Inherited hook in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the inherited hook in Ruby?

The <code>inherited</code> hook is a special method in Ruby that is called automatically whenever a subclass is created from a class. It lets the parent class react to the creation of its child classes.

beginner

How do you define an inherited hook in a Ruby class?

You define a class method named <code>self.inherited(subclass)</code> inside the parent class. Ruby calls this method with the new subclass as the argument whenever a subclass is created.

intermediate

What can you do inside the inherited hook?

Inside the inherited hook, you can run code to customize or track subclasses. For example, you can add methods, set variables, or keep a list of all subclasses.

beginner

Example: What will this code print?<br><pre>class Parent
  def self.inherited(subclass)
    puts "New subclass: #{subclass}"
  end
end

class Child < Parent
end</pre>

It will print: <br>New subclass: Child<br>This happens because when Child inherits from Parent, the inherited hook runs and prints the message.

intermediate

Why is the inherited hook useful in Ruby?

It helps you automatically run code when new subclasses are made. This is useful for tracking subclasses, adding shared behavior, or setting up configurations without changing each subclass manually.

What argument does the inherited hook receive?

A The parent class

B The new subclass

C An instance of the subclass

D No arguments

The inherited hook receives the new subclass as its argument.

Where do you define the inherited method?

A Inside an instance method

B Inside the subclass

C Outside any class

D Inside the parent class as a class method

You define self.inherited(subclass) as a class method inside the parent class.

What happens when a subclass is created and the parent class has an inherited hook?

A The <code>inherited</code> method runs automatically

B The subclass is deleted

C Nothing special happens

D The parent class is redefined

The inherited method runs automatically when a subclass is created.

Which of these is a common use of the inherited hook?

A To track all subclasses

B To create instances

C To override instance methods

D To delete subclasses

Tracking all subclasses is a common use of the inherited hook.

Can the inherited hook modify the subclass?

A Yes, but only instance methods

B No, it only reads subclass info

C Yes, it can add methods or variables

D No, it only runs after subclass is deleted

The inherited hook can modify the subclass by adding methods or variables.

Explain what the inherited hook does in Ruby and give a simple example.

Think about what happens when you create a new subclass.

Describe a practical use case for the inherited hook in a Ruby program.

Why would you want to know when a subclass is created?