On Monday 07 January 2008 10:10:59 Daniel Fetchinson wrote:
> I have a number of classes that subclass SQLObject as well as a mixin
> class and now would like to jsonify them:
>
> class myclass1( SQLObject, Mixin ):
> .........
> .........
>
> class myclass2( SQLObject, Mixin ):
> ..........
> ..........
>
> Since I have other classes that only subclass SQLObject I need to keep
> the jsonify_sqlobject rule too but simply using @jsonify.when(
> 'isinstance( obj, Mixin )' ) raises an AmbiguousMethod exception
> because my objects match both isinstance( obj, SQLObject ) and
> isinstance( obj, Mixin ). After looking into RuleDispatch this is to
> be expected because neither of the two conditions is more specific
> than the other so an AmbiguousMethod exception is raised. So far I
> understand the story.
>
> When is not clear is how to work around it. How would I force
> RuleDispatch to use my rule? I thought @jsonify.before( 'isinstance(
> obj, Mixin )' ) would do the trick because the 'before' method would
> come before the primary rule but it doesn't work, only the original
> jsonify_sqlobject rule is run.
Just a thought, not sure if it works:
class MyBase(SQLObject, Mixin):
pass
class myclass1(MyBase):
. ...
If that works, go for it - if not, I'd say: one rule for each of your myclass*
is ok, or do you write so many of them? You could of course use the same
inner code then, either by registering one function for several signatures or
via a delegated call.
Diez
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