oop - What is the difference between polymorphism and duck typing?

Question

I'm a little confused with the two terms, here's what I know:

Polymorphism is the ability of object of different types to be handled by a common interface. While duck typing, is a kind of dynamic typing that allows objects of different types to respond to the same methods.

From what I understand, polymorphism is more about creating an interface that can be shared across different classes. And duck typing is about loose typing that will allow methods to be called as long as it is found on the receiver of the message.

Is this correct? I'm pretty confused on the two, they seem related but I do not know what their relationship is. Thanks a lot in advance!

Answer 1

Polymorphism (in the context of object-oriented programming) means a subclass can override a method of the base class. This means a method of a class can do different things in subclasses. For example: a class Animal can have a method talk() and the subclasses Dog and Cat of Animal can let the method talk() make different sounds.

Duck typing means code will simply accept any object that has a particular method. Let's say we have the following code: animal.quack(). If the given object animal has the method we want to call then we're good (no additional type requirements needed). It does not matter whether animal is actually a Duck or a different animal which also happens to quack. That's why it is called duck typing: if it looks like a duck (e.g., it has a method called quack() then we can act as if that object is a duck).

So are these related? They are simply separate features that a programming language may have. There are programming languages which have polymorphism but that do not have duck typing (such as Java). There are also languages that have polymorphism and duck typing (such as Python).