Why inheritance is class-only in Swift - See It in Action

Why inheritance is class-only in Swift

📖 Scenario: Imagine you are building a simple app to manage different types of vehicles. You want to share common features like speed and capacity but also have specific features for cars and bicycles.

🎯 Goal: Learn why inheritance in Swift works only with classes and not with structs or enums by creating a simple class hierarchy.

📋 What You'll Learn

Create a base class called Vehicle with properties speed and capacity

Create a subclass called Car that inherits from Vehicle and adds a property brand

Create a subclass called Bicycle that inherits from Vehicle and adds a property hasBasket

Print details of a Car and a Bicycle instance

💡 Why This Matters

🌍 Real World

Inheritance helps organize code when building apps with related objects like vehicles, animals, or UI elements.

💼 Career

Understanding class-only inheritance is important for Swift developers to design clean, reusable, and maintainable code.

1

Create the base class Vehicle

Create a class called Vehicle with two properties: speed of type Int and capacity of type Int. Initialize both properties in an initializer.

Swift

class Vehicle {
    // Your code here
}

Need a hint?

Use class keyword to define a class. Add properties and an initializer method.

2

Create subclass Car inheriting from Vehicle

Create a class called Car that inherits from Vehicle. Add a property brand of type String. Create an initializer that takes speed, capacity, and brand and calls the superclass initializer for speed and capacity.

Swift

class Vehicle {
    var speed: Int
    var capacity: Int
    
    init(speed: Int, capacity: Int) {
        self.speed = speed
        self.capacity = capacity
    }
}

// Your code here

Need a hint?

Use class Car: Vehicle to inherit. Call super.init to initialize the base class.

3

Create subclass Bicycle inheriting from Vehicle

Create a class called Bicycle that inherits from Vehicle. Add a property hasBasket of type Bool. Create an initializer that takes speed, capacity, and hasBasket and calls the superclass initializer for speed and capacity.

Swift

class Vehicle {
    var speed: Int
    var capacity: Int
    
    init(speed: Int, capacity: Int) {
        self.speed = speed
        self.capacity = capacity
    }
}

class Car: Vehicle {
    var brand: String
    
    init(speed: Int, capacity: Int, brand: String) {
        self.brand = brand
        super.init(speed: speed, capacity: capacity)
    }
}

// Your code here

Need a hint?

Similar to Car, inherit from Vehicle and call super.init.

4

Create instances and print details

Create an instance of Car named myCar with speed 120, capacity 5, and brand "Toyota". Create an instance of Bicycle named myBike with speed 25, capacity 1, and hasBasket true. Print the details of both using print statements.

Swift

class Vehicle {
    var speed: Int
    var capacity: Int
    
    init(speed: Int, capacity: Int) {
        self.speed = speed
        self.capacity = capacity
    }
}

class Car: Vehicle {
    var brand: String
    
    init(speed: Int, capacity: Int, brand: String) {
        self.brand = brand
        super.init(speed: speed, capacity: capacity)
    }
}

class Bicycle: Vehicle {
    var hasBasket: Bool
    
    init(speed: Int, capacity: Int, hasBasket: Bool) {
        self.hasBasket = hasBasket
        super.init(speed: speed, capacity: capacity)
    }
}

// Your code here

Need a hint?

Create instances with the init method and use print with string interpolation to show properties.