Ruby - Basic Inheritance

This post talks about how to implement basic inheritance in Ruby using a simple example. I’ll throw in some comparisons with Java.

Our Parent and Child Classes

The simplest example of Parent-child inheritance is as follows.

class Parent
  # methods and other codes here
end

class Child < Parent
  # methods and other codes here
end

class Parent

# methods and other codes here

end

class Child < Parent

# methods and other codes here

end

In Java, this is equivalent to

public class Parent {} 
public class Child extends Parent {}

1 2	public class Parent {} public class Child extends Parent {}

Overriding methods

Let’s modify the original Ruby codes so that the Parent class has a method

class Parent
  def walk
    puts "In parent..."
  end
end

class Child < Parent
  # No methods defined or re-defined here
end

# Let’s create an instance of Child 
# and invoke the inherited walk method 

my_child = Child.new
my_child.walk()

class Parent

def walk

puts "In parent..."

end

class Child < Parent

# No methods defined or re-defined here

end

# Let’s create an instance of Child

# and invoke the inherited walk method

my_child = Child.new

my_child.walk()

These codes will output:

In parent...

1	In parent...

Now if we re-define the same walk method in the Child class that displays a different string

class Parent
  def walk
    puts "In parent..."
  end
end

class Child < Parent
  def walk
    puts "In Child..."
  end
end

# Let’s create an instance of Child 
# and invoke the inherited walk method 

my_child = Child.new
my_child.walk()