Module verification must be enabled in order for Swift to use the module

Ugh. This was annoying to figure out. If you have a framework target in Xcode with a modulemap – e.g. because you’re wrapping a C or C++ library for use in Swift – you must keep the module verifier enabled (the ENABLE_MODULE_VERIFIER build setting) for that framework, otherwise any Swift targets using that framework won’t… Read more

SwiftUI drag & drop does not support file promises

SwiftUI doesn’t offer anything equivalent to NSFilePromiseProvider, i.e. to write data to the drop destination. You have to ditch SwiftUI and use AppKit’s drag & drop APIs instead. FB13583826. Is that it? I know that’s not a very helpful in some sense, but I wasted days trying to figure out how to implement this very… Read more

Bad API example: FileManager’s url(for:in:appropriateFor:create:)

I find FileManager‘s url(for:in:appropriateFor:create:) to be very unintuitive. It seems to have multiple, largely-orthogonal functions. It can provide paths to common folders (albeit badly). It can create temporary folders. It can locate volume-specific bins (Trash folders). It is an example of bad API design. Specifically, regarding cohesion: the principle that an API should have one… Read more

Creating files safely in Mac apps

Creating a file is a pretty basic and conceptually simple task, that many applications do (whether they realise it or not – library code often does this too, at least for temporary files such as caches or for communicating between programs). So you’d think it’d be trivial to do correctly. Alas, it is not. ☝️… Read more

NSImage is dangerous

Screenshot of an excerpt from Xcode's debug console showing the output of AddressSanitizer, having detected data race involving NSImage.

NSImage is formally documented as largely not thread-safe: The following classes and functions are generally not thread-safe. In most cases, you can use these classes from any thread as long as you use them from only one thread at a time. Check the class documentation for additional details. Apple’s Threading Programming Guide > Appendix A:… Read more

Reminder: macOS system frameworks binaries are hidden (since Big Sur)

Every now and again I’ll go to do something really innocuous with an Apple framework, like disassemble it in Hopper or check the link headers. And every. single. time. I forget that Apple did some really weird shit in Big Sur, and removed the binaries. $ ls -lh /System/Library/Frameworks/AppKit.framework/Versions/Current/AppKit ls: /System/Library/Frameworks/AppKit.framework/Versions/Current/AppKit: No such file or… Read more