SpamSieve 3.3.1 is an update of my Mac e-mail spam filter that improves the filtering accuracy and includes various optimizations, fixes, and updates for macOS 27. Some interesting engineering issues were:

• I’m still supporting macOS 10.13, but the app can now build with the macOS 12 deployment target in preparation for Xcode 27. The way Swift handles calling deprecated APIs remains annoying. You need workarounds like protocols to suppress a warning in a particular region of code. Often, I am updating to a newer API, but I want to continue using the old one on earlier versions of macOS. Right now I am heavily testing on macOS 26, so I would like to only deploy the new code there. Sometimes the initial versions of APIs are buggy, and I don’t want to have to retest every feature on every version. But Swift doesn’t like me to gate the calls to macOS 26 and later if the new API was actually introduced in, say, macOS 11.

• The most risky update was probably switching to the Swift API for Scanner. This is tricky because the current scan position changes from being based on UTF-16 indexes to String.Index. And in some cases my code was intentionally scanning into the middle of a combining character. I was really glad to have extensive tests here.

• Recent versions of Tahoe introduced a Core Data bug that broke save recovery (when invalid Unicode can’t be written to the database and we have to fix it up first). When the error comes in, SpamSieve looks under the NSDetailedErrorsKey key, but the value of this key is "NSDetailedErrorsKey" while the actual error info is under the key "NSDetailedErrors".

• Database corruption combined with a Core Data bug and two Swift behaviors were causing crashes. The root problem, I think, is that in this situation Core Data neglects to set the error pointer for -[NSManagedObjectContext countForFetchRequest:error:]. Normally, Swift would detect this and throw a generic nilError. However, this method signals errors by returning NSNotFound instead of nil. It’s annotated as swift_error(nonnull_error), which I think means that Swift doesn’t even look at the return value, only the (unset) error. So my code was receiving NSNotFound on the non-error path, treating it as a real count, and doing some math with it, which (by default in Swift) leads to a crash if there’s overflow. Now my code checks for NSNotFound and uses Int.addingReportingOverflow().

• I reimplemented Core Data batch fetching because of two problems with the fetchBatchSize option. First, it logs spurious errors when fetching from multiple stores at once. Second, it leads to high memory use. It will load objects in batches, but it never releases the earlier batches. You can manually refault objects that you no longer need, but it will still hold onto the full object shells, which can add up. My implementation only holds onto IDs, and it can fetch the IDs using a different context than the objects to push more work to background threads.

• I’m now using String.makeContiguousUTF8() in various places to avoid slow iteration of bridged strings.

• There was a regression where some menu code could crash on macOS 10.13. -[NSMenu setItemArray:] is only available on macOS 10.14 and later, whereas the getter is always available. With old Objective-C, the two methods could be annotated with separate availabilities. The Objective-C property syntax doesn’t allow this, so there’s no way for the compiler to flag calls where the setter is missing.

• The AppleScript support works much better with large data sets. The key, I think, is to never return an array to Cocoa for a scripting property/element. First, if you give it a lazy array it will sometimes try to access all the elements even if it only needs a few. And, second, AppleScript will run out of memory if the array is too large. By using indexed accessors, you can maintain laziness and only convert one object to a descriptor at a time. By caching a batch-fetching collection, you can limit the number of fetches and respond quickly when AppleScript requests individual objects.

Previously:

• Xcode 27 Announced
• SpamSieve 3.3
• Swift Proposal: Precise Control Flags Over Compiler Warnings
• Swift at 10

SwiftData updates:

Section your query results by creating your query with a macro that takes a sectionBy parameter, as listed on the Additional query macros page.

Use types that conform to Codable in a model, including types you don’t control directly, by using the codable option for Schema.Attribute.

Receive real-time updates to models that match specified fetch criteria by using the ResultsObserver type.

Observe remote model changes with the HistoryObserver type.

What’s new in SwiftData:

Discover the latest enhancements to SwiftData. We’ll show you how to persist custom and third-party types using Codable, and group fetched data into sections in your SwiftUI app. We’ll also explore how to observe data store changes anywhere else using ResultsObserver and HistoryObserver, giving you the flexibility to drive powerful state objects and react precisely to model updates.

