---------- Forwarded message ---------- From: Stanislav Muhametsin <[email protected]> Date: Sat, Oct 23, 2010 at 4:27 PM Subject: QI-272 To: Niclas Hedhman <[email protected]>
Quoting "Niclas Hedhman (JIRA)" <[email protected]>: [ > > http://issues.ops4j.org/browse/QI-272?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13609#action_13609 > ] > > Niclas Hedhman commented on QI-272: > ----------------------------------- > > I find your pattern very 'odd', and I am too tired right now to even try to > understand how you came to this modeling decision. > > If you want to limit the number of available instances, you should simply > prohibit it, either via a Constraint or by throwing an Exception in lifecycle > methods. Modifying Identity is not the way to go, IMNSHO. > Hmm, how can I prohibit it via a Constraint? IIRC they only affect parameters of methods. The pattern is to exploit the uniqueness of identity() property (since there is no way in Qi4j to express uniqueness of some property - that would have solved it too) in order to ensure that certain other properties are unique for this entity type. Other way is, inside create(), get all entities of current entity type (via query - this adds more load as querying service is required), and ensure that none of them has certain values in certain properties. Quite inefficient and cumbersome way to do it. Via modifying identity directly, you don't need query service and you don't need querying, you simply make it unique using the natural constraint for entites - that each entity must have unique identity. Maybe this is time to introduce @Unique annotation for properties? That would be maybe the best way to handle this. Something like @Unique(Scope.ENTITY_TYPE) (as opposed to, say, Scope.ROLE, which means that all entites, no matter what type, must have unique property). However, this would still need querying-service. -- Niclas Hedhman, Software Developer http://www.qi4j.org - New Energy for Java I live here; http://tinyurl.com/2qq9er I work here; http://tinyurl.com/2ymelc I relax here; http://tinyurl.com/2cgsug _______________________________________________ qi4j-dev mailing list [email protected] http://lists.ops4j.org/mailman/listinfo/qi4j-dev
