动态定义class，连接database, 打印ddl

define_class_dynamiclly.rb

require 'rubygems' 
require 'active_record'

ActiveRecord::Base.establish_connection(
  :adapter => "mysql",
  :host => "localhost",
  :database => "myapp",
  :username => "root",
  :password => "root",
  :encoding => "utf8")

classes = %w(Place Activity)

classes.each do |name|
  Object.const_set name, Class.new(ActiveRecord::Base)
end

def get_ddl(model)
  model.columns_hash.each do |column| 
    puts "# #{column.first}---#{column.last.sql_type}---#{model.first.attributes[column.first]}" 
  end
end

get_ddl(Place)
get_ddl(Activity)