Variable Naming Rules in Scala in Scala

TL ; DR:

• In Scala, we use the camelCase convention to name our variables. It implies separating different words with capital letters, like this:

  val companyName = "Apple"
  
  val foundingYear = 1976
  
  val isUnicorn = true
  
  val numberOfEmployees = 137000
  

  
  

Full lesson:

Variable names must consist ONLY of letters, numbers and underscores and they must start with a letter or underscore.

Bad variable names:

val 18spam = 1
val x.15 = "hello"
val #name = true

If you try to create a variable with any of these names, Scala will throw an error.

Naming conventions: camelCase and snake_case

Sometimes a variable name might consist of multiple words, for example if you want to store the first name of a person. You might be tempted to separate those names by whitespaces, like this:

val first name = "Kate"

This code will also throw an error.

When you name your variables, you want to use one of these two conventions:

snake_case = separate different words with an underscore (_), like this:

val first_name = "Jane"
val last_name = "Doe"

camelCase = separate different words with capital letters, like this:

val firstName = "Jane"
val lastName = "Doe"

It's important to be consistent with the casing technique you use. Do not combine both of them in the same code, like this:

val first_name = "Jane"
val lastName = "Doe"

Case sensitive:

Variable names are case sensitive:

val name = "Kate"
val Name = "Andy"
val NAME = "George"

println(name + " " + Name + " " + NAME) // Output: Kate Andy George

Although Scala allows us to do this, it's always confusing and a bad coding practice to differentiate variable names just by case!

Mnemonic Variable Names:

Since we programmers are given a choice in how we choose our variable names, there is a bit of "best practice".

Sometimes we want them short like x and y, but sometimes we want them descriptive, especially if they are important.

Here is a great example:

val a = 25
val b = 13
val c = a * b
println(c)

compared to:

val hours = 25
val rate = 13
val pay = hours * rate
println(pay)

Scala understands and is happy with both of these pieces of code. But it's clearly which version makes your reader happier.