[WIP] Attempt at porting to Swift using Claude Code

[lawrence-forooghian]

Based on top of #2105.

Summary

This was an experiment at getting Claude Code to port this repo to Swift. I had thought that this might be a simple, low-risk way of starting to modernise this SDK. But it turned out not to be as simple as I had hoped. A lot of the issues come from Swift being a lot stricter about nullability than Objective-C. And then Claude sometimes tries to fix this itself but without enough context to really be able to reason about what may or may not be nullable.

Current state:

• there are Markdown documents at the root of the repository describing the task that Claude undertook as well as its progress (I think that it may have missed updating the progress document at a few moments so it might not be fully up to date)
• the SDK itself is compiling on macOS (not iOS because Claude wasn't trying to get that to pass — so the push notification code probably has further issues)
• there is a mishmash of various ways in which we've tried to fix nullability mismatches:
  • sometimes Claude just inserted its own default values e.g. ?? ""
  • sometimes we're using the unwrapValueWithAmbiguousObjectiveCNullability function that I told it to use
  • sometimes it's just doing force unwraps
• the test suite is compiling but after commenting out a bunch of tests, in some cases entire test files
  • and of the tests that are compiling, lots are failing

I have a bunch of further notes about this that I wrote along the way, but which I don't think worth writing up right now:
ably-cocoa Swift migration, Sep 2025.md

Conclusion

I don't think that this approach has yet proven itself to be viable. I originally proposed it because I thought it would be quick and low-risk compared to trying a rewrite in Swift from scratch. I am not as convinced now. I think that if we were to try and get this migration approach to work we might end up sinking a load of time into it and ending up with something that we have little confidence that it works, which means it's no longer low-risk.

This was 4 days of work and I think we should probably cut our losses on this approach for now and investigate alternatives.

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✨ Finishing touches

🧪 Generate unit tests

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch 2025-09-08-third-claude-code-attempt-at-porting-to-swift

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