Inheritance for reference types only

In object-oriented programming, inheritance refers to one class (known as a sub or child class) being derived from another class (known as a super or parent class). The subclass will inherit methods, properties, and other characteristics from the superclass. With inheritance, we can also create a class hierarchy where we can have multiple layers of inheritance.

Let's look at how we could create a class hierarchy with classes in Swift. We will start off by creating a base class named Animal:

class Animal { 
    var numberOfLegs = 0  
    func sleeps() { 
       print("zzzzz") 
    } 
    func walking() { 
       print("Walking  on \(numberOfLegs) legs") 
    } 
    func speaking() { 
       print("No sound") 
    } 
} 
 

In the Animal class, we defined one property (numberOfLegs) and three methods (sleeps(...