also seems like having multiple ModelActors, as in this case (one for observation and one for data changes), causes interference and instability. The app appears to crash less frequently when the observer is not initialized, but I can’t verify this—it might just be a coincidence.
My Question: Am I fundamentally doing something wrong with the ModelActors or the architecture of my persistence layer?