Before Writing a Single Line of Code — Planning My Gym App🏋️

Hey fellow devs, 👋

Moving on from AI chaos, this time it's all about learning something new.

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💡 What I'm Building

I'm building a simple gym schedule app — entirely with the help of Claude.

The app lets users set a weekly schedule from Monday to Sunday, with their gym
timings, workout split, exercises, reps and sets. Nothing fancy — this is purely
a practice project. But the plan is to build it right, not just fast.

Since vibe coding is clearly the future, getting comfortable with it early felt
like a smart move. 🚀

📊 Sequence Diagrams — What Even Are They?

A sequence diagram maps out how different parts of a system interact with each
other in a specific order over time.

Think of it like a WhatsApp conversation — you can see exactly who said what, to whom, and in what order.

Here's the sequence diagram I made for my app:

🧠 How I Actually Built It

The first step is identifying your actors — the objects that interact with
the system. For my app this was straightforward:

• The User — inputs the schedule
• The UI — handles what the user sees and does
• The Database — saves and retrieves the data

Simple enough. But here's where it gets interesting.

Good developers don't just map out the ideal scenario. They think about
everything that could go wrong. Because it's an imperfect world.

For example — what happens if the user tries to save a workout day without
filling in all the fields? No exercises, no reps, just an empty entry hitting
the database. The diagram needs to account for that validation step, otherwise
that's a bug waiting to happen from day one.

Thinking about failure early is what separates planned apps from messy ones.

🗺️ Why Planning Actually Matters

Jumping straight into code is tempting. I get it.

But mapping the flow first forces you to ask questions you'd otherwise miss —
Is this feature actually necessary? What happens if this step fails? Does this
even make sense?

In a small project like this it keeps things clean. In larger projects, it can
save weeks of rework. The planning stage is unglamorous but it's genuinely
important.

🤖 Claude's Role — Plan Mode

Claude is brilliant at building apps, but even Claude isn't perfect — and
usually when something goes wrong, it's because the prompt wasn't clear enough.
That's on the user, not Claude.

So before touching any code, I sent Claude my sequence diagram and we
brainstormed the entire app structure together in plan mode — no building,
just thinking. Getting Claude to deeply understand what I want before it starts
writing anything makes the whole process cleaner and faster.

Context first, code later. ✨

Next up — enough planning, time to actually build something. See you there. 👀