Thank you so much! Man my wheels were spinning! Your answer, plus the section of the docs on Mutability Tracking, made all the lights go on! I needed both. The Custom Type section does have a note on mutability, but it's kind of hidden "under" the last of 3 recipes, the "Marshal JSON strings". If you want me to put in a PR to "move" that paragraph up, before the recipes, I'll gladly do so to help the next person. (Or, maybe it's in the appropriate spot, cause not many people create custom mutable versions of immutable types?).
Thanks again! On Tuesday, 31 March 2015 10:24:54 UTC-4, Michael Bayer wrote: > > > > Jeffrey McLarty <jeffrey...@gmail.com <javascript:>> wrote: > > > Hello, > > > > First - amazing work on SQLAlchemy, what an amazing body of work. > > > > Second, my question. > > > > I'm attempting to convert a pure-python object, into a custom type for > column definition. My question is, do I need to keep my original > MyObj(object) and use it inside the process_bind_param/process_result_value > of MyObjType(TypeDecorator), or should I be able to get this to work with > just one class? > > if you want to serialize your object in some special way to fit it into a > column, a TypeDecorator is the most straightforward way to go. There’s no > magic method that SQLAlchemy calls on your object; only if you used > PickleType you could define a serializer. > > > > More: > > > > I'm confused about the *arg and **kw passed to typeobj, in the > to_instance() function, from type_api.py...when those might conflict with > my object constructor's parameters. > > those are arguments referring to the type object, not your actual object. > They are two separate things. > > > > > ...if anybody wants to have a look at my code, it is on github, > organized into a PR, https://github.com/Equitable/trump/pull/15 with > links to the files and line numbers. > > right…that’s not right. You need two different objects. One would be > BitFlag, with all of the special logic you have here, and the other would > be > BitFlagType. BitFlagType wouldn’t really need anything in its constructor, > just the process_bind_param / process_result_value methods. > > However! This specific case has a special bonus feature. Your BitFlag > implementation could just as well be a subclass of int (e.g. class > BitFlag(int)) and you’d get the process_bind_param part for free in that > case. Though you’d still probably want process_result_value so that when > you > load from the database, you get BitFlag objects back and not just plain > ints. > > Either way the TD will be along these lines: > > class BitFlagType(TypeDecorator): > > impl = Integer > > def process_bind_param(self, value, dialect): > if value is not None: > value = value.int_field > > return value > > def process_result_value(self, value, dialect): > if value is not None: > value = BitFlag(value) > return value > > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.
