eZ Unique Datatypes for avoiding doubles (and forcing uniqueness ;)

This is a collection of common datatypes whose validation has been extended so to verify their uniqueness within given content object attribute. Otherwise, these datatypes behave exactly as their prototypes.

Currently there are two datatypes provided:
- Unique string (based on Text line system datatype),
- Unique URL (based on URL system datatype).

Use these if you want to make sure that a given attribute of a given class never accepts/stores two identical values.

Note: uniqueness is validated globally, which means it will not skip content objects that are drafts, in trash, or unpublished versions! However, multiple versions of the same content object may store the same value (in fact, it would not work otherwise).

Note: uniqueness is validated within the same attribute only, which means that if you use the datatype in two different classes, it will become two independent attributes resulting in two independent uniqueness sets! This may be changed/enhanced in the future.

You can download it form:
http://ez.no/developer/contribs/datatypes/ez_unique_datatypes