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Swift – Constants, Variables & Print function

  • Last Updated : 17 Jun, 2021

Constants and variables are those elements in a code linked with a particular type of value such as a number, a character, a string, etc. Constants once declared in a code cannot be changed. In comparison, variables can change at any time in a code within the scope.

Declaring Constants & Variables in Swift:

Constants and variables in Swift must be declared in scope before they are used. In Swift, to declare a constant, we use the “let” keyword and to declare a variable, we use the “var” keyword. Swift does not require you to end a statement with a semicolon (;).

let temp = 15

var count = 0

In general, we can declare a number of constants or variables in a single line separated by commas.

let a = 55, b = 1, c = 15

var p = 6, q = 12, r = 18

Type Annotation:

Type annotation means explicitly mentioning the type of constant or variable when declared. For example, we declare a string variable, and we haven’t initialized it yet. So, we write:

var stringName : String

Similarly, if it’s an integer, we write:



var numberTemp : Int

As we can declare several constants or variables in a single line separated by commas, if all the items are of the same type, let us say “String”, we then write:

var name, place, city: String

Naming Constants & Variables:

The naming convention may contain any character, excluding mathematical symbols, private-Unicode scalar values, arrows, and whitespace characters.

let ❤️ = “Love”
let ❤️❤️ = “more love”
var g4g = “GeeksforGeeks”

Printing Constants & Variables:

print() function:

The function in Swift to print any constant or variable value is print(_:separator:terminator:)

We declare a constant “placeName” and initialize it as a string by linking a value “Mumbai” to it. Now to print our constant, we call the print function as follows:

let placeName = “Mumbai”
print(placeName)

Output: Mumbai

String Interpolation:

String interpolation means to include a constant or a variable as a placeholder while printing and prompt Swift to replace the placeholder with the actual value of that constant or variable.

var cityName = “Mumbai”
print(“I live in \(cityName)”)

Output: I live in Mumbai
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