gistfile1.rbx

class DataMapper::Property

  # translate the value from external source to expected object
  def typecast(value)
    value
  end

  # translate the value from the primitive to expected object
  def load(value)
    value
  end

  # translate the value from expected object to the primitive
  def dump(value)
    value
  end
end

# defaults are specified on a per-type basis as before
class DataMapper::Property::String < DataMapper::Property

  supports_options :length, :size, :default, :nullable, ...

  DEFAULT_LENGTH = 50

  # the initialize can be specific to each type.  the current
  # initialize method in DM::Property is monolithic and has logic to
  # support all of the basic types.  with this new organization the
  # logic can be separated out on a per-subclass basis.
  def initialize(options)
    super
    @length = options.fetch(:length, DEFAULT_LENGTH)
  end
end

# you can specify the "adapter" specific configuration within
# the adapters themselves
class DataMapper::Adapters::DataObjectsAdapter
  DataMapper::Property::String.adapter(self) do
    native_type 'VARCHAR'
  end
end

# or within the types if you wish
class DataMapper::Property::UUID < DataMapper::Property::String
  def typecast(value)
    value.kind_of?(::UUID) ? value : load(value)
  end

  def load(value)
    ::UUID.parse(value) unless value.nil?
  end

  def dump(value)
    value.to_s unless value.nil?
  end

  # would use VARCHAR for all DOA subclasses because it's
  # defined for the parent DM::Property::String class, but for
  # PG it would use the native UUID type
  adapter(PostgresAdapter) do
    native_type 'UUID'
  end
end