Katsumi Kishikawa
IOS Developer at Open Source Developer
Tokyo, Japan
Summary
🤩
Rockstar🎓
Top SchoolKatsumi Kishikawa is a seasoned iOS developer with 17+ years building native iPhone and Mac applications, developer tools, and reusable libraries while actively maintaining popular open-source projects. Based in Tokyo, he combines deep expertise in CoreText, JavaScriptCore, CoreData and the Objective-C runtime with fluency in Swift, Objective-C and C/C++, enabling high-quality text, UI and database work across platforms including watchOS and tvOS. He has significant open-source impact—authoring widely used libraries like KeychainAccess and SpreadsheetView and contributing core fixes and build tooling to Realm. Beyond shipping apps, he focuses on developer ergonomics: backports, AST visualizers, CI improvements and test automation to raise code quality. Regular conference speaker on low-level topics like linking and AST meta-programming, he blends systems-level insight with practical UX improvements.
17 years of coding experience
17 years of employment as a software developer
Bachelor, Japanese Literature, Bachelor, Japanese Literature at Kobe University
Stackoverflow
10,503reputation
460kreached
215answers
0questions
xcode
top-5%
ios
top-1%
realm
top-1%
migration
top-5%
objective-c
top-5%
swift
top-1%
Github Skills (49)
unit-testing10
objective-c10
ios10
c-language10
porting10
image-processing10
testing10
databases10
bitcoin10
bitcoins10
ui-design10
coretext10
xctest10
security10
portable-database10
Programming languages (16)
Github contributions (5)
kishikawakatsumi/IBPCollectionViewCompositionalLayout
Aug 2019 - Feb 2021
Backport of UICollectionViewCompositionalLayout to earlier iOS 12
Role in this project:
iOS Mobile Developer
iOS Mobile DeveloperContributions:25 releases, 271 commits, 208 PRs in 1 year 6 months
Contributions summary:Katsumi primarily contributed to backporting UICollectionViewCompositionalLayout to earlier iOS versions, enhancing the functionality of the original library. Their commits focused on fixing build failures and typos, and adding support for features like orthogonal scrolling, content insets, and decoration views. Furthermore, the user updated the project to use the latest UIKit APIs and also added compatibility with Swift Package Manager, making the library a more accessible and drop-in replacement.
backportuicollectionviewcompositionallayoutuicollectionviewlayoutcompositional-layoutsswift
bannzai/SpreadsheetView
May 2017 - Jun 2019
Full configurable spreadsheet view user interfaces for iOS applications. With this framework, you can easily create complex layouts like schedule, gantt chart or timetable as if you are using Excel.
Role in this project:Mobile Developer (iOS) & QA Engineer / Test Automation Engineer
Mobile Developer (iOS) & QA Engineer / Test Automation EngineerContributions:14 releases, 248 commits, 196 PRs in 2 years 1 month
Contributions summary:Katsumi primarily focused on improving the quality and reliability of the iOS spreadsheet view framework through testing and bug fixes. Their contributions included addressing CI/CD related issues, such as timeout problems, and optimizing test scripts. They also added features like convenience initializers and corrected functionality related to scrolling and merged cells, improving the framework's overall usability and correctness. The user's work also involved adding unit tests to improve test coverage.
configurablechartgrid-layoutlayoutsuser-interfaces
Find and Hire Top DevelopersWe’ve analyzed the programming source code of over 60 million software developers on GitHub and scored them by 50,000 skills. Sign-up on Prog,AI to search for software developers.