Give your simulator superpowers

RocketSim: An Essential Developer Tool
as recommended by Apple


Antoine van der Lee

Staff iOS Engineer at WeTransfer, founder of SwiftLee

Antoine van der Lee - About
Antoine van der Lee – About

Developing iOS apps since 2009. Currently at WeTransfer, Amsterdam


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Indie Watch Issue 9: RocketSim by Antoine van der Lee

Aryaman Sharda asked me questions about how I developed RocketSim, as well as how I started SwiftLee and grew it to the blog it is today.

Interview with highly sought-after blogger Antoine van der Lee

Shipbook interviewed me with questions about App Quality, blogging, debugging tools, and more. Check it out!

10 Years of iOS: Chatting With SwiftLee’s Antoine van der Lee

Interviewed by the iOS academy to share my story of 10 years of iOS development.

Indie Dev Monday

How and why did I develop RocketSim and how do I manage my time while working full-time at WeTransfer. It’s all covered in this Indie Dev Monday interview.

Interview: Antoine van der Lee

Get to know me a bit better! Why did I start SwiftLee, my advice on coaching, and my perspective on the future of Swift.

The Complete Guide to iOS and Swift Job Interviews

This is a fantastic guide full of tips for iOS and Swift Job Interviews. My perspective is shared among others like Sean Allen, Ash Furrow, and Kaya Thomas.


Swift for Good – A chapter on Operations in Swift

As part of a total of 20 authors, I’ve been writing a chapter for the Swift for Good book. All money earned has been donated to charity with a result of over $40,000 raised. You can read chapter 13 on Operations in Swift written by me!

Podcasts and YouTube interviews

Antoine van der Lee on Building and Leading Winning Teams

Discover practical strategies for optimizing workflows, overcoming knowledge silos, and adapting to the cutting-edge role of AI tools in software development.

You NEED this to Rank Better on the App Store #ASO

Ariel from the Appfigures team interviewed me in a live session on YouTube, asking me about our rating improvements in the WeTransfer app. Learn how you can increase your App Store ratings.

[S3E2] iOS-development bij WeTransfer met Antoine van der Lee

For my Dutch followers: CodeKlets interviewed me and asked questions about my career, what it’s like to be a developer at WeTransfer and how I manage my time for all my side projects.

103: “What’s new in Swift 5.5” with special guest Antoine van der Lee

Joining John Sundell to discuss latest Swift 5.5 features and the future of Swift, as well as a little background story of RocketSim.

Empower Apps – Maintaining & Migrating

Migrating projects to new languages like SwiftUI, maintaining a code mess and coding guidelines. It’s all covered in this two parts podcast episode.


Jeroen Leenarts interviews me about my day to day job at WeTransfer, RocketSim, and writing weekly at SwiftLee.

Ontwikkelaars over WWDC 2020: Bas Broek en Antoine van der Lee

Bas Broek and I discuss WWDC 2020 together with Gonny from iCulture in their Dutch podcast.

Inside WeTransfer’s App Testing Process with Antoine van der Lee

An interview with Darko Fabijan about our CI processes and automation, including a detailed explanation of how we do automated releases.

“It’s been a wild year” a Holiday Special with Donny Wals and Antoine van der Lee

Joining John Sundell‘s Swift by Sundell podcast together with Donny Wals talking about 2019 and looking ahead into 2020.

SwiftConf, NSSpain, Mobiconf, and FrenchKit – With Special Guest Antoine van der Lee

Joining Bas Broek and Benedikt Terhechte in their Contravariance podcast! We go over our experiences from a few conferences we’ve been visiting.

Developer Workflow Optimizations with Antoine van der Lee

Giving my best tips in the SwiftCraft episode hosted by Eman Harout covering a lot of content from my blog post Speeding up as a developer.

WWDC with John Sundell

Discussing my tips for WWDC together with John.

iCulture podcast #10: terugblik op WWDC 2019 voor ontwikkelaars

A Dutch podcast recording in which I tell everything about my experiences at WWDC 2019.

iCulture podcast #13: hoe word je appontwikkelaar?

A Dutch podcast recording in which me and Bas Broek tell you the best tips to become an app developer.


Upcoming and past speaking engagements of @twannl including video recordings and references to any online slides.

Video recordings

Harnessing the Potential: Swift Macros in Action
2023 BA: Swiftable, Buenos Aires, Argentina

Speeding up as an iOS Developer
2019 CocoaHeadsNL, Amsterdam

How to create a sustainable codebase
2018 AppDevCon, 2018

Building the new WeTransfer mobile app
2017 CocoaHeads, 2017

Using Functional Reactive Programming
2016 DOiOS, 2016


Speeding up as an iOS Developer

Using Functional Reactive Programming

Upcoming and past conferences


BA Swiftable – Harnessing the Potential: Swift Macros in Action
Buenos Aires, November 30th

NSSpain – Harnessing the Potential: Swift Macros in Action (Lightning)
NSSpain, September 14th & 15th

Students, Swift, Stars at WWDC – Panel
San Jose, June 6th

iOS Conf SG – Making the Most Out of Swift
Singapore – January 13th


Let it Swift – Any idea how to use some generics?
Poznań, Poland – November 9th

FrenchKit – Any idea how to use some generics?
Paris, France – September 29th

CHECK24 – Any idea how to use some generics?
Frankfurt, Germany – August 19th

SwiftConf – Any idea how to use some generics?
Cologne, Germany – August 18th

AppDevCon – Any idea how to use some generics?
Amsterdam, Netherlands – June 24th


SwiftLeeds – Data Races and Actors in Swift
Leeds, England – October 8


Let it Swift – Operations in Swift
Poznań, Poland – April 8

AppDevCon – Operations in Swift
Amsterdam, Netherlands – March 13

Swift Paris Meetup – Operations in Swift
Paris, France – January 30


CocoaHeadsNL at WeTransfer – Data races in Swift
Amsterdam, Netherlands – November 20

FrenchKit – Combine Workshop
Paris, Franch – October 7 & 8

Mobiconf – Combine Workshop
Krakow, Poland – October 3 & 4

Swift Island – Combine Workshop
Texel, Netherlands – July 3 & 4

CocoaHeadsNL at ABN Amro
Amsterdam, Netherlands – January 30


GDG Coimbra – Speeding up as an iOS developer
Coimbra, Portugal – Nov 24

Swift Heroes – Speeding up as an iOS developer
Turin, Italy – Nov 9

AppDevCon – How to create a sustainable codebase?
Amsterdam, Netherlands – Mar 16

MobOS – How to create a sustainable codebase?
Cluj-Napoca, Romania – Feb 16


CocoaHeads – Building the new WeTransfer mobile app
Amsterdam, Netherlands – Jul 19

Tweakers Dev Summit – Using Functional Reactive Programming
Utrecht, Netherlands – Feb 16


CocoaHeads – Using Functional Reactive Programming
Alkmaar, Netherlands – Nov 15

DO iOS – Using Functional Reactive Programming
Amsterdam, Netherlands – Nov 9


As a Lead iOS Engineer at WeTransfer, Antoine’s work is focused on code architecture and team processes. He’s passionate about contributing to the iOS community where you might know him from his weekly blog posts on his personal blog called SwiftLee. He particularly enjoys speaking on best practices for structuring code architecture in a way that creates sustainability, as well as open-sourcing frameworks and how iOS developers can be more successful in their work.