Give your simulator superpowers

RocketSim: An Essential Developer Tool
as recommended by Apple

Issue 282
Jul 29, 2025

This week's SwiftLee Weekly covers:

  • A threading risk for Combine & Swift Concurrency
  • Flux pattern in Swift
  • A crash debugging experience

Enjoy this week's SwiftLee Weekly!

THIS WEEK'S BLOG POST

​Combine and Swift Concurrency: A threading risk​

Migrating to Swift Concurrency brings all kinds of insights. Last week, I found an unexpected crash in RocketSim, caused by a Combine pipeline. It resulted in some crucial insights for those using Combine with Swift Concurrency.

SPONSORED

​Fastlane alternative - Codemagic CLI tools​

Are you tired of Ruby and Fastlane installation issues? There's got to be a better way! Discover Codemagic open source CLI tools. It is not a drop-in replacement for all of what Fastlane does (screenshots for example), but we use it at Codemagic to build and publish iOS and Android apps, also versioning and device provisioning. View on GitHub.

CURATED FROM THE COMMUNITY

​A Peek into My Debugging Process (With Real Examples)​

You find a crash—how do you solve it? Pol Piella shares its journey, and it’s very close to how I would tackle issues in my apps.
​polpiella.dev​

​Flux pattern in Swift​

For those looking to get inspired by architectural patterns: meet Flux—an approach to a unidirectional data flow.
​swiftandpizza.wpcomstaging.com​

​Uncertain⟨T⟩​

What if uncertainty were encoded directly into the type system?
​nshipster.com​

​Creating amazing loading animations with SF Symbols.​

Before you start writing custom animations—consider SF Symbols. Especially if you’re able to target iOS 17+.
​danielsaidi.com​

​Deciding between ‘let’ and ‘var’ for Swift struct properties​

You’d say it’s hard to write an article just on ‘let’ and ‘var’. It’s something we use so often, you would say there’s nothing new to learn. I loved the creativity behind the @Readonly property wrapper!
​swiftbysundell.com​

SWIFT EVOLUTION

An overview of last week's Swift Proposal state changes. Check them out when they're in review, as it's your opportunity to influence the direction of Swift's future.

It's holiday season, no updates this week!

WHAT I'M WORKING ON

Core Data and Swift Concurrency

I've been giving conference talks for many years now and during COVID times I had one special talk given at NSSpain: Best Practices in Core Data. It was a pre-recorded video, since in-person conferences were not allowed.

This week, I've had a flashback. Since I'm diving into Core Data & Swift Concurrency, I had to go back to my Core Data Best Practices GitHub repository. So many learnings from the past that resurfaced!

I always have been enjoying Core Data (Yes, I'm probably an odd one out here). While working on the Core Data module for my Swift Concurrency Course, I went on a classic journey of writing complex solutions.

Why classic?

Well, I found out after two hours of writing custom actor executors using a managed object context that it's actually not really needed to make Core Data work with Swift Concurrency. I believe it's a true skill to realize and accept that the code you wrote can basically be thrown away.

I did not, I wrote down all my learnings and shared all the code in the lesson since I believe it's actually a useful insight for my students. The actor executor works great, I just think it overcomplicates things. Keeping code readable without hidden implementation details (like a custom executor) would always be my preference.

FYI: The Core Data course module will be released this Thursday, together with several Swift 6.2-related concurrency lessons. You can get the course here.

​

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Thank you so much for your support, and until next Tuesday,

Antoine

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