Method overriding in Ruby - Step-by-Step Execution

Concept Flow - Method overriding

Define Parent Class with method

↓

Define Child Class overriding method

↓

Create Child object

↓

Call method on Child object

↓

Child's method runs, not Parent's

↓

End

The child class replaces the parent's method with its own version when called on a child object.

Execution Sample

Ruby

class Parent
  def greet
    puts "Hello from Parent"
  end
end

class Child < Parent
  def greet
    puts "Hello from Child"
  end
end

child = Child.new
child.greet

This code shows a child class overriding a method from its parent class and calling the new method.

Execution Table

Step	Action	Evaluation	Output
1	Define Parent class with greet method	Parent#greet defined
2	Define Child class inheriting Parent and override greet	Child#greet defined
3	Create Child object	child is instance of Child
4	Call greet on child	Calls Child#greet (overrides Parent#greet)	Hello from Child
5	End of execution	No more code to run

💡 Program ends after calling overridden method on child object

Variable Tracker

Variable	Start	After Step 3	Final
child	undefined	Child instance created	Child instance

Key Moments - 2 Insights

Why does calling greet on child run Child's method, not Parent's?

Because the child class defines its own greet method, it overrides the parent's version. See execution_table step 4 where Child#greet is called.

What if Child did not define greet method?

Then calling greet on child would run Parent's greet method, since child inherits it. This is shown by the absence of Child#greet in step 2.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, which method is called when child.greet runs?

A Both Parent#greet and Child#greet

B Parent#greet

C Child#greet

D No method is called

💡 Hint

Check the 'Evaluation' column at step 4 in execution_table

At which step is the child object created?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look at the 'Action' column for object creation in execution_table

If Child did not override greet, what would be the output at step 4?

A "Hello from Child"

B "Hello from Parent"

C No output

D Error

💡 Hint

Refer to key_moments about what happens if Child does not define greet

Concept Snapshot

Method overriding lets a child class replace a parent's method.
Define method in parent class.
Define same method name in child class.
Calling method on child runs child's version.
If child lacks method, parent's runs.
Used for customizing behavior in subclasses.

Full Transcript

This example shows method overriding in Ruby. First, a Parent class defines a greet method that prints a message. Then, a Child class inherits Parent and defines its own greet method, replacing the parent's. When we create a Child object and call greet on it, Ruby runs the Child's greet method, not the Parent's. This is method overriding: the child class changes the behavior of a method inherited from the parent. If the child did not define greet, calling greet on the child would run the parent's method instead. This lets subclasses customize or replace behavior from their parent classes.