One of the interesting things from WWDC this year in not just that Swift is adopting AsyncSequence but that Apple is fully behind it rather than further expanding support for Combine. This raises some interesting questions for the future of Combine, whether it is just destined to be a niche feature just supporting SwiftUI in particular ways, gets completely deprecated in future. This series (possibly just pair) of blog posts is going to compare the two by means of implementing mappers in both ways between them.

[Update: Marin Todorov has a nice post about the reverse if you want to get ahead on that.] 

if you want to have

While I haven't had the opportunity to use it in a real project yet I'm really liking the look of AsyncSequence and the whole of the structured concurrency approach.

These mappers will be implemented as raw conformances because the point is for me to learn and understand more. There may be better, more efficient or simpler approaches but I want to look into the details of how they work. I'll follow up if I find significantly better ways to do it.

Resuming continuations from actors doesn't work (Beta1-2)

One thing that has delayed this post is having hit some non-deterministic bugs I lost confident in my understanding of the Structured Concurrency and didn't want to share widely until I had established that the issues I was seeing were related to Swift/MacOS bugs rather a deadlock I was introducing by doing something substantially wrong.

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Update: This was all about Xcode 12 beta 1. There is probably nothing still relevant in beta 5 which includes better built in Core dat support including ways to directly bind on objects and even fetch requests so NSFetchedResultsControllers should become unnecessary. Will try to post again when I have explored further.

This might be a bit of a ramble, it certainly isn’t a carefully designed tutorial but will be a mixture of a few general early thoughts and a few minor gotchas I’ve already hit in my experimentation. I’m still in the stumbling and exploring phase and certainly haven’t mastered SwiftUI or Combine to any great degree yet. This may mean it will be helpful to few people, it is probably too heavy on the jargon if you haven’t already had a good look at SwiftUI and is too light on detail and probably inaccurate if you have gone deeply in. Certainly the shelf life of this post feels short. Feel free to let me know anywhere that I am wrong, or have missed the best documentation or give any feedback either by Twitter or in the comments.

I’m less comfortable with SwiftUI than I was with Swift itself at the similar stage 5 years ago. I believe this is going to be great but there is a mental shift required which I haven’t yet achieved.

I’m in the early stages of rewriting my first ever app (Fast Lists) to create a new version with all the toys from WWDC 2019. Including but not limited to Cloudkit Core Data syncing, SwiftUI interface, support for Mac and Watch (not just iOS as before). Multi window support. I’m also hoping to add some drag and drop support later but I haven’t even started looking at that yet. Because I’m trying everything at once my progress is a bit stop start and random at the moment but it does mean that there is normally another piece to work on if I get stuck.

This is all based on experience with Version 11.0 beta (11M336w) (the first beta) so many of these issues may be resolved very soon. In a few places I note the feedback numbers that I have raised around things that are either bugs or potential areas for improvement.

Core Data seems a conceptual match for SwiftUI

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