On any programming language, you would be using tons of different kinds of data types, data types is the kind of the data, in Swift it’s kind can be a string, character, integer (Int), boolean (Bool) etc. and then you may need a place in memory to store this program data. The place to store this data is called a variable.

Basic Data Types

The most basic data types are the following:

• Int for integers
• Double and Float
• Bool for boolean values
• String and Character for textual data

Variable Declaration

Simply you declare a variable starting with the reserved keyword “var” identified by a name then assign it a value using an assignment operator “=”, the value can be of any data type

var str = "Hello World"

On this example we declared a variable called “str” and assigned it a “String” type with a value of “Hello World”.

If we want to change the value, no need to start with var, you can directly assign it a new value.

str = "Goodbye"

We can declare Integers, Doubles and multiple variable declaration of different types separated by a comma

// Integer declaration
var age = 45

// Double
var x = 0.0
var y = 1.0

// multiple variables
var car = "Tesla", var hasPhone = true, var z = 1.0

Swift is smart that it inferred the data type when a value was assigned to it. Basically meaning we didn’t need to specify that data type is a string or an integer or boolean, just by the value Swift can say “Hey, this value is a string and I’ll store it as a string“.

While rare you can create a variable and provide the data type annotation if needed.

var red, green, blue : Double

On example above the multiple variables were declared of having a type of Double.