Give your simulator superpowers

RocketSim: An Essential Developer Tool
as recommended by Apple

Issue 274
Jun 03, 2025

This week's SwiftLee Weekly covers:

  • Microapps architecture
  • Private APIs for hidden UIKit views
  • SwiftUI tracing using Macros

Enjoy this week's SwiftLee Weekly!

THIS WEEK'S BLOG POST

Unique values in Swift: Removing duplicates from an array

Removing duplicates from an array can quickly become a performance challenge when your array has thousands of items. In this week's article, we discuss performant options to efficiently get unique values, including an extension to filter by a specific property.

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 Codemagci to build and publish iOS and Android apps, also versioning and device provisioning. View on GitHub.

CURATED FROM THE COMMUNITY

Tips and tricks for when using SwiftUI’s ViewBuilder

I’m sure you’ve all used @ViewBuilder, but I don’t think you know all techniques described in this article!
swiftbysundell.com

Microapps architecture in Swift. Scaling.

I’m a fan of microapps architecture and use it a lot in RocketSim. Majid’s series can be a great way to get started.
swiftwithmajid.com

Automatic SwiftUI View Tracing with Swift Macros

I love the simplicity of using a Macro for all kinds of tracing solutions. This article suggests using a similar macro for things like analytics, error tracking, memory monitoring, and more.
medium.com

Accessorise Your Context Menu Interactions

Be warned: private APIs are in this article! Yet, they do open doors to UI that Apple uses, but we normally can’t.
sebvidal.com

Survey finds your mobile engineers lose 5 hours per release

Runway's 2025 survey of 300 mobile engineers reveals mobile teams lose 32.5% of their release time to hidden bottlenecks, manual coordination headaches, and the surprising inefficiencies automation hasn’t fixed. Find out how much your mobile releases are costing you and reclaim lost productivity by downloading the report.
runway.team

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.

No changes! It seems that they're keeping the changes for WWDC 😉

CODE SNIPPET OF THE WEEK

Fallthrough enums

You can find this post on Twitter/X, LinkedIn, or Bluesky.

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Antoine v.d. SwiftLee 
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@twannl
12:54 PM • Jun 2, 2025
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Retweets
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QUESTION OF THE WEEK

What is the best way to optimize my onboarding funnel?

You're promoting your app on socials, you've optimized your App Store landing page, and you've done everything to get that user to install your app. You've might even paid for advertising!

The user starts using your app, but where does the user end? Will they stick? Or do they stop using your app within a minute after using it?

The onboarding funnel of your app is just as important as all the steps before a user even installs. The higher the percentage of users ending up sticking to your app, the larger your revenue potentially becomes. You'll have more upsell opportunities for both your paywall as your app's added value.

I'm constantly revisiting RocketSim's onboarding as I'm learning from my Amplitude statistics. Even recently, I realized it might not be clear to users that you can use RocketSim for free as well. I decided to add an NSAlert which shows up when closing the paywall window. The hypotheses I've had is that users would quit the app completely after seeing the paywall, thinking it's a paid-only app.

The result looks as follows:

The initial three steps show similar results, but the drop-off after the paywall is much lower for my latest release. 66% instead of 54% of the users end up seeing RocketSim's Side Window, which is the key action for my app:

  • If users see the side window, they're most likely going to use and experience the app.
  • If they experience the app, they're most likely sticking
  • If they're sticking, they're more likely to eventually convert

In other words, I've probably increased my revenue in the long run! All by focusing on a single step of my onboarding funnel.

Want to have your question answered next week? Ask your question via this form (anonymously) or reply to this email with your question.

{% if subscriber.rh_reflink != blank %}EARN ROCKETSIM LIFETIME

Share and Earn RocketSim Lifetime & a 1-on-1 coaching session

Apple has recognized RocketSim as an Essential Developer Tool in the Mac App Store, and now you can get lifetime Pro access by sharing your unique referral link!

How to get started:

{{subscriber.rh_reflink}}

Rewards:

  • Earn your first reward after just 3 sign-ups!
  • Check your progress anytime using your referral dashboard.
  • The grand prize? A lifetime RocketSim license!

Several subscribers have already claimed their rewards—will you be next?{% endif %}

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

Antoine