Christian Tietze – Software Developer

Professional Summary

Creative macOS/iOS developer with a strong focus on user experience and clean architecture. Driven by a passion for accessibility and performance, I have published six successful apps and authored three technical books and 890 blog posts. I help developers world-wide to realize their app ideas with a deep understand for the technologies.

Contact Information

• Location: Bielefeld, Germany
• GitHub: github.com/DivineDominion
• LinkedIn: linkedin.com/in/christiantietze
• Website: christiantietze.de
• Zettelkasten Blog: Zettelkasten Method

Technical Skills

Programming Languages

Swift, Objective-C, Ruby, Lisp, JavaScript, HTML, CSS, C/C++
Rust, Kotlin, Java, Python

Frameworks & Technologies

• iOS/macOS: SwiftUI, UIKit, AppKit, Core Data, Core Audio, Core Graphics, Core Text, PhotoKit, StoreKit
• Architecture: Unidirectional Data Flow (ReSwift, TCA), MVVM, VIPER, Clean Architecture, Functional Core/Imperative Shell
• Reactive: RxSwift, Combine, ReSwift
• Testing: TDD, Swift Testing, XCTest, Quick/Nimble, RSpec, Cucumber/Gherkin
• Backend: Firebase, Supabase, FastSpring e-commerce integration, PHP, Full-Stack Web Development, Apache, nginx, SQL

Tools & Platforms

Emacs, Xcode, Git, GitHub Actions, TestFlight, App Store Connect, Firebase, Docker, pjsip – and Zettelkasten as the foundational tool of all.

Professional Experience

Self-Employed App Developer & Author

2013–Present | Bielefeld, Germany

• Published 6 apps on Mac/iOS App Stores with regular updates
• Authored 3 technical books on macOS development and app distribution
• Delivered conference talks and workshops at Macoun and other developer events
• Maintain 20+ open source libraries with active community engagement

Note: All positions below were contract/freelance engagements completed part-time alongside my own app development, except where noted as employment.

iPad Developer / Technical Consultant – Ambue Ltd

March 2025–July 2025 | Contract

• Developed complex survey form app with offline-first architecture and conditional logic handling
• Implemented PhotoKit integration for efficient property photo management and compression
• Bridged communication gaps between siloed freelance team members and align technical vision with business requirements to develop an MVP now

macOS Developer – Starface

May 2023–December 2024 | Contract

• Partake in the migration from legacy AppKit to Swift/SwiftUI for enterprise VoIP client
• Built workspace designer with drag-and-drop widget placement using pure SwiftUI
• Integrated the existing SIP stack into the UI
• Modeled complex business rules and concepts for a robust migration and to reduce bugs from the legacy code-base
• Implemented reactive programming patterns using Combine and Swift Concurrency

macOS Developer – Timing

January 2020–April 2023 | Contract

• Architected comprehensive third-party integration system enabling automatic time tracking across applications for thousands of daily users
• Reverse-engineered SQLite databases to extract productivity data, creating seamless workflow integrations
• Optimized RxSwift reactive architecture for real-time activity monitoring with zero performance degradation under continuous load
• Delivered sustained improvements over 3+ years in pragmatically-tested production codebase

Project Lead & Principal Developer – “Tap Challenge” Game

August 2021–December 2023 | Contract

• Led complete project lifecycle from concept to SXSW launch for casual iOS game with zero critical bugs
• Managed cross-functional team of 3 while navigating complex agency-client relationships and proactively reducing scope for business benefit
• Architected full-stack solution using SwiftUI (iOS 15 era), Firebase real-time sync, and GDPR-compliant web portal
• Delivered modular architecture enabling event customization without code changes, supporting multiple SXSW events

Notable Projects & Products

Sorted by initial public release date.

Infinite Canvas (2025)

• Whiteboarding and sketching app with infinite zoom/pan for Mac, iPhone, and iPad
• Built with Swift, SwiftUI, and Immutable Data (unidirectional flow architecture)
• Used Claude Code for assisted programming and rapid iteration

The Archive (2018–Present)

• Knowledge management app serving thousands of daily users handling 10,000+ note collections with millisecond search performance
• Engineered sandboxed JavaScript plugin system balancing extensibility with security, enabling community-driven feature development
• Built custom MultiMarkdown C parsing for real-time rendering and proprietary indexing achieving instant full-text search at scale
• 8+ years of continuous development (v0.1 to v1.9) with community-driven roadmap and sustainable business model

TableFlip (2016–Present)

• macOS NSDocument-based visual Markdown table editor that integrates fluidly with any text editor
• Implemented extremely modular architecture
• Uses ReSwift for unidirectional data flow and functional core

Move! (2016–Present)

• macOS break reminder app promoting healthy work habits with responsive break timing
• Implements smart activity detection to ensure breaks only count when user stops working
• Built to combat health risks of prolonged sitting based on sedentary behavior research

Word Counter (2013–Present)

• Writing productivity app serving thousands of authors, journalists, and academics for 12+ years with continuous updates
• Battle-tested FastSpring integration became foundation for technical book helping developers escape 30% App Store fees
• Successfully maintained mixed Objective-C/Swift codebase through all major Swift migrations (1.0 to present)

Calendar Paste (2012–Present)

• iOS calendar companion for quickly creating recurring events and shift schedules
• Template-based event creation tool that works with the system calendar
• First commercial iOS app laying the foundation for an independent developer career

Publications

• 890 posts on this blog
• Make Money Outside the Mac App Store (2nd Edition, 2019) – Comprehensive guide to app distribution
• Exploring Mac App Development Strategies (2014) – Foundation patterns for Mac developers
• A Pattern Language for Zettelkasten (WIP)

Conference Talks & Workshops

• Macoun 2023 – Full-day Legacy Code Retreat workshop on refactoring and testing
• CocoaHeads Aachen 2022 – “Making Your App Extensible with JavaScriptCore”
• Macoun 2019 – Full-day TDD workshop: “DRY & Clean” and “Test-driven”
• Macoun 2018 – “Code Generation with Sourcery” (German)
• FastSpring Webinar 2017 – “Beyond the Mac App Store: From Code to Cash”
• Macoun 2017 – “RxReSwift – Lessons Learned” (German)
• Macoun 2016 – “Maintainable Software Architecture” (German)

Open Source

The list of individual repositories would be too long, so I’m referring GitHub organizations/teams and accounts instead:

• My personal GitHub account shows contributions, but most of my projects are organized in teams:
• GitHub team for book manuscripts and samples
• GitHub team for personal projects and private project collaborations. The latter you can’t see, though :)
• GitHub team for Zettelkasten & The Archive-related things like themes, plug-ins, and the website.

Libraries

To bootstrap a macOS app:

• WhatsNewKit: Tell users about new features in your app.
• AppGuideOverlay: Interactive tutorial to highlight parts of the UI.
• BetaExpiration: Adding visual indication about how long a beta build will continue to work. Like TestFlight, but baked into the app.
• CrashReporter: PHP server script to receive, and AppKit library to send app crash reports.
• ErrorHandling: Offering users a way to report unexpected app pathways.
• TrialLicensing: Add a time-based trial and license code-based gating of features to your app.
• Settings for macOS (co-maintainer)

User Interface Components:

• FatSidebar: Large sidebar for huge icons with drag-and-drop reordering and expand-on-hover.
• LoopingAnimation
• Omnibar and Reactive Extensions: Search/filter among a list of results, forwarding list navigation shortcuts.
• TextKitAutoCompletion: Type-to-filter auto-completion add-on to native macOS text views.
• Typewriter Modes: Keep a comfortable part of the text view in focus so that users don’t have to write at the bottom end of the screen.
• WebcamSnap: Take pictures with a camera from a Mac app.

Background services and architecture:

• DeclarativeTextKit: Express complex manipulations to NSTextView and in-memory text buffers with a declarative DSL.
• ReSwift, a Redux-inspired unidirectional data flow library. My favorite open source project of the past years because of the people and its impact. (Co-maintainer)
• RxFileMonitor: Reactive extensions to an FSEvent file system monitor.
• SearchExpressionParser: Boolean AND and OR and NOT, and parenthesized sub-expressions for search-based interfaces, for example the Omnibar UI component.
• SwiftXattrs: Access extended file attributes (xattrs).
• SwiftCSV: CSV/TSV parser for Swift (package maintainer and group admin).

Apps and Games

• md-babel: making Markdown code block executable
• TermQuickRPG: Terminal adventure game rendering in ncurses, written in Ruby.
• NowNowNow: a cross-platform /now-page reader using SwiftUI / The Composable Architecture (TCA).
• Cacti VS Llamas: a turn-based game concept.

Additional Experience

Earlier Roles

• macOS Developer Consultant – Enai (2024, 2025) – Delivered critical AppKit expertise evolving from “fighting frameworks” to leveraging platform conventions for robust architecture
• macOS Developer Consultant – fixkey.ai (2023, 2025) – Rescued AI-generated codebase by introducing sustainable architecture patterns and Core Audio integration
• macOS Developer Consultant – tapvis (2019) – Delivered FastSpring monetization ahead of schedule, proactively fixed additional bugs beyond scope (client testimonial available)
• iOS Developer – ADinfinitum Inc. (2019) – Sub-contracted iOS app development
• iOS Library Developer – ObjectBox (2018) [Employment] – Created Objective-C++ wrapper and Swift API for NoSQL database
• iOS Developer – Chef.One (2016-2017) – Developed iOS app for social dining platform startup

Other Professional Experience

• Peer Tutor – Bielefeld University “Peer Learning” (2011-2018) – Coordinated educational workshops and provided 1:1 coaching for hundreds of students
• IT Support & Web Developer – Department of Philosophy, Bielefeld University (2012-2014)
• Student Assistant – Bielefeld University (2011-2012)
• Freelance Graphics Artist – Softgames (2004-2005) – Created pixel art for J2ME mobile games
• Front-end Web Developer Intern – elephantseven (2004) – TYPO3 development and UI planning
• Military Service – German Armed Forces (2007-2008) – Office administration, rank: Hauptgefreiter

Education

• Bachelor’s Degree – Philosophy & Computer Science, Bielefeld University, Germany (2008-Present)
• Abitur – A-levels in Physics, Mathematics, Philosophy, and German (2007)
• Applied Computer Science – Part-time classes at FHDW Gütersloh (2005-2006)

Current projects and availability | Detailed project portfolio