On Oct 3, 2009, at 7:53 AM, Tomasz Jezierski - Tefnet wrote: >> >> if it were me, I'd just constrain access to a set of methods, such >> as: >> >> def set_col_attr(*values) > > We don't like polluting our namespace with useless get/set_col_attr > etc...
its useful depending on your use case. I have a model here which wants to receive a whole list of items at once, and its an explicit method - since thats the one way to get items into that particular collection. If I tried to instrument behind the scenes with event handlers and whatnot and attempted to flatten foo.colllection.append() and foo.collection = bar into the same system it would be a huge mess - its the definition of explciit is better than implicit. But that's my case, not yours. In this case I went back to the original email here and looked at what you're trying to accomplish. It seems like you are just trying to create an immutable collection. > > with descriptors it will be a problem with .append .remove methods > (afaik descriptor will give us only set/get/del) so as I said you'd want to implement events for the collection as well. > >> As for events on the collection itself you can still use >> attributeextension or alternatively a custom collection class. >> > We wanted to create custom event for our attributeextension but we > don't > know how to pass our impl_class to > attributes.register_attribute_impl so > that we could use our extended CollectionAttributeImpl (with modified > _set_iterable). > > Could you suggest the best way to pass our CollectionAttributeImpl to > register_attribute_impl or maybe you can modify SQLA and allow to pass > impl_class like it is done right now with collection_class. none of that should be needed - in this case, you're just trying to build an immutable collection, so collection_class is the most appropriate way to acheive this. See the docs at http://www.sqlalchemy.org/docs/05/mappers.html#custom-collection-implementations . You can elect a private method to be the @collection.appender that the ORM will use when populating the collection from the database. All pubilc mutator methods will raise an immutable exception. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
