I’m learning about Domain Driven Design and struggling with the question if a particular object should be handled as entity or value object.
All possible surname prefixes are kept in a database table. (The data is used in a combo box). Since there are records kept of all these prefixes, should Prefix be seen as an entity? Or is it still possible to handle it as a value object?
You already gave the answer yourself in your comment to the other question: If two Prefix objects with the same content are interchangeable, then Prefix is (probably) a value object.
Another rule of thumb is: “Domain first, infrastructure second”, i.e., don’t let infrastructure concerns (here: primary keys in database tables) influence your domain model.
I thought the difference was the linkage with the database. So an Entity object has state that maintains its place in the DB, whereas a value object simply contains the data.
Writing the object back to the DB ends up as a update call in both cases, however the entity will use the internally-held key to refer back to the DB row, whereas the value object needs to get the key from its data… not much difference in practice ultimately!
I’d prefer a value object as I’m old-fashioned that way, I’d read only what was needed and update just that data. Less data and less state is always good.
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