Variable Naming Rules in Swift in Swift

TL ; DR:

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

  let companyName = "Apple"
  
  let foundingYear = 1976
  
  let isUnicorn = true
  
  let 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:

let 18spam: Int
let x.15: String
let #name: Bool

If you try to create a variable with any of these names, Swift 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:

let 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:

let first_name = "Jane"
let last_name = "Doe"

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

let firstName = "Jane"
let 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:

let first_name = "Jane"
let lastName = "Doe"

Case sensitive:

Variable names are case sensitive:

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

print(name, Name, NAME) // Output: Kate Andy George

Although Swift 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:

let a = 25
let b = 13
let c = a * b
print(c)

compared to:

let hours = 25
let rate = 13
let pay = hours * rate
print(pay)

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