Class Inheritance Explained in Swift

In computer programming, the purpose of the superclass and subclass is to enable related classes to share functionalities.

Here’s an example!

class Dog {
    
    var numberOfLegs = 4
    
    func walk() {
        print("I walk with \(numberOfLegs) legs")
    }
}

class Poodle: Dog {}

var myPoodle = Poodle()

myPoodle.walk() // I walk with 4 legs        

In this code, the Dog class has a numberOfLegs property with a value of 4 and a method named walk( ) that prints the number of legs the Dog walks with.

Then the Poodle class is created and it inherits from the Dog class. The syntax for when a class inherits from another is to follow the name of the subclass with a colon and then the superclass's name before the opening curly brace.

Next, the Poodle class is instantiated and the result is assigned to the variable named myPoodle.

Lastly, the walk( ) method is called on myPoodle and the output is the text: “I walk with 4 legs.”

Even though the Poodle class doesn’t define any methods or properties, it can access the numberOfLegs property and call the walk( ) method.

This is the beauty of class inheritance!

Note: To prevent a class from being subclassed, precede the name of the class with the final keyword.