On Mon, 19 May 2008 09:19:26 +1000 Aristedes Maniatis <[EMAIL PROTECTED]> wrote:
> There should be something coming soon with inheritance, but there were > no plans to support persistent objects with no database backing at > all. There is going to be the opposite concept: abstract classes which > have a database table, but which can only be constructed in their > subclass. > > Tell us more about why it would be useful to have data objects which > cannot be persisted to the database. I guess my usage scenario is very specific to my environment. But let me introduce my environment and let you decide. I have written a UI renderer and data binding engine (Gozer). For that engine to work I introduced the Domain Model, Table Module and Record Set patterns and DataObjectKeys to Cayenne (at least to some extent). I did so with my own code generator which generates datarows, datarowkeys and table modules to every ObjEntity modeled with the Cayenne modeler. For the data binding I use then these table modules. Let's say I have a table with users. I can then bind that table to the UI like that: <list databinding="@user"> <list_field databinding="username" /> </list> My UI engine is interpreting the binding information so that the UI renders a list of users with the only field in the list containing the username. Which means that whenever I display data on the UI, I am using the same databinding which makes use of my datatable and datarow objects. Now to the QueryTable problem: Many applications have some form of user input where a user can enter search criteria and then use that criteria to filter a list of records or search data in the database. Since my UI engine knows how to render my table modules and datarows, I would love to use the same mechanism for query interfaces (a huge time saver). To extend my example from above: I could introduce a UserQueryTable with a field UserName. I could then define a view which binds that table. The user enters a username and when clicking on the search button I could read the content from the UserQueryTable and construct the query from the content of that table. Side effect, all my queries would be "standardised" and whenever I need to search for users in my application I can use the same interface (UserQueryTable) which is then sent to the UserQuery Business Object which handles the querying in a central location (domain model pattern). Of course I could solve that problem in creating ObjEntity which have a corresponding table in the database (which is never used). But I find this to be very ugly... Hope this explained my scenario. Cheers, Adrian
