belongs_to_fail.rb

require 'rubygems'
require 'dm-core'
require 'pp'

DataMapper.setup(:default, "sqlite3::memory:")

class City
  include DataMapper::Resource

  property :id, Serial
  property :name, String, :nullable => false
end

class Person
  include DataMapper::Resource

  property :id, Serial
  property :name, String, :nullable => false

  belongs_to :birth_place, :class_name => 'City'
  belongs_to :work_place, :class_name => 'City'
end

DataMapper.auto_migrate!

pp joe = Person.create(:name => 'Joe')
pp betty = Person.create(:name => 'Betty')

pp sf = City.create(:name => "San Fran")
pp la = City.create(:name => "Los Angeles")

joe.birth_place = sf
joe.work_place = la
pp joe.save
pp joe

betty.birth_place = sf
betty.work_place = sf
pp betty.save
pp betty

# Both associations use the 'city_id' property without any change for overriding