Documentation Series of Swift

Part 1 — The Basics of Swift

In this article will cover the very basics of Swift

Constants and Variables

To define variable we can use let and var

let — it’s value can never be changed

let maximumNumber = 10
let languageName = "Swift"
languageName = "Swift++"
// This is a compile-time error: languageName cannot be changed.

var — it’s value can be changed

var friendlyWelcome = "Hello!"
friendlyWelcome = "Bonjour!"
// friendlyWelcome is now "Bonjour!"

Types of annotations

It is providing types to the variable or constant while defining it.

var welcomeMessage: String

Defining multiple related variables

var red, green, blue: Double

Naming constants and variables

Constant and variable names can’t contain whitespace characters, mathematical symbols, arrows, private-use Unicode scalar values, or line- and box-drawing characters. Nor can they begin with a number, although numbers may be included elsewhere within the name.

var Welcome = "Hello"
print("\(Welcome) Nafish")

Comments

To write Single line comment use // …..

//.........

To write multiple line comment use / ..… /

/* .............
..............*/

Semicolons

We don’t need to use any Semicolon after each statement but you can use it to write multiple statements in single line like

let cat = "Luna"; print(cat)

Integers

Integers are whole numbers with no fractional component, such as 42 and -23. Integers are either signed (positive, zero, or negative) or unsigned (positive or zero).

let Number: Int = 3

Floating-Point Numbers

Floating point numbers have a fractional component, such as 3.14159, 0.1, and -273.15.

let Number: Float = 3.123

Integer and floating-point conversion

You can convert int to float by following ways

let three = 3
let pointOneFour = 0.14
let pi = Double(three) + pointOnefour

Boolean

It is called as Bool, it has two values True and False mostly useful for conditional statements.

Tuples

It can contain multiple types of values in single tuple

let httpError = (404, "Not Found")

Where 404 in int and Not Found is String.

You can name the individual elements in tuple like

let http200Status = (statusCode: 200, description: "OK")
print(http200Status.statusCode)

Optionals

It represents a variable that can either have a value or can be nil

let Number : Int? = 124

Force Unwrapping (!) we can use ! to unwrap to the end of optional name,when you force unwrap a non-nil value, the result is its unwrapped value.

Error Handling

We use error handling to respond to error conditions.

func canThroughError() throws{

}

Assertions and Preconditions

We use these to make sure essential conditions is satisfied before executing code.