datamapper/datamapper.github.com — pull request #45 by crantok (2013-12-10 15:02:23+00:00)
Title: Added note about adding properties to supplement associations

Sometimes it would be desirable to add options to associations when those options are only valid for properties. In these cases, a supplementary property must be added to support the association. This edit adds an example: Applying :unique_index to an association.