A very short introduction to ruby inheritance

1. Inheritance*in*Ruby
Daniel'Berkompas

2. Two$Kinds
• Parent(Child.Inheritance
• Module.Inheritance

3. Parent'Child-Inheritance

4. Parent'Child-Inheritance
class Parent
# ... lots of stuff
end
class Child < Parent
# Child gets everything Parent has
end

5. Parent'Child-Inheritance
• Classes'can'have'only'one'Parent'(Superclass)
• There'is'no'limit'to'how'many'Children'a'Parent'can'have'
(Subclass)
class Grandparent; end
class Parent < Grandparent; end
class SiblingOne < Parent; end
class SiblingTwo < Parent; end

6. Overriding)Methods

7. Overriding)Methods
class Parent
def say_hello
@var = "Hello, World!"
end
end
class Child < Parent
end
Child.new.say_hello # => "Hello, World!"

8. Overriding)Methods
class Parent
def say_hello # Collapsed for space ...
end
class Child
def say_hello
super
@var += " Goodbye, World!"
end
end
Child.new.say_hello # => "Hello, World! Goodbye, World!"

9. Module'Inheritance

10. Module'Inheritance
module Friendliness
def say_hello
@var = "Hello, World!"
end
end
class Child
include Friendliness
end
Child.new.say_hello # => "Hello, World!"

11. Module'Inheritance
Children)will)get)their)parent's)modules,)too.
class Parent
include Friendliness
end
class Child < Parent
end
Child.new.say_hello # => "Hello, World!"

12. When%Should%I%Use%Inheritance?

13. When%You%Should%Use%Class%Inheritance
• When&you're&doing&the&same&thing&a&lot
• When&mul4ple&classes&in&your&database&"are"&the&same&kind&of&
thing&with&slight&differences
Example:)A)ship)in)the)X1Wing)Miniatures)Game)should)be)a)child)
of)a)Ship)class.

14. When%You%Should%Use%Class%Inheritance
• When&you're&doing&the&same&thing&a&lot
• When&mul4ple&classes&have&similar&traits,&but&they%aren't%the%
same%thing.
Example:)Wheat)Grinders)and)Cars)both)have)wheels)but)they)
aren't)similar)things)at)all.

15. Ques%ons