On Apr 7, 2011, at 4:36 PM, Luca Lesinigo wrote: > Hello there. I'm using SA-0.7 to develop an application that should > help me manage my company's services. > > A central concept here is the order, it could be a service (like one > year of web hosting) or a physical item (like a pc we sell). So far I > generalized them in two classes: the Order and the ServiceOrder - the > latter simply inherits the former and adds start and end dates. > > Now I need to add all various kinds of metadata to orders, for > example: > - a ServiceOrder for a domain hosting should contain the domain name > - a ServiceOrder for a maintenance service should contain the service > level for that service (say, basic or advanced) > - an Order for a PC we delivered should contain its serial number > - and so on... > > I could easily add child classes, but that would mean to keep and > maintain that code forever even after we stop using it (ie, next year > we stop doing hosting) or when it's not really useful (many things > will just have some 'metadata' in them like a serial number or similar > things). I'd also like to avoid having to add code every time we just > hit something slightly different to manage, when we just have some > additional data to keep track of. > I wonder what could be an intelligent approach to such a situation.
why not separate the product from the fact of its being ordered ? compose Order->Product instead of inherit. As far as variable attributes which you only need to retrieve, never to query on, there are many recipes for a "bag" of attributes. By far the easiest is a recipe like JSON type: http://www.sqlalchemy.org/docs/core/types.html#marshal-json-strings More broken out are key/value tables, this is more like your ordertags idea. recipes: http://www.sqlalchemy.org/docs/orm/examples.html#vertical-attribute-mapping http://www.sqlalchemy.org/trac/wiki/UsageRecipes/VersionedMap -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
