From: Christoph Schiessl <c.schiessl@...>
Date: 2008-05-17T01:54:36+09:00
Subject: Ruby classes and << Syntax

I have written a simple snippet of code and would appreciate any help  
with understanding what's really going on.


### Creating Basic Class
class Person # Same as: class Person < Object
   attr_accessor :firstname
   attr_accessor :lastname

   def initialize(firstname, lastname)
     @firstname, @lastname = firstname, lastname
   end

   def fullname
     @firstname + ' ' + @lastname
   end
end

### Create two instances of class Person
john = Person.new('John', 'Doe')
john.firstname # => "John"
john.lastname # => "Doe"
john.to_s # => "#<Person:0x356678>"

jack = Person.new('Jack', 'Stone')
jack.firstname # => "Jack"
jack.lastname # => "Stone"
jack.to_s # => "#<Person:0x3512f4>"

class Person
   def to_s
     'Person: ' + fullname
   end
end

john.to_s # => "Person: John Doe"
jack.to_s # => "Person: Jack Stone"
### Everything as expected until here...

### Now the interesing part:
class <<Person
   def birthday
     '2008-05-16'
   end
end

### NOT EXPECTED:
john.birthday # => NoMethodError: undefined method `birthday' for  
#<Person ...>
jack.birthday # => NoMethodError: undefined method `birthday' for  
#<Person ...>

frank = Person.new('Frank', 'New') # => Try with new instance
frank.birthday # => NoMethodError: undefined method `birthday' for  
#<Person ...>

### So basically my question is: What does the 'class <<Person'  
Statement really do?


Thank you very much!
Christoph Schiessl