The differences between variables and constants

Probably, the most often used feature in all programming languages is creating and storing a value. We create local variables in functions and declare them in classes and other data structures; that's why it's very important to do it properly.

In Swift, there are two ways of creating and storing a value, as follows:

• Making it a variable:

  var name = "Sara"

• Making it a constant:

  let name = "Sara"

The difference between variables and constants is that a constant value can be assigned only once and can't be changed after that. A variable value, on the other hand, can be changed anytime. Here's an example:

var name = "Sam"
name = "Jon"

let lastName = "Peterson"
lastName = "Jakson" //Error, can't change constant after assigning

Tip

The golden rule is to always declare your type as a constant (the let keyword in the previous example) first. Change it to a variable (the var keyword) only if you need it afterwards.

There are some exceptions when you can't declare...