Again, there seems to be nothing new in Core Data this year, nor any communication about it. There’s still no interoperability for object IDs. The SwiftData changes seem fine but don’t really address the new framework’s deficiencies relative to Core Data. It seems like there are still basic problems with threading. I just don’t understand how Apple is deciding what to prioritize with this framework.

With SwiftUI, the bones seem questionable, but at least we can see that Apple is full steam ahead, with substantial progress to address limitations and pain points. SwiftData seemed to have better bones and is much less ambitious. Getting it right seemed like just a matter of follow through. But, for some inexplicable reason, it seems to lack the resources and/or urgency to reach its potential. And even though SwiftUI is clearly the chosen one, AppKit remains in development. Meanwhile, Core Data seems to be abandoned, even though SwiftData feels more like a side quest than a genuine attempt to supplant it.

The implicit message, for those who have build the core of their app on top of Apple’s old persistence framework, seems to be that Apple is not looking out for their needs. Core Data will surely get maintenance to the extent that Apple’s own apps need it, but there’s no evidence of a future or even a migration plan. The answer, I guess, is third-party frameworks, but that’s not an easy migration, either, since none is even as close a match as SwiftData.

Add persistence with SwiftData:

Experience SwiftData in action as we add persistence to an existing app. We’ll show you how to define your data models and seamlessly integrate persistent data with SwiftUI. You’ll also learn foundational skills for managing your app’s state using this expressive, declarative API.

SwiftData Group Lab:

Join us online for a deep dive into WWDC26 with Apple engineers and designers to ask questions, get advice, and follow the discussion about the week’s biggest SwiftData announcements.

macOS Golden Gate 27 Beta Release Notes:

Fixed: You might experience a deadlock for @Query when saving a ModelContext on a background actor while scheduling new async tasks for a ModelActor.

Paul Hudson:

I am so pleased to say these words: IT IS A BIG YEAR FOR SWIFTDATA! 🎉

Mohammad Azam:

SwiftData predicates can now work directly with enum values, resulting in cleaner models and simpler query code.

[…]

In iOS 27, Apple introduced support for compound predicates through the Predicate(all:) and Predicate(any:) initializers, making it easier to build queries dynamically based on user input.

I’m not sure why that took so long.

The framework is gradually moving beyond simple demos and becoming easier to use in larger, more sophisticated projects.

[…]

iOS 27 is the first release where many of the framework’s early rough edges have started to disappear.

Matt Massicotte:

Results of my now-yearly check to see if SwiftData’s ModelActor continues to sometimes run code on the main thread: yes it does

Fatbobman:

Compared with @Query gaining support for section fetches, and ResultsObserver enabling observation of query result changes outside views, I am more interested in @Attribute(.codable). It provides a clearer storage intent and gives developers a way to avoid falling into the black box of composition.

Of course, @Attribute(.codable) is not a silver bullet. It is more like a clearly defined escape hatch SwiftData provides for opaque Codable types: suitable for storing external types that you cannot model yourself, but still genuinely need to persist. The cost is that this content cannot participate in SwiftData’s predicate, sort, or migration awareness. Precisely for this reason, its value lies not in being “more powerful,” but in being “more explicit.”

However, SwiftData still does not provide cloud syncing for public / shared data, nor have I seen a clearer signal of performance improvements. These issues will continue to limit its adoption. For many developers, SwiftData this year feels more like it is filling key gaps rather than making a leap significant enough to fundamentally change confidence in it.

Helge Heß:

Codable types in SwiftData seem pretty lame given that SQLite absolutely does have JSON support and does support queries on it?

But the funnier thing in the MKMapItem.Identifier example is that MKMapItem.Identifier is a RawRepresentable==String, so it could actually be stored as a String in the store.

Previously:

• WWDC 2026 Links
• Batch Delete in SwiftData
• SwiftData’s ModelActor Is Just Weird
• SwiftData Runtime
• Ways SwiftData’s ModelContainer Can Error on Creation
• SwiftData and Core Data at WWDC25
• Returning to Core Data
• Dynamic Swift Predicates in macOS 14 and iOS 17