gistfile1.rb

require 'rubygems'
require 'dm-core'

# DataMapper.setup(:legacy, "sqlite3:///#{Dir.pwd}/legacy.db")
# DataMapper.setup(:new, "sqlite3:///#{Dir.pwd}/new.db")
DataMapper.setup( :legacy, 
                  :adapter => "mysql", 
                  :encoding => "utf8", 
                  :database => "dm_legacy", 
                  :username => "root",
                  :host     => "localhost" )
                  
DataMapper.setup( :new,                   
                  :adapter => "mysql", 
                  :encoding => "utf8", 
                  :database => "dm_new", 
                  :username => "root",
                  :host     => "localhost" )


module DataMapper
  module Types
    class LegacyBlogId < DataMapper::Type
      primitive String
      def self.load(value, property)
        case value
        when 'en'
          1
        else
          2
        end
      end

    end
  end
end

class LegacyArticle
  include DataMapper::Resource
    storage_names[:legacy] = 'articles'
    property :id,           Serial
    property :text,         Text
    property :title,        String,   :length => 255
    property :language,     String,   :default => "en"
    property :created_on,   DateTime  
end

class NewArticle
  include DataMapper::Resource
    storage_names[:new] = 'items'
    property :id,           Serial
    property :body,         Text
    property :main_title,   String,   :length => 255
    property :blog_id,      Integer,   :default => 1
    property :created_at,   Date
    property :created_on,   DateTime
    property :author_id,    Integer,   :default => 1
  
end

class Article
  include DataMapper::Resource
    storage_names[:legacy] = 'articles'
    storage_names[:new] = 'items'
    
    property :id,           Serial
    property :body,         Text
    property :title,        String
    property :created_on,   DateTime
    property :created_at,   DateTime
    property :author_id,    Integer
    property :blog_id,      Integer
    
    repository(:legacy) do
      property :body,       Text,           :field => "text"
      property :blog_id,    LegacyBlogId,   :field => "language"
      property :created_at, DateTime,       :field => "created_on"
      # property :author_id  Skip
    end
    
    repository(:new) do
      property :title,      String,         :field => "main_title"
    end
    
    # quick hack to avoid yet another DM bug
    def to_hash
      property_hash = {}
      Article.properties.defaults.map{|property| property_hash[property.name] = self.send(property.name)}
      property_hash.except(:id)
    end
    
    # Monkey patch the copy method to work
    def self.copy(source, destination, query={})
      repository(destination) do
        repository(source).read_many(DataMapper::Query.new(repository(source), self, query)).each do |resource|
          self.create(resource.attributes.except(:id))
        end
      end
    end
    
end


# Load some data in the legacy repo
repository(:legacy) do
  LegacyArticle.auto_migrate! 
  LegacyArticle.create(:text => "this is a legacy body", :title => "this is the title", :language => "fr", :created_on => Time.now) 
  LegacyArticle.create(:text => "this is another legacy body", :title => "this is another title", :created_on => Time.now) 
  puts "legacy articles created"
end

# Load some data in the new repo
repository(:new) do 
  NewArticle.auto_migrate!
  NewArticle.create(:body => "this is a new body", :main_title => "this is the title", :blog_id => 1, :created_on => Time.now, :created_on => Time.now) 
  NewArticle.create(:body => "this is another new body", :main_title => "this is another title", :blog_id => 2, :created_on => Time.now, :created_on => Time.now) 
  puts "new articles created"
end


begin
  Article.copy(:legacy, :new)
rescue  Exception => e
  puts "Boo Model#copy didn't work!  #{e}"
else
  puts "Model#copy worked fine"
end

begin
  old_article = repository(:legacy) { Article.first }
  new_article = repository(:new) { Article.first }
  fresh_article = repository(:new) { Article.new }
  fresh_article.attributes = old_article.to_hash
  repository(:new) { fresh_article.save }
rescue Exception => e
  puts "new object with legacy attributes failed #{e}"
else
  puts fresh_article.attributes.inspect
  puts "new object with legacy attributes worked fine!"
end