Work

Here’s an overview of my work and areas of expertise, spanning my Mac app Diagrams, freelance client projects, and open-source libraries.

Skills

• AppKit: My entry point into Apple development and still my go-to framework for building Mac apps.
• SwiftUI: Adopted from the start, comfortable with the declarative model, advanced concepts, and bridging to older frameworks.
• UIKit: A mature framework I reach for when building polished iOS apps, especially where SwiftUI falls short.
• Combine: A long-time FRP proponent, previously using ReactiveSwift and now fluent in Apple’s first-party framework.
• Swift Concurrency: Solid understanding of Swift’s modern concurrency model and its tools. This ain’t easy, so definitely still learning.
• TCA: Drawn to its Redux-inspired approach to app architecture, a natural fit for how I like to structure code.
• SQLiteData: Another of Point-Free’s libraries, becoming my go-to persistence solution.
• CloudKit & Sync: Comfortable with Apple’s native sync service and strategies for implementing sync correctly, including offline support, conflict resolution, and sharing.
• Reverse Engineering: Passionate about diving into Apple’s frameworks to understand, extend, or work around their behavior.
• Agentic Coding: Working with Claude Code in my daily workflow to boost my productivity, relying on years of hands-on experience to keep its output in check.
• UX Design: Not a designer, but something I care deeply about and have a strong eye for making it feel right.

Projects

Diagrams

diagrams.app Founder & Developer Structured Path GmbH Nov 2017 – present

• A native, document-based diagram editor for Mac I created, owning product vision, architecture, and development.
• Swift / AppKit / SwiftUI / ReactiveSwift / MVVM / Redux
• Architected around a custom Redux-based layer for managing document state with advanced undo support, paired with MVVM in the UI layer.
• Built a custom canvas rendering stack driven by a declarative DSL for describing canvas content, conceptually similar to SwiftUI but predating it.
• Developed an interaction engine on top, handling mouse/keyboard events and supporting an infinite canvas, smart grid layout, and advanced relationship routing.
• Designed a palette system for defining reusable element and relationship types, with built-in presets for common domains.
• Implemented a custom document format with an intermediate serialization layer and versioned migrations.
• Built a StoreKit-based activation flow with a custom free trial, in-app purchase handling, and receipt validation.
• Implemented system integrations including Quick Look previews and thumbnails, Shortcut automation, and PDF/image export.
• Localized into three languages (English, German, Chinese).
• Distributed on the Mac App Store and Setapp.
• Collaborated with business mentor Ronald Scholz and designer Alex Käßner, who created the app’s visual identity and designed the UI.

Tower

git-tower.com Developer, Freelance SaaS.group GmbH Oct 2022 – Jun 2023

• Contributed to select subcomponents of a well-established Git client for Mac.
• Swift / SwiftUI / AppKit / Combine
• Modernized two features originally built in AppKit / Objective-C / XIB by rebuilding them in SwiftUI. For each, first built a standalone prototype to validate the approach, then integrated it into the main codebase.
• Rebuilt the merge wizard for resolving various kinds of Git file conflicts, revamping the UI for modern macOS design language.
• Rebuilt the onboarding flow, a complex multi-screen experience handling trial registration, license activation, and initial app setup.
• Worked largely independently, aligning with the team on requirements and integration points.

Ambue

ambue.com Developer, Freelance Ambue Ltd May 2024 – Jun 2025

• A newly developed iPad app for property surveying at a UK-based retrofitting company, designed for an offline-first workflow to ensure reliable use without connectivity on-site.
• Responsible for gathering requirements, designing UI/UX concepts, and handling the full development.
• Swift / SwiftUI / TCA
• Developed a generic survey template system, enabling various survey kinds to be authored outside the app using a hierarchical structure (pages, sections, subsections, fields), with additional domain-specific grouping into stories and rooms. Introduced entities to represent multiple instances of items (e.g. walls, windows).
• Implemented conditional logic, evaluating template-defined rules against in-progress survey data.
• Started with a Swift-based DSL, then laid the groundwork for JSON-based templates with a custom schema and versioning strategy to support evolution.
• Built custom SwiftUI field controls optimized for on-site input, supporting numeric, text, date, single/multiple select, image and entity collection fields—with clear indication of missing values and values pending confirmation.
• Worked independently for most of the project and was joined by Christian Tietze in the final phase.
• The screenshots above show a demo survey designed to showcase all features of the system, rather than a specific survey kind used by the client.

Dupes

cfloinc.com Lead Developer, Freelance cflo inc. Feb 2024 – present

• A Mac app for clearing duplicate tracks in Serato DJ libraries.
• Built the app from scratch, owning the architecture and full implementation.
• Swift / AppKit / SwiftUI / Combine / Swift Concurrency / MVVM
• Implemented UI based on the design spec, including interactive matching strategy selection and results presentation in a highly customized NSTableView.
• Implemented duplicate detection logic for identifying and grouping tracks based on configurable matching strategies.
• Reverse-engineered Serato DJ library formats and built a framework providing read/write access to track, crate, and preference data.
• Built a reusable foundation for the client’s app suite, bundling libraries for licensing, permissions, shared UI, and Apple framework extensions.
• Designed the licensing stack (server-validated activation, device linking, offline grace period, reactivation), with a companion UI package covering welcome and license-management flows.
• Implemented a Sparkle-based multi-channel release pipeline supporting dynamic feed selection.
• Worked closely with Kyle Halevi, the designer behind the app’s UI.

Open Source

I occasionally publish open-source libraries on GitHub. Here are some current highlights:

• InterposeKit: A revamp of Peter Steinberger’s method swizzling library with nice Swift API.
• swift-mrdt: Three-way merging of concurrent changes to collection data types.
• CombineExtensions: A CurrentValuePublisher type and additional operators for Combine.
• SettingsRepository: A lightweight, type-safe, and extensible settings system for Swift apps.

Let’s Talk

I’m always open to new freelance engagements on iOS and macOS projects, whether that means owning an app end-to-end, contributing to a specific subcomponent, or jumping in for focused consulting. If that sounds like a fit, drop me a line.