I’d like to start this article with a quote from Ross Tuck’s article “Persisting Value Objects in Doctrine”. He describes different ways of persisting value objects when using Doctrine ORM. At the end of the page he gives us the following option - the “nuclear” one:

[…] Doctrine is great for the vast majority of applications but if you’ve got edge cases that are making your entity code messy, don’t be afraid to toss Doctrine out. Setup an interface for your repositories and create an alternate implementation where you do the querying or mapping by hand. It might be a PITA but it might also be less frustration in the long run.

This is a question that always pops up during my workshops: when and where to determine the ID of an entity? There are different answers, no best answer. Well, there are two best answers, but they apply to two different situations.

Auto-incrementing IDs, by the database

Traditionally, all you need for an entity to have an ID is to designate one integer column in the database as the primary key, and mark it as “auto-incrementing”. So, once a new entity gets persisted as a record in the database (using your favorite ORM), it will get an ID. That is, the entity has no identity until it has been persisted. Even though this happens everywhere, and almost always; it’s a bit weird, because: