gistfile1.rb

# DM Extensions

# Use for roll your own optimistic locking, without using a dedicated lock_version column
def update_with_conditions(attributes, conditions)
  properties = attributes.inject({}) do |a, (key, value)|
    a.update(property_by_name(key) => value)
  end

  updated_count = repository.adapter.update(properties, all(conditions))

  raise StaleObjectError if updated_count != 1
end

def property_by_name(name)
  properties.detect {|x| x.name == name }
end


# Code
IndexInstrument.update_with_conditions({:name => 'NEW'},
  :id   => existing.id,
  :name => 'OLD')