association.rb

#!/usr/bin/env ruby                                                                                                                                                                                                                                                                    

require 'data_mapper'                                                                                                                                                                                                                                                                  
DataMapper::setup(:default, "sqlite3://#{File.expand_path('app.db')}")                                                                                                                                                                                                                 


module MyApp                                                                                                                                                                                                                                                                           
  class DB                                                                                                                                                                                                                                                                             
    class Page                                                                                                                                                                                                                                                                         
      include DataMapper::Resource                                                                                                                                                                                                                                                     
      property :id, Serial, :key => true                                                                                                                                                                                                                                               
      has n, :photos                                                                                                                                                                                                                                                                   
      has 1, :main_photo, 'Photo'                                                                                                                                                                                                                                                      
    end                                                                                                                                                                                                                                                                                
  end                                                                                                                                                                                                                                                                                  
end                                                                                                                                                                                                                                                                                    


module MyApp                                                                                                                                                                                                                                                                           
  class DB                                                                                                                                                                                                                                                                             
    class Photo                                                                                                                                                                                                                                                                        
      include DataMapper::Resource                                                                                                                                                                                                                                                     
      property :id, Serial, :key => true                                                                                                                                                                                                                                               
      belongs_to :page                                                                                                                                                                                                                                                                 
    end                                                                                                                                                                                                                                                                                
  end                                                                                                                                                                                                                                                                                  
end                                                                                                                                                                                                                                                                                    




DataMapper.finalize                                                                                                                                                                                                                                                                    
DataMapper.auto_upgrade!                                                                                                                                                                                                                                                               




puts "==> Page"                                                                                                                                                                                                                                                                        
puts page = MyApp::DB::Page.create                                                                                                                                                                                                                                                     

puts "==> Photos"                                                                                                                                                                                                                                                                      
3.times { puts MyApp::DB::Photo.create(:page => page) }                                                                                                                                                                                                                                


page = MyApp::DB::Page.get(1)                                                                                                                                                                                                                                                          
puts "==> Page Photos"                                                                                                                                                                                                                                                                 
puts page.photos                                                                                                                                                                                                                                                                       


# why does this get set?                                                                                                                                                                                                                                                               
puts "==> Page Main Photo"                                                                                                                                                                                                                                                             
puts page.main_photo                                                                                                                                                                                                                                                                   

# this fails!                                                                                                                                                                                                                                                                          
puts page.update(:main_photo => MyApp::DB::Photo.get(3))