Inherited hook in Ruby - Step-by-Step Execution

Concept Flow - Inherited hook

Define Base Class with inherited hook

↓

Create Subclass of Base

↓

Ruby calls inherited hook

↓

Execute inherited method code

↓

Subclass modified or logged

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Subclass ready with inherited behavior

When a subclass is created, Ruby automatically calls the inherited hook method in the parent class, allowing custom code to run at that moment.

Execution Sample

Ruby

class Base
  def self.inherited(subclass)
    puts "Inherited by #{subclass}"
  end
end

class Child < Base; end

Defines a base class with an inherited hook that prints a message when a subclass is created.

Execution Table

Step	Action	Evaluation	Output
1	Define Base class with inherited method	Base class created
2	Define inherited hook method	Method stored in Base
3	Define Child subclass < Base	Ruby calls Base.inherited(Child)	Inherited by Child
4	Child class created	Child class ready

💡 Subclass Child created, inherited hook executed once

Variable Tracker

Variable	Start	After Step 3	Final
Base	Class defined	Class defined	Class defined
Child	Not defined	Defined as subclass of Base	Defined as subclass of Base

Key Moments - 2 Insights

Why does the inherited method run when I define a subclass?

Ruby automatically calls the inherited method on the parent class when a subclass is created, as shown in execution_table step 3.

Can I modify the subclass inside the inherited method?

Yes, the inherited method receives the subclass as an argument, so you can add methods or variables to it during execution (see step 3 output).

Visual Quiz - 3 Questions

Look at the execution_table, what is printed when the Child class is defined?

A No output

B "Child inherits Base"

C "Inherited by Child"

D "Base inherited by Child"

💡 Hint

Check execution_table row 3 under Output column

At which step does Ruby call the inherited hook?

A Step 2

B Step 3

C Step 1

D Step 4

💡 Hint

Look at execution_table Step column and Action describing inherited call

If you add code inside inherited to add a method to subclass, when will that method be available?

A Right after subclass is created

B Before subclass is defined

C Only after subclass is instantiated

D Never

💡 Hint

Inherited hook runs during subclass creation (see execution_table step 3)

Concept Snapshot

Inherited hook in Ruby:
- Define self.inherited(subclass) in parent class
- Runs automatically when subclass is created
- Receives subclass as argument
- Use to modify or track subclasses
- Useful for metaprogramming and callbacks

Full Transcript

This example shows how Ruby's inherited hook works. When the Base class defines self.inherited, Ruby calls this method automatically whenever a new subclass is created. In the example, when Child < Base is defined, Ruby calls Base.inherited(Child), which prints "Inherited by Child". This lets you run code right when subclasses appear, such as adding methods or logging. The execution table traces each step: defining Base, defining the inherited method, creating Child which triggers the hook, and finishing subclass creation. Variables track class definitions before and after subclassing. Common confusions include why the inherited method runs automatically and how you can modify the subclass inside it. The quiz checks understanding of when the hook runs and what output it produces. The snapshot summarizes the key points for quick recall.