Am 25.06.2012 16:56, schrieb Alessandro Molina:
By the way, is anybody working on a TW2 version of the forms tutorial
(http://turbogears.org/2.1/docs/main/ToscaWidgets/forms.html) already? If
not, I'm volunteering to do it.
Should have been already updated in new doc
(http://turbogears-dev.readthedocs.org/en/latest/main/TwForms.html)
if you find anything wrong feel free to change it, it has been created
on TW2.0 and TW2.1 release might have changed something.
Oh, great. Hadnt' seen this yet. But the new tutorial does not cover as
much ground as the old one, which explained various ways of displaying
help texts, storing values and reading options with SQLAlchemy. The old
one also had screen shots which is always important for newbies: You
want to see how things should look like if you do everything right.
Yep, the current TG2.2 form documentation already has examples that
pass around the class itself.
In TW2 you are expected to always use the class of the widgets
wherever you used a widget instance before.
The class itself has the display staticmethod and so on.
We really need to elaborate on that in the docs. The TW2 tutorial
recommends using an instance created with req(). The idea of TW2 is
actually that you can change widget instances per request. If you pass
only classes, you can't do that. Furthermore, passing parameters to
widgets using child_args does not work any more in TW2, the only way to
do that is to operate on the instance.
Here is a typical use case: How would you inject an options list
dynamically in TW2? In our movie database example, assume that the
"genre" options list depends on the user/request. As far as I
understand, you must do it like this in TW2:
@expose('.templates.new_form')
def new(self, **kw):
form = MovieForm.req()
form.child.children.genre.options = enumerate([
'Comedy', 'Drama', 'SciFi']) # something variable
tmpl_context.form = form
return dict(modelname='Movie', value=kw)
But then you run into the validation problem again: When the form is
re-displayed as result of an error, the error messages won't show up.
One idea to solve this would be:
if tmpl_context.form_errors:
form = MovieForm
else:
form = MovieForm.req()
form.child.children.genre.options = enumerate([
'Comedy', 'Drama', 'