Include for instance methods in Ruby - Step-by-Step Execution

Concept Flow - Include for instance methods

Define Module with Instance Methods

↓

Define Class

↓

Include Module in Class

↓

Create Object of Class

↓

Call Included Instance Method on Object

↓

Method Executes from Module

This flow shows how a module with instance methods is included in a class, then called on an object of that class.

Execution Sample

Ruby

module Greetings
  def hello
    "Hello from module!"
  end
end

class Person
  include Greetings
end

p = Person.new
puts p.hello

This code defines a module with an instance method, includes it in a class, creates an object, and calls the method.

Execution Table

Step	Action	Evaluation	Result
1	Define module Greetings with method hello	Module created	Module Greetings with instance method hello defined
2	Define class Person	Class created	Class Person defined
3	Include Greetings module in Person	Module included	Person now has instance method hello from Greetings
4	Create object p = Person.new	Object created	p is a Person object
5	Call p.hello	Method lookup finds hello in Greetings	"Hello from module!" printed
6	End of program	No more code	Execution stops

💡 Program ends after printing the string from the included instance method

Variable Tracker

Variable	Start	After Step 4	After Step 5	Final
p	undefined	Person object created	Person object unchanged	Person object unchanged

Key Moments - 2 Insights

Why can we call p.hello even though hello is not defined in Person class?

Because the module Greetings was included in Person (see execution_table step 3), its instance methods become available to Person objects.

Is the method hello a class method or instance method of Person?

It is an instance method, because modules included with include add instance methods to the class (see execution_table step 3 and 5).

Visual Quiz - 3 Questions

Look at the execution_table at step 5, what does p.hello return?

A Error: method not found

B "Hello from module!"

C "Hello from Person!"

D nil

💡 Hint

Check the Result column at step 5 in execution_table

At which step is the module included into the class?

A Step 3

B Step 4

C Step 1

D Step 5

💡 Hint

Look at the Action column in execution_table for the inclusion action

If we remove 'include Greetings' from Person, what happens when calling p.hello?

A It prints "Hello from module!"

B It prints nil

C It raises a NoMethodError

D It calls a different method

💡 Hint

Without inclusion, the method hello is not found on Person instances (see execution_table step 3 and 5)

Concept Snapshot

module ModuleName
  def instance_method
    # code
  end
end

class ClassName
  include ModuleName  # adds instance methods
end

obj = ClassName.new
obj.instance_method  # calls method from module

Full Transcript

This example shows how to use 'include' in Ruby to add instance methods from a module to a class. First, a module named Greetings is defined with an instance method hello. Then, a class Person is defined and includes the Greetings module. This means Person objects can call hello even though it is not defined directly in Person. When we create a Person object p and call p.hello, Ruby finds the method in the included module and runs it, printing "Hello from module!". The execution table traces each step: defining the module, defining the class, including the module, creating the object, and calling the method. The variable tracker shows the object p being created and used. Key moments clarify why the method is available and that it is an instance method. The quiz questions check understanding of method lookup, inclusion step, and what happens if inclusion is removed.