Show HN: I built an open-source workout tracker app in 4 days with Claude Code

Hey HN! I just built an iOS weight lifting logger app for myself. I mainly built it to learn how to use Claude Code and iOS development. Now I am learning what to do now that I have built it! I am a recent CS grad (so an entry level SWE) and I come from a fullstack and robotics dev background. Made a mobile app using Flutter in HS but never did any iOS development.

Quick Blurb: I built the app as a better version of Apple Notes but a simpler version of the full-featured workout logging apps. I wanted this app to be super simple, just log workouts in the least amount of clicks and show the data while having an amazing watch interface.

Testflight: https://testflight.apple.com/join/mAfE5kJD Github link: https://github.com/randomlylelo/curlsapp

Here are some of the lessons I learned from using Claude Code:

- Agents are powerful, but the best way to use them is to be ultra-specific and do it per project. The general repos are quite useless. I made a iOS developer agent and it was super powerful: https://github.com/randomlylelo/curlsapp/blob/main/.claude/a...

    - I initially used it to help add animation to all my screens and make everything consistent in my code. The commit is here: https://github.com/randomlylelo/curlsapp/commit/524fd65dac6d3534bd5862b91e3f7d507803e030

        - It broke one of my screens but it was a simple fix.

    - I used it whenever I had a difficult feature. It worked better than just 'ultrathink', it did use more tokens though.

- It is quite useful in learning and exposing concepts. I used it to expose me to iOS app patterns. I ended up using a weird combo for the design, but I put the description of the new structure in Claude.md. Then the agents and Claude Code was able to build to this new structure.

- While using Claude Code, I could prompt it with a feature I would want, while it was building it, I would think about the next feature, then come back to it once it finished building. I was doing this sequentially and was able to spend a lot of my time thinking about the design. I was pretty specific in drafting my prompts and ideas before.

This is my current experience with Claude Code and I would love to hear your thoughts on my app / code / experience with Claude Code. If you are an iOS dev, I would love learning from you.

I am still working polishing the app so I can use it everyday but wanted to publish something first :). The apple watch integration will be worked on next.

Note: My initial version took about 4 days, then I took a break to go through the App Store process. I tried to keep the code as clean as possible but I think I do need to refactor it manually soon. I have been working out and using it myself.