Variables & constants in Swift is a basic and fundamental concept. This tutorial is focusing on explaining let(immutable) & var(mutable) declaration. Both variable and constant two terms are self-explanatory, Constant refers to the values which never gets changed during runtime. Whereas Variable refers to the values, which can be changed during runtime.
Declaring a Constant:
let is the keyword, used to declare the constants.
let myName = “ABCD” and let age = 20
var is the keyword , used to declare the variables.
var salary= 2000;
You can change the value of this salary variable since it is declared with var keyword. whereas you can’t change the age since it is declared with let keyword.
salary = 3000 // works fine
age = 22 // compile error
Note: Though it is not mandatory to terminate the line with a semicolon in swift. You can use semicolon to write multiple lines in single line . ex let a = 90; var b = 100
We will see variables & constants in detail in data type & Tuples