profile

SwiftLee Weekly by Antoine van der Lee

SwiftLee Weekly - Issue 321

Published about 2 months ago • 4 min read

This week's SwiftLee Weekly covers:

  • SwiftUI Animations
  • SwiftUI Performance Tuning
  • Column breakpoints in Xcode

Enjoy this week's SwiftLee Weekly!

THIS WEEK'S BLOG POST

​Immediate tasks in Swift Concurrency explained​

Immediate tasks are new in Swift 6.2 and a useful tool when working with Swift Concurrency. You really only should use it when you truly know what it's doing, which is why I wrote this week's article in detail.

SPONSORED

​Stop waiting. Start shipping.​

Shared runners, queued jobs, throttled Xcode builds — CI shouldn’t slow you down. Flow Swiss gives you dedicated Apple Silicon machines, yours alone. No noisy neighbors, no limits — just raw Mac mini and Mac Studio performance in the cloud, ready in seconds. New Xcode dropped? You’re ready day one. Learn more.

CURATED FROM THE COMMUNITY

​An Odometer-Style Number Animation in SwiftUI​

If you love animations and you’re using SwiftUI, you’ll definitely enjoy this animation example by Artem Mirzabekian.
​livsycode.com​

​Optional has a take() function​

Some Swift features take you years to discover, like this take method on optionals explained by Scott Berrevoets.
​scottberrevoets.com​

​Recording & Analyzing SwiftUI Instruments Traces​

SwiftUI Performance Tuning just got easier: let your agents do it using this Agent Skill update by Pol Piella.
​github.com​

​Making breakpoints work with single-line code blocks​

Ever heard about Column Breakpoints in Xcode? If not, this article by Peter Ringset is a must-read.
​peterringset.dev​

​SwiftUI: Refreshable Task Cancellation​

I’ve used the refreshable modifier in SwiftUI plenty of times, but I wasn’t aware of the risk Anton Gubarenko explained.
​antongubarenko.substack.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.

WHAT I'M WORKING ON

An agent-first protocol (rs/1) for Simulator Navigation

As you might know from previous newsletter issues: I'm working on a bundled RocketSim CLI. I want to reinvent how agents navigate through Simulators, and reduce token costs & time spent. RocketSim has the unique advantage of running in the background, allowing for optimizations other popular tools can't do.

I created 5 testing scenarios using the system settings app installed on every Simulator. Comparing the latest RocketSim CLI version to popular open-source alternatives, the results are quite impressive:

  • ~12x fewer tokens
  • 1.6x faster execution
  • 4x fewer wrong taps

RocketSim is able to do this due to its unique agent-first protocol (called rs/1) instead of relying on raw AX dumps. It also has a live snapshot store which allows the agent to reuse state instead of paying to rediscover the UI on every turn. Combined with semantic actions, waits, and typed errors, the agent models have to guess less and get faster to their end destination.

I've also spent a lot of time improving the discoverability of elements on screen. In my experience, elements like tab bars and navigation bars weren't always discovered by other tools.

Finally, installation will be easy due to a bundled CLI & Agent Skill, that will be symlinked from the settings screen commands:

I'm working hard this week and I hope to get it out of the door before next week, so stay tuned!

UNTIL NEXT TIME

Continue your Swift development journey

I hope you've enjoyed this week's content. You don't have to wait till next Tuesday for more insights, I share every day on these channels:

Or earn lifetime access to RocketSim & my Swift Concurrency Course by becoming an affiliate of my newsletter.

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

Antoine

Thanks for being a SwiftLee subscriber!
​
All my content is available to you for free. Like what I do and want to support me?
​Buy me a coffee or try RocketSim, an Essential Developer Tool as recommended by Apple.

This newsletter is built with Kit.
Need my experience? Book a 1:1 with me.

You're receiving this because you signed up for SwiftLee Weekly. If you'd prefer not to hear from me, you can manage your preferences here.

SwiftLee Weekly by Antoine van der Lee

Join 27K+ iOS Developers who get weekly updates on Swift & SwiftUI.

Swift Evolution updates, 5 top community articles covering Swift development topics.

Read more from SwiftLee Weekly by Antoine van der Lee

This week's SwiftLee Weekly covers: What's new in SwiftData? A peek into Xcode 27' SwiftUI Agent Skill Using Claude with Foundation Models Enjoy this week's SwiftLee Weekly! THIS WEEK'S BLOG POST SwiftUI Best Practices, straight from Apple's Xcode 27 Agent Skill If you’re following me for a while, you know I love building Agent Skills. That’s why I couldn’t resist peeking deeper into Apple’s Agent Skills and I found a lot of great learnings regarding SwiftUI Best Practices.avanderlee.com...

about 4 hours ago • 5 min read

This week's SwiftLee Weekly covers: Xcode 27's Agent' Skills Is RocketSim sherlocked? An often used Property Wrapper that changed into a macro in SwiftUI Enjoy this week's SwiftLee Weekly! THIS WEEK'S BLOG POST Using Xcode 27's Agent Skills in Claude, Codex, and Cursor It’s WWDC week and we had a lot of announcements. It was hard to pick a topic to write on, since there’s so many good things! I decided to tell you all about the Agent Skills that ship with Xcode 27 and how you can use them in...

7 days ago • 4 min read

This week's SwiftLee Weekly covers: I built a new app: Introducing MCP Beast Stateless actors? WWDC Quiz to warm you up Enjoy this week's SwiftLee Weekly! THIS WEEK'S BLOG POST WWDC 2026: My predictions and wishes In a week, we will know what Apple has been working on for months. It’s like Christmas for us Apple developers, and in this week’s article, I want to take you through my wishes and predictions.avanderlee.com SPONSORED Is Your iOS App Secure? Defend against static analysis and...

14 days ago • 4 min read