Build iOS App with AI Assisted Coding

Calvin,•3 min read
ai
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Challenge: build an iOS app with the help of GPT and GitHub Copilot in two days.

I have pretty much zero knowledge coding native iOS apps in Swift. My only experience dealing with app developmnet is using React Native.

My goal is to build an iOS + Watch app that, when the iOS device is physically moved or picked up, immediately sends a message to my paired watch to alert me. I got this idea when I went to a local swimming pool. I often leave my phone in the backpack, put it on an open shelf, and go swimming. I want to know if anyone tries to take my backpack.

Here are the steps I took to build the app.

  1. Start a new Xcode project using “WatchOS” template -> Watch App with New Companion iOS App.

  2. Ask ChatGPT with this prompt: "Write a simple iOS project. The goal is to use iPhone motion sensor to detect movement of the phone. If a movement is detected, send a notification to a paired apple watch."

  3. I got some code from the answer, while gives me a basic idea of the library and commands that can detect motion with the accelerometer. However, I realized that the code is using an older coding style AppDelegate, which is not used in the new project generated by the template. I am using Xcode 14.3.

  4. Also, I found it too clumbersome to copy & paste between the chat.openai.com browser tab and the Xcode. So I opened the project directory with VScode, and installed the extension DanielSanMedium.dscodegpt

  5. The extension is quite convenient. I can highlight part the code, and then ask GPT questions regarding the selected lines of code. Also, I can also GPT to improve, find problems, and document the selected code.

  6. I also wanted to try GitHub Copilot. Unlike the CodeGPT extension, the default way to use GitHub Copilot is to create functions. It is not as versatile.

  7. I found that there are basically 2 ways to pass message from iOS app to Watch:

    • Local push notification - this is the original way I imagined. I wanted the watch app to stay in the background while I swim, with the Fitness app tracking my swimming data. But later on I found that by default if the companion iOS app is in the foreground, push notification will be displayed there rather than on the watch. Furthermore, if I want the iOS app to be run on the background detecting motion, I will need to jump through more hoops and get background capabilities.
    • WatchConnectivity session - only work when both iOS and Watch apps are in the foreground. For this experiment I think this is good enough.

  8. Unfortunately, neither CodeGPT nor Copilot could give me a working code snippet for the WatchConnectivity session. So I went back to the basic: Google. After a few pages, I found this article: Sending Data Between watchOS and iOS App Using Watch Connectivity by Baha Abisheva that can quickly get the result I want.

  9. Tada! The app is working! See the project in GitHub: 👉 https://github.com/calvincchan/PhoneWatcher

Learnings

  1. Assisted coding is not super robust at the moment, but the development will be accelerated. It is only getting better and better.

  2. Human vetting is still necessary.

  3. “Explain the selected code” and “Check of mistakes” are super useful to spot common mistakes. It also helped me to check the Swift code that I am not familiar with.

  4. Yet to try the “Create unit tests” feature in CodeGPT. I will test it in other projects.

It is a good experiment to get something working in an unfamiliar programming language. Next, I will try to use these tools on existing projects in programming languages I am familiar with.