Give your simulator superpowers

RocketSim: An Essential Developer Tool
as recommended by Apple

Issue 209
Sep 18, 2025

This week's SwiftLee Weekly brings you optionals, whether Xcode Cloud is ready for adoption, and some exciting Swift concurrency-related articles.

Enjoy this week's SwiftLee Weekly!

THIS WEEK'S BLOG POST
Did you know optionals have existed since the very beginning of Swift? They weren't always as great as today, but I can't imagine a world without those question marks everywhere throughout the codebase. Let me share five things you should know to make the most of optionals.

SPONSORED
Is Xcode Cloud ready for adoption? How do I solve flaky tests? I’ve shared this all in this podcast by Bitrise. Listen here.

MONTHLY GIVEAWAY
This month’s SwiftLee Giveaway allowed you to win one of the five copies of The Mobile System Design book, authored by Tjeerd in ’t Veen.

I’m excited to announce the following winners:
  • S. Maitri
  • M. Shenoy
  • Vince
  • T. Hilker
  • Filippos
We’ll get in touch with you shortly.

CURATED FROM THE COMMUNITY
The fact that DispatchQueue.main works together with @MainActor sparked the interest of Ole Begemann, who decided to dive deeper into how this behavior works.
NSPredicate’s replacement comes with pure Swift solutions for data processing and evaluation. Fatbobman explains how they work in this in-depth article.
You probably do understand a lot about how isolation works, you just don’t realize it yet.Matt does a great job explaining what isolation means in Swift.
Defining custom errors is one thing, but ensuring clear descriptions can make a difference for your future self. Gabriel shows how you can improve your debugging experience.
When I started developing apps for iOS 4, it was much more common to use Xcode’s instruments to improve the performance of my apps. I was glad to see this article by Jacob Bartlett as it shows the power instruments still have today.

SWIFT EVOLUTION
An overview of last week's Swift Proposal state changes. Make sure to check them out when they're in review, as it's your opportunity to influence the direction of Swift's future.
ImplementedSE-0416 Subtyping for keypath literals as functions
AcceptedSE-0419 Swift Backtrace API

QUESTION OF THE WEEK
This week’s question comes from Lucas:

How to become a speaker at conferences?

When I started writing weekly articles 5 years ago, I actually did this to increase my chances of getting invited to conferences. I figured it was hard for me as an ‘unknown’ developer to get myself a spot at one of the many conferences.

While writing weekly did definitely help me to get invited more easily, my original view changed. Since many talk proposals are anonymous, it was not my ‘popularity’ that would influence getting picked.

Altogether, I think it’s important to realize you’ll always be rejected for conferences. Even the most experienced speakers don’t always get accepted since it’s your talk topic that needs to fit the conference’s overall timeline.

Once you do get accepted, make sure to read my article Presentation tips for performing professional Swift talks, which I’m updating with new learnings after each given talk.

Want to have your question answered next week? Ask your question on LinkedIn or Twitter.

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