Can't define accessors for serialized attributes

Hi there. With ordinary attributes, I can write an accessor like this:

class Foo < ActiveRecord::Base
  # column :foo, :integer
  def foo
    read_attribute(:foo) || write_attribute(:foo, 123)
  end
end

and I get, effectively, a default value for the column. There are lots of other uses for writing your own attribute accessors.

This doesn't work with serialized attributes:

class Foo < ActiveRecord::Base
  # column :bar, :text
  serialize :bar, Hash

  def bar
    read_attribute(:bar) || write_attribute(:bar, Hash.new)
  end
end

f = Foo.new
f.bar # nil

AR is overriding my accessor with its own. Consequently, everywhere I want to use the "bar" attribute, I have to say something like "(f.bar ||= Hash.new)[:a] = 1".