Published by Arunprasadh C on 21 Apr 2022 • Last Updated on 06 May 2022

Variables, Literals and Constants in Swift

Literals

Literals are used to represent data values like Int or any other Data Type value in the Source Code.

Example :

45 // Int Literal
"Hello World" // String Literal
3.14 // Floating-point Literal

We can assign values to Variables and Constants by means if Literals.

Variables

In the previous Topic Pages, you would have seen the word “Variable” in many places. In fact, it is quite hard to write a program without using variables. Why is it so ? It is so because, a Variable as its name suggests, is used for storing a named variable value (value that can be changed). In Swift, variables can be declared by using var Keyword.

Example :

var a = 45 // Statement 1
var b: String = "Hello" // Statement 2

As we saw in the Previous Topic, Swift can infer the Data Type of variable using the assigned Literal. This kind of declaration is used in Statement 1 above. On the other hand, in Statement 2, the Data Type of the Variable is explicitly specified in the Declaration. This kind of explicit Type Specification is called as Type Annotation in Swift. The general syntax of Type Annotation is as shown below:

var variableName:<data type> = <optional initial value>

Type Annotation is not compulsory in Swift as Data Types are inferred automatically. Usually, Type Annotations are used for enhancing the readability of the code. Type Annotations also allow the variables to be declared without any initial value. These variables can be assigned with value in the later part of the code.

Example :

var word:String
// Some statements
word = "Hello"

Defining Multiple Variables on a single line

Multiple variables can be declared/defined with/without initialization in a single line provided that the variables are annotated with their types.

Syntax :

var v1:DataType1 = optInitialValue1, v2:DataType2 = optInitialValue1, v3:DataType3 = optInitialValue1, ...

Example :

var name: String = "Kris", age: Int = 22, native: String = "Chennai"
print("\(name), who is \(age) years old, is from \(native).")

Output :

Kris, who is 22 years old, is from Chennai.

Initializing/Assigning values to Multiple Variables using Tuple Syntax

Multiple variables can be reassigned to values at once using the Tuple Syntax:

Syntax :

(v1, v2, v3, ...) = (value1, value2, value3, ...)

Example : Consider the variables declared in the previous example

(name, age, native) = ("Kris", 21, "Madras")
native = "Chennai"
print("\(name) is a \(age) year old boy whose native is \(native)")

Output :

Kris is a 21 year old boy whose native is Chennai

Constants

Constants can be considered as Immutable (or read-only) Variables. Constants allow the values to be assigned only once. After assignment, the value can’t be changed. It can only be accessed. In Swift, constants can be declared by using let Keyword. The general syntax of declaring constants is as follows:

let constantName = <initial value>

Example :

let pi = 3.14 // CONSTANT
var radius = 7 // VARIABLE
var area = pi*radius*radius // VARIABLE

As with variables, Type Annotations can also be used with Constants in Swift (Simply replace var with let). Also, like variables, many constants can also be declared at once in a single line and be can initialized using tuple syntax.

The next Topic will cover about Basic I/O Functions in Swift.

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