class Blog
  @@options = { :adapter  => "mysql2" }

  def self.options
    @@options
  end

  def initialize(options = Hash.new)
    @@options = {
      :adapter  => "mysql2",
      :host     => options[:host] || "localhost",
      :username => options[:user] || "root",
      :password => options[:pass] || "",
      :database => options[:db] || "my_blog"
    }
  end
end

module Foobar
  class Post < ActiveRecord::Base
    establish_connection(Blog.options)
  end
end

Blog.new(user:"foo",pass:"bar",db:"bang")
p=Foobar::Post.all