Keeping it Classy

constant_class.rb

# Foo is a constant that 
Foo = Class.new
# We can define a superclass as an argument of the Class#new method,
# but the default is Object, and we are fine with that.
#=> Foo

Foo.class_eval do
  def bar
    :baz
  end
end
#=> nil

Foo.instance_eval do
  def baz
    :bar
  end
end
#=> nil


Foo.bar
Foo.new.baz
#=> Both raise an error

Foo.baz
Foo.new.bar
#=> :bar and :baz, respectively

# This is a little different, but still somewhat familiar looking.

normal_class.rb

class Foo
  def bar
    :baz
  end

  def self.baz
    :bar
  end
end
#=> nil

foo = Foo.new
# returns a new Foo object, foo

foo.bar
#=> :baz

# This is how we normally declare our classes.
# I think that this is because this is how we teach
# other languages, so teaching Ruby this way is just easier.
# However, there are other ways we can do things.

variable_class.rb

foo = Class.new
# returns an instance of Class

foo.new
# returns an instance of the instance of Class.

foo.new.class
# returns our instance of class.

foo.class_eval do 
  def bar
    :baz
  end
end
#=> nil

foo.new.bar
#=> :baz

foo = 0

foo.new.bar
#=> raises an error, it's not a class anymore, dummy!

# Here we are just using a variable that we can overwrite to define our class