Subclass with < operator in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the < operator mean when used between two classes in Ruby?

The < operator checks if the left class is a subclass of the right class. It returns true if the left class inherits from the right class, otherwise nil.

beginner

How can you check if class B is a subclass of class A in Ruby?

You can write B < A. If B inherits from A, this expression returns true.

beginner

Given <br><code>class Animal; end<br>class Dog &lt; Animal; end</code><br>What is the result of <code>Dog &lt; Animal</code>?

It returns true because Dog is a subclass of Animal.

beginner

What will Animal < Dog return given the previous classes?

It returns nil because Animal is not a subclass of Dog; it is the other way around.

intermediate

Can the < operator be used to check subclass relationships between unrelated classes?

No. If the classes are unrelated, the < operator returns nil, meaning no subclass relationship exists.

What does Child < Parent return if Child inherits from Parent?

A Raises an error

B false

C nil

D true

If Child inherits from Parent, Child < Parent returns true.

What does Parent < Child return if Child inherits from Parent?

A true

B nil

C false

D Raises an error

Parent is not a subclass of Child, so Parent < Child returns nil.

What is the result of String < Numeric in Ruby?

A nil

B true

C false

D Raises an error

String and Numeric are unrelated classes, so the < operator returns nil.

Which operator checks subclass relationships between classes in Ruby?

A ==

B &gt;

C &lt;

D !=

The < operator checks if one class is a subclass of another.

If class Cat < Animal; end, what does Cat < Animal return?

A true

B Raises an error

C nil

D false

Cat inherits from Animal, so Cat < Animal returns true.

Explain how the < operator works to check subclass relationships in Ruby.

Think about inheritance and how Ruby checks if one class inherits from another.

Describe what happens when you compare two unrelated classes using the < operator in Ruby.

Consider what Ruby returns when no inheritance link exists.