Subclass with < operator in Ruby

Introduction

The < operator helps you check if one class is a child (subclass) of another class. It shows if one class inherits from another.

When you want to see if a class is based on another class.

When you need to organize classes in a family tree and check relationships.

When you want to run code only if a class is a subclass of another.

When debugging to understand class inheritance.

When designing flexible code that works differently for subclasses.

Syntax

Ruby

ChildClass < ParentClass

Returns true if ChildClass inherits from ParentClass.

Returns nil if there is no inheritance relationship.

Examples

Dog is a subclass of Animal, so Dog < Animal is true. Animal is not a subclass of Dog, so Animal < Dog is nil.

Ruby

class Animal; end
class Dog < Animal; end

puts Dog < Animal  # true
puts Animal < Dog  # nil

Car inherits from Vehicle, so Car < Vehicle is true. Bike does not inherit from Vehicle, so Bike < Vehicle is nil.

Ruby

class Vehicle; end
class Car < Vehicle; end
class Bike; end

puts Car < Vehicle  # true
puts Bike < Vehicle # nil

Sample Program

This program checks if Apple and Orange are subclasses of Fruit, and if Car is a subclass of Fruit.

Ruby

class Fruit; end
class Apple < Fruit; end
class Orange < Fruit; end
class Car; end

puts Apple < Fruit
puts Orange < Fruit
puts Car < Fruit

Important Notes

The < operator works only with classes and modules in Ruby.

If you use it with unrelated classes, it returns nil.

It helps understand inheritance without creating objects.

Summary

The < operator checks if one class inherits from another.

It returns true for subclasses and nil otherwise.

Use it to understand or control class relationships.