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Learn Swift Language Basics

Basic introduction to how to get started with the Swift Programming language, this section is focused on explaining some Swift basic syntax and concepts such as variables, constants, types and more.

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CONTENTS

@MindMansion

3 mins

Variables and Constants

Variables and Constants are two different ways we can store values in swift using the var keyword for values that we intend to update later in our code and the let keyword for values that will never change once created and initialized.

Variables

Variables var are used for storing values that will change during the life cycle of a code (while code is running). They are created with the var keyword followed by name and value.

var person = "Joe"
var age = 16

print(person)
print(age)

// Update person & age variables
person = "Mike"
age = 17

print(person)
print(age)

Constants

Unlike variables Constants are used for storing values that will NOT change while your code is running, once they are initialized they cannot be reassigned a new value somewhere in your code. They can be created with the let keyword followed by name and value.

let name = "John Doe"
let age = 23
name = "Mike Jack" // not allowed

let city: String
city = "Toronto" // initialized

Type Annotations

In Swift, we can either create a variable or constant with or without a type annotation and at the end both will yield the same result. A type annotation tells Swift compiler what kind of value you intend to store. name: type annotation => name: String

var country: String = "Canada"
var capital: String = "Ottawa"
var population21: Int = 38561490 // population as of Dec, 2021

let city: String
city = "Toronto"
Note
Notice that we rarely used type annotation in the previous examples. This is because Swift uses the power of type inference to deduce the type of variable we stored even when a type annotation is omitted. This makes it unnecessary to always include a type annotation and therefore making your code appear cleaner.

Basic Types and Type Aliasing

Basic types are types that comes bundled in swift, for storing basic values such as Int, Float, Double, Boolean, and String

Boolean

Boolean types Bool are used for storing True or False values

var isTorontoCapitalOfCanada: Bool = false
var isGameOver = 5 < 6 // True 5 is less than 6

print(isTorontoCapitalOfCanada)
print(isGameOver)

Int

Int is used for storing none decimal numbers (whole numbers) such as -14, 3800 and more. They can store hold values between -2,147,483,648 and 2,147,483,647 even on 32 bit systems.

var age: Int = 15 // with type annotation Int
var address = 501
var currentScore = -41
Tip
Though there are many other types of Integer such as Int32, Int64 (for 32 and 64, bit systems) and many others that can be used for string whole numbers, but Int is the most widely used and recommended by Swift engineers because of its ability to adapt to the native system you are building on.

Boolean

Boolean types Bool are used for storing True or False values

var isTorontoCapitalOfCanada: Bool = false
var isGameOver = 5 < 6 // True 5 is less than 6

print(isTorontoCapitalOfCanada)
print(isGameOver)

Float

Unlike Int Float is used for storing decimal numbers (numbers with fractional components) such as -412.42, 3.1415..., price, speed and more.

  • It can store numbers that are smaller or bigger than what Int can hold.
  • It represents a 32-bit floating-point numbers.
  • It has a precision of 6 decimal digits.
var price: Float = 314.0 // with type annotation Float
var speed = 75.6 // km/s

// precision limit
var floatNumber: Float = 4.1495256784785415 // Output will be limited to 6 decimal digits
print(floatNumber)
Warning
Float types can not hold decimal digits greater than 6

Double

Double is everything Float is with the exception:

  • It represents a 64-bit floating-point numbers
  • It has larger precision than Float
  • It has a precision of at least 16 decimal digits.
var price: Double = 314.0 // with type annotation Double
var speed = 75.6 // km/s

// precision limit
var doubleNumber: Double = 4.1495256784785415
print(doubleNumber)
Note
The best floating-point numbers to use depends on what you’re building but its is recommended to always use Double when not sure.

String

You may have noticed that we have used the String type to store values previously.

The String types is used for storing a string of word(s), text(s) such as name, places etc. We will talk in-depth about strings later in the series.

let name = "Mike" // inferred type String
let country: String = "Canada"

Type Alias

typealias is simply a way of saying I want a type to be something different from its original name.

i.e. in your code if we want Int to be called MagicNumber you can easily do that with typealias

You can now replace Int with MagicNumber everywhere you could have used Int

typealias MagicNumber = Int // MagicNumber can now be used as Int

let myMagicNumber: MagicNumber = 105 // annotated type `MagicNumber <= Int`
print(myMagicNumber)

Basic Operators

Operators are special signs used for performing operations such as addition, subtraction

Assignment Operator =

We have used this type of operator times in this tutorial, we use it when we want to assign a value to a variable or constant. i.e a = b or a = 4

let a = 4
var person = "Jane"

swift

basics

863 Words

SERIES

Swift Introduction

Basic introduction to Swift Programming language basics.

Swift

3mins

Learn swift language basics

3 mins