Hi,

I've come across a problem with regards to a certain design pattern.

I have a User object and a PageSet object. A PageSet object has a list of User objects associated with it, but as part of that list, the User has a Color property (ie the Color property only exists for the PageSet User combination)

Could someone offer any advice on how this should be designed?

Would i need a PageSetUser object that has a PageSet, User and Color property, or would i subclass user somehow?

I've had this problem before, but never know how to resolve it.

Any help aprechiated.

Many thanks

Matt

You could probably use a <map> in the PageSet and map the User to its color. Or use a PageSetUser object, mapping as a <composite-element> of a list. Subclassing is definitely not the answer.

The PageSetUser was the only way i knew to do it myself, but it never seems right to me for some reason.

Thanks for the info on <composite-element>, i'm looking into it now.

Many thanks

Matt

We have this kind of situation all the time, and we explicit association entities (like the PageSetUser example) across the board for them. They are then mapped as one-to-manys. It can be a little cumbersome (e.g. you end up with PageSet.PageSetUser.User to get at the user) and might seem unnecessary until you realize that almost any kind of association has properties that only apply to the association and not to either entity. A classic example is the role a person plays in a project or department. that role belongs to the association between the person and the project or department, and not to the person itself. Also, it's not uncommon to want to know the date when the the association was established, or if the association is "active", etc.