gistfile1.rb

# attr_accessor is "syntatic sugar" for dynamically defining attribute
# readers and accessors. Foo and Bar are functionally equivilant.
#
# Remember @instance_variables are only visible in the scope
# of the instance. If you need to access them from outside the instance,
# they must be exposed through accessors. 

class Foo
  attr_accessor :bar
end

foo = Foo.new
foo.bar = 'Baz'
foo.bar # => 'Baz'

class Bar
  def foo=(value)
    @foo = value
  end
  
  def foo
    @foo
  end
end

bar = Bar.new
bar.foo = 'Baz'
bar.foo # => 'Baz