Variables II: Naming

Previous chapter introduced you to the wonderful world of giving names to everything. But can you use any name for your variable? The answer is no, but it’s close.

The same key rules exist in all programming languages. Because they are a direct result of how a computer works.

How does it know you’re typing variable? And not a calculation? Or a number? Or one of those keywords (like say)?

It can only decipher this (quickly) by establishing a few rules. Variables can’t …

• … start with a number. (But can use them later on.)
• … contain a special symbol, like a space. (Some languages might have a few exceptions.)
• … be named exactly like an existing keyword. (Try it. Try creating a variable named “say”.)

This is how the computer knows the difference between “this text is a variable” and “this text is something else”.

In general, just use regular letters (lowercase or uppercase) and you’re fine.

Cases

But if you can’t add spaces, how do you keep things readable? We often want multiple words or parts in our variable names.

For this, we invented several different “cases”.

• camelCase = capitalize every word except the first
• PascalCase = capitalize every word
• snake_case = add an underscore (_) between words, all lowercase
• kebab-case = add a dash (-) between words, all lowercase

The last one is rare, as the minus sign is usually reserved for subtraction. For my language, I thought camelCase was the best, so that’s what my examples use.

In practice

Once named, you can use your variable everywhere and however you want. As you saw in the examples, whenever we type the name again, it recognized it. The computer just grabs its current value and uses that.

What does this mean for the practical world? How would you use variables?

In this course, I also want to nudge you towards good programming habits. That’s why I’m telling you this now:

Naming variables is the most important skill in coding

Or one of the most important. I mean that in all seriousness.

Think back to the analogy. If your code is filled with jars labeled “Butterfly” while they could actually contain any other insect, your code will crash and burn. Working on it becomes a confusing chore. What is where? What’s the latest value of this one thing?

You might say: “well then, I’ll just give everything a generic name!” All jars are labeled “insect”.

The computer can only have one jar called insect. Each variable name can only appear once. When re-used, it overwrites the previous value. So what, you’re going to call them “insect1”, “insect2”, and so on?

Now you might say: “well then, I’ll give everything an extremely specific name!” This jar is called “Butterfly with red wings and long antennas caught on September 3rd”.

I wish you good luck writing that in camelCase—every single usage 😉

As usual, the solution is down the middle.

Use many variables that say—in one to three words—exactly what they contain.

Example: bad

Let’s do an exercise. Look at the code below. The variables have short names with simple English words. Nice, right? But do you have any idea what the data actually means?

Two Numbers

 => 

Number

Now I’ll explain the context. This code is for an online multiplayer game. Each game is played on a new server with a group of 4 players: 2 versus 2.

The problem it tries to solve: how many servers do we need to keep online?

Without my explanation, you’d have never known this. Updating the code—when new problems arise—is impossible.

Example: better

Try to rewrite this. Try to make the variables specific and meaningful, but not overly long.

Whenever I give you a challenge (or “exercise”), I’ll provide an empty code field and my solution below it. The solution, however, is hidden so you’re less tempted to peek 😉 Click it to unfold it. Do remember that I give my solution, but there are many ways to solve any problem.

As you code more, you’ll create your own shorthands. Like num for number. Or ev for event. As long as they are clear and unique, that’s a good idea.

Naming variables also depends on personal preference or your project. For example, you might change the first variable to numPlayersOnline if your game also supports offline.

It’s easy to accidentally steer the wrong way here.

Be as specific as needed, but not more.

Now, if you change the number of players to, say, 10, your code will run fine. But the output is actually bad. How do you activate … 2 and a half server?

Next chapters talk about common keywords for manipulating data even further. Such as rounding that sad half server to a whole one!