class Object
  attr_reader :foo
  def initialize
    @foo = 'bar'
  end
end

Object.new.foo # => 'bar'
''.foo # => nil
//.foo # => nil
[].foo # => nil

I want them all to return 'bar'

Am aware that you can do this already:

class Object
  def foo
    'bar'
  end
end

But I specifically want to initialize a state variable. Also note that this doesn't work.

class String
  alias_method :old_init, :initialize
  def initialize(*args)
    super
    old_init(*args)
  end
end

class Object
  attr_reader :foo
  def initialize
    @foo = 'bar'
    super
  end
end

''.foo # => nil

Nor does this:

class String
  attr_reader :foo
  def initialize
    @foo = 'bar'
  end
end

''.instance_variables # => []

I'm beginning to think that this isn't actually possible.