DataMapper ManyToMany Update

model.rb

class Device
  include DataMapper::Resource
  
  property :id,     Serial
  property :udid,   String,   :required => true
  
  has n, :apps, :through => Resource
end

class App
  include DataMapper::Resource
  
  property :id,         Serial
  property :bundle_id,  String,   :required => true
  
  has n, :devices, :through => Resource
end

update.rb

bundle_id = app_data['bundle_id']
udids = app_data['udids']
  
result = ""

app = App.first_or_create(:bundle_id => bundle_id)
app.devices.delete_if { |device| !udids.index(device.udid) }
  
udids.each do |udid|
  found_device = false
  
  app.devices.each do |device|
    if device.udid == udid then
      found_device = true
      break
    end
  end
    
  if !found_device then
    result += "Add device '#{udid}'\n"
    device = Device.first_or_create(:udid => udid)
    device.apps << app
    device.save!
  end
end
  
app.save!