Swift Inheritance and extension

Inherit & extension inheritance and extension

Parent class

Class Car {

var speed = 0

var Description: String {

Return "mph" (speed) km/h

}

Func sound () {

}

}

Let a car = car ()

A car. Description

Subclass Inherits Parent Class

Class Bike: Car {

var has basket = False

}

Let a bike = bicycle ()

A bike. There is a basket = True

a bike. Speed = 25

A bike. Description

Subclasses of subclasses

Class couple bike: Bike {

var current number of passengers = 0

}

Let a couple bike = couple bike ()

A couple bike. Speed = 20

A couple bike. Description

Methods for subclasses overloading parent classes

Class bullet train: Car {

Override Func beep () {

println ("Toot Toot")

}

}

Let a bullet train = car ()

A bullet train. Sound ()

The subclass overloads the computed properties of the parent class

Class Car: Car {

Override var speed = 60

Number of var wheels = 0

Override var Description: string{

Return super. Description + ", have \ (number of wheels) of wheels"

}

Override var speed: int{

Didset {

If speed > 120 {

println ("Warning: You are speeding")

}

}

}

}

Let a car = car ()

A car. Speed = 121

A car. Number of wheels = 4

A car. Description

Extension (equivalent to classification)

The class/struct/enum type that already exists. Typically used to

1. Source code agnostic situation

2. Decomposition of complex classes to improve maintainability

Extension Double {

var rmb:double{

return self * 0.0597

}

}

31_4150.rmb

Integer self squared

Extension Int {

mutating func squared () {

Self *= Self

}

}

var an integer = 1024

An integer. Square ()

An integer

Swift Inheritance and extension