I'm interested in what you find. I know TypeDecorator is the right
solution, I was looking at that for this exact same situation a few weeks
ago
(
https://groups.google.com/forum/#!searchin/sqlalchemy/vanasco%7Csort:date/sqlalchemy/sQtOYxSUiqI/5ns2vWMFaGAJ
)
I have a similar situation. I wrote a generic bitwise wrapper class that I
was ashamed of, but I guess I should eventually release it. i can toss it
on github under the MIT if you'd like.
The way I have my bitwise stuff working is this:
* I create an class that inherits from my `BitwiseSet` class. That
subclass stores a mapping of the bitwise values, the parent class has
functions for common bitwise operations ( add, remove, has_any, has_all --
both by string and integer ). The parent class has an 'encode' and
'decode' function, which returns an int or list of elements (as int or
string ).
class BitwiseClassFieldA(BitwiseSet):
set_ = {
'flag_a' << 1,
'flag_b' << 2,
'flag_c' << 3,
}
* I have a property on each of my sqlalchemy objects that works something
like this...
class Foo(SqlAlchemyObject):
bitwise_field_a = sa.Column( sa.Integer, default=0 )
@property
def bitwise_manager_field_a(self):
if self._bitwise_manager_field_a is None:
self. bitwise_manager_field_a =
BitwiseClassFieldA(self.bitwise_field_a)
return self.bitwise_manager_field_a
_ bitwise_manager_field_a = None
* when i do saves , i call the manager's `encode` function
instance.bitwise_field_a = instance.bitwise_manager_field_a.encode()
anyways, when I was trying to get a TypeDecorator working, I was focused on
the Integer field having a decorator and managing my object -- not on
defining many column attributes like you are. i think that might be an
easier avenue, because you want to affect the column itself for these
comparisons.
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