My First iOS App: A Dual Stopwatch for My Daughters ⏱👧👧

For a while, I wanted a simple way to track my two daughters’ exercise times. I couldn’t find an ad-free app that did exactly what I needed:

✔ Two independent stopwatches
✔ On the same screen
✔ Start/pause/reset separately

So I decided to use this opportunity to create my very first iOS app.

💡 Concept

The idea was small but meaningful: two colorful timers for two amazing girls.

I named it KidsStopwatch, and built it using SwiftUI.

🛠 Development Setup

I started with: MacBook + macOS, Xcode 26, SwiftUI, and a Personal Team (free Apple Developer Account).
The UI is simple: two large timers (one per kid), start/pause buttons, and a reset button.

😅 The Journey — Debugging Code Signing

Building the app was straightforward with the help of ChatGPT. Deploying to the iOS Simulator was a breeze 🚀
However, deploying to my real iPhone was not 😂.

I connected my iPhone, pressed ▶️ to install… and everything broke 😅

💥 The Error That Started It All

Xcode repeatedly showed:

Command CodeSign failed with a nonzero exit code
errSecInternalComponent

🚫 No app installation
🚫 No “Trust this developer” section in iPhone settings
🚫 Couldn’t register device in Personal Team
🚫 Couldn’t manually manage certificates

This error is notoriously vague — could mean keychain issues, missing profiles, developer permissions… anything.

🔍 Complete Debugging Timeline

Here’s every step I tried — many are required if you have a fresh free developer setup.

1️⃣ Enable Developer Mode on iPhone

Settings → Privacy & Security → Developer Mode

Restart iPhone and turn Developer Mode ON

2️⃣ Reset iPhone Developer Trust State

Settings → General → Transfer or Reset iPhone
       → Reset → Reset Location & Privacy

Reconnect → Tap Trust This Computer

3️⃣ Reset Signing Artifacts

Remove stale profiles and build data:

rm -rf ~/Library/MobileDevice/Provisioning\ Profiles/*
rm -rf ~/Library/Developer/Xcode/DerivedData/*

4️⃣ Fix macOS Developer Services (THIS STEP WAS CRITICAL)

This finally resolved the CodeSign internal failures:

sudo DevToolsSecurity --enable
sudo /usr/sbin/DevToolsSecurity -enable
sudo security authorizationdb write system.privilege.taskport allow
sudo killall -9 trustd

✔ Re-enabled macOS developer authentication
✔ Reset trust agent for signing identity access

(This was the turning point!)

5️⃣ Recreate Certificates in Xcode

In Xcode:

Xcode → Settings → Accounts → Manage Certificates…

Delete anything broken → then click:

+ → Apple Development

A working signing identity appears 🎉

6️⃣ Toggle Project Signing

TARGET → Signing & Capabilities:
✔ Automatically manage signing
Team: Yang Feng (Personal Team)
Bundle ID: com.yangfeng.ksw3 (must be unique)

This generates a fresh provisioning profile.

7️⃣ Pair Device Properly

Window → Devices and Simulators

Make sure:

• Device is shown as Paired
• macOS Keychain pop‑ups → Always Allow

8️⃣ Press ▶️ and Watch the Prompts

You’ll see:

Trust here:

Settings → General → VPN & Device Management → Developer App → Trust

🚀 SUCCESS!!

🎉 The KidsStopwatch app launched.

Key takeaways:
✨ Xcode + SwiftUI are friendly starting points
😤 Code signing can be painful on a fresh Personal Team setup
💡 Resetting macOS developer services and recreating certificates was the turning point
💪 Persistence (and clear prompts) pay off

I proudly watched my own app running on my own phone for the first time.
My daughters were even more excited than I was 😄

Thanks for reading — and feel free to reach out if you’re also building your first iOS app!