I started iOS development in 2009. Since then I have worked in several companies in Germany. In my spare time I write books about Test-Driven iOS development and having fun with iOS development. Even though I mostly worked in agencies, I enjoy most working on a product over a long time.

Skills

iOS development

Master
  • swift
  • objc
  • tdd
  • xcode
  • coordinator-pattern
  • json
  • swift-package-manager

Objective-C

Master
  • objc
  • objective-c
  • categories
  • protocols
  • Model View Controller

Swift

Advanced
  • swift
  • async-await
  • generics
  • protocol-oriented-development
  • swift-package-manager

SwiftUI

Intermediate
  • swiftui
  • user-interface
  • declarative

Unit Testing in iOS

Master
  • unit-tests
  • testing
  • XCTest
  • snapshot-tests

Test-Driven Development

Master
  • TDD
  • Xcode
  • unit-tests

Python

Beginner
  • python
  • script

Kotlin Multiplatform

Beginner
  • kmm
  • kmp
  • multiplatform
  • kotlin

Work Experience (5)

Dec 2024 - Current
iOS/macOS developer
zollsoft GmbH
 Remote
The main product of zollsoft is tomedo, a practice management system for macOS and iOS. Most of the emploees of zollsoft work remote. We are currently about 160 macOS and iOS developers organized in teams of about 2-9 people.
  • I worked on (new and old) Objective-C and Swift code.
  • I added UI- and Unit-Tests to the iOS code base.
Aug 2019 - Nov 2024
iOS developer
Rocket Apes GmbH
 Remote
Rocket Apes is a small agency in Solingen Germany. We work 100% remote, and even did before COVID. All developers are highly self-driven but still know when to ask their colleagues for help.
  • As a very small team we managed to build the Danakil Wünschelrute. It's an app for a large exhibition in Erfurt Germany for the Federal Garden Show. https://apps.apple.com/de/app/danakil-wünschelrute/id1572995684
  • Maintain and support for very old apps written in Objective-C.
Oct 2014 - Jul 2019
iOS developer
energy app provider GmbH
 Remote and Essen
At every app provider we build about 30+ apps using a self created white label framework. All code was written in Objective-C as Swift and its support in Xcode was considered to be not mature enough. This turned out to be a good decision.
  • 2,5 iOS developers maintaining a large code base
  • Reducing the number Storyboard files in the project from 280 to 80 to reduce maintenance issues
Aug 2012 - Sep 2014
iOS developer
Appseleration GmbH
 Düsseldorf
At Appseleration I build apps for customers. I worked in a team of 3 to 4 iOS developers.
  • We build the iOS and Android app of the music streaming service Ampya
  • We build all Vodafone apps for the German market
May 2011 - Jul 2012
iOS developer
Vela Entertainment Studios GmbH
 Düsseldorf
This was my first job as an iOS developer. I was the only iOS developer and soon realized that I need other iOS developers to learn from them.
  • I build a comic reading app that automatically switched to the different panels on the comic page
  • I build a language learning app. Quite basic but I was in my early carreer

Projects (3)

Xcode.tips
Feb 2022 - Current
  • xcode
  • tips
Drawn Xcode tips
  • Mentioned often in several iOS dev newsletters
Astrodon
Nov 2022 - Current
  • xcode
  • macOS
  • Objective-C
macOS client for Mastodon
  • 100% Objective-C and AppKit
  • No AI used
Coordinates Watchface
Apr 2026 - Current
  • C
  • Watchface
Watchface for the Pebble watch
  • Pure C code
  • No AI used

Education (2)

2004 - 2007
PhD
 Physics
University Heidelberg, Germany
2001 - 2004
Diplom
 Physics
University Heidelberg, Germany

Publications

1 Apr 2022
Test-Driven iOS Development with Swift, Fourth Edition in Packt
Test-driven development (TDD) is a proven way to find software bugs earlier on in software development. Writing tests before you code improves the structure and maintainability of your apps, and so using TDD in combination with Swift 5.5's improved syntax leaves you with no excuse for writing bad code. Developers working with iOS will be able to put their knowledge to work with this practical guide to TDD in iOS. This book will help you grasp the fundamentals and show you how to run TDD with Xcode.
1 Aug 2020
Build Location-Based Projects for iOS in Pragmatic Bookshelf
Coding is awesome. So is being outside. With location-based iOS apps, you can combine the two for an enhanced outdoor experience. Use Swift to create your own apps that use GPS data, read sensor data from your iPhone, draw on maps, automate with geofences, and store augmented reality world maps. You’ll have a great time without even noticing that you’re learning. And even better, each of the projects is designed to be extended and eventually submitted to the App Store. Explore, share, and have fun.
30 Oct 2017
Test-Driven iOS Development with Swift, Third Edition in Packt
1 Mar 2017
Apps programmieren mit Swift in Rheinwerk Verlag
28 Oct 2016
Test-Driven iOS Development with Swift, Second Edition in Packt
22 Feb 2016
Test-Driven iOS Development with Swift, First Edition in Packt

Languages

English

Fluent

German

Native Speaker

Interests

Juggling