Polymorphism through interfaces in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is polymorphism in TypeScript?

Polymorphism means one interface can represent different types of objects. It lets you use the same method or property name for different behaviors.

beginner

How do interfaces help achieve polymorphism in TypeScript?

Interfaces define a contract with methods or properties. Different classes can implement the same interface but behave differently, enabling polymorphism.

beginner

Example: What does this interface represent?

interface Animal { speak(): void; }

It represents any animal that can speak. Different animals can implement speak() in their own way.

intermediate

What happens when you call a method on an interface type variable?

The actual method of the object assigned to that variable runs. This is polymorphism: same call, different results.

beginner

Why is polymorphism useful in programming?

It lets you write flexible and reusable code. You can work with different objects through the same interface without knowing their exact types.

What does polymorphism allow you to do with interfaces in TypeScript?

A Create only one class from an interface

B Use the same interface for different classes with different behaviors

C Prevent classes from sharing methods

D Force all classes to have the same method implementation

Polymorphism lets different classes implement the same interface but behave differently.

Which keyword is used to make a class follow an interface in TypeScript?

A inherits

B extends

C implements

D uses

The 'implements' keyword tells TypeScript that a class follows an interface.

If two classes implement the same interface, what can you do with their objects?

A Use them interchangeably where the interface type is expected

B Only use one class at a time

C Convert one class into the other automatically

D They cannot be used together

Objects of classes implementing the same interface can be used interchangeably where that interface is expected.

What will happen if a class does not implement all methods of an interface?

A TypeScript will show an error

B The class will work fine

C The interface will change automatically

D The missing methods will be ignored

TypeScript requires all interface methods to be implemented, otherwise it shows an error.

Which of these is an example of polymorphism through interfaces?

A Writing functions without parameters

B One class inherits from another without interfaces

C Using variables without types

D Different classes implement the same interface method differently

Polymorphism means different classes implement the same interface method in their own way.

Explain how polymorphism works with interfaces in TypeScript.

Think about how one interface can represent many types.

Describe a real-life example that shows polymorphism through interfaces.

Imagine animals making sounds differently but all can speak.