On Wednesday 20 August 2008 08:34:48 Felix Schwarz wrote:
> Matt Wilson schrieb:
> > On Aug 19, 9:34 pm, Jorge Godoy <[EMAIL PROTECTED]> wrote:
> >> 2. You want to receive any user_id and make it an integer, but
> >> want to raise an exception if it isn't in the database?
>
> (...)
>
> > Yeah, I figured that's *how* I could do it. I'm curious about if I
> > *should* do it this way. Is there some subtle danger in this
> > approach?
>
> I do something similar which does work really well for me: I have validator
> which transforms a given id into the appropriate model object (so I have a
> specific validator for every model object [1]) and that does work really
> well.
>
> Say the user want to view an invoice. The controller function just gets the
> invoice id but inside the function I can just work on the invoice and don't
> have to care about looking in the db, handling errors (not found, no db
> connection) etc.
>
> So if you try to validate ids, then use the validator to transform these
> ids into model objects. Else you gain next to nothing because the id could
> be deleted in the db by the time your code enters your controller function.
It gets even easier:
class ModelValidator(Int):
messages = {
'unknown_id': _("No %(model_class)r with id %(id)i")
}
def __init__(self, model_class, *args, **kwargs):
self.model_class = model_class
Int.__init__(self, *args, **kwargs)
def _to_python(self, value, state):
id_ = Int._to_python(self, value, state)
obj = self.model_class.get(id_)
if obj is None and self.not_empty:
msg = self.message(
'unknown_id',
state,
model_class=self.model_class,
id=id_
)
raise Invalid(msg, value, state)
return obj
def _from_python(self, value, state):
if value is not None:
return str(value.id)
return ""
it subclasses the Int-validator (because we want its behavior first), and then
tries to resolve for a passed model-object.
All you do is
ModelValidator(ModelClass)
Not even 2 or three lines :)
Diez
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