DDD - Validation of unique constraint

Posted by W3Max on Stack Overflow See other posts from Stack Overflow or by W3Max
Published on 2010-04-18T02:03:14Z Indexed on 2010/04/18 2:13 UTC
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ddd

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validation

In DDD you should never let your entities enter an invalid state. That being said, how do you handle the validation of a unique constraint?

The creation of an entity is not a real problem. But let say you have an entity that must have a unique name and there is a thousand instances of this entity type - they are not in memory but stored in a database. Now let say you want to rename an instance.

You can't just use a setter... the object could enter an invalid state - you have to validate against the database.

How do you handle this scenario in a web environment?

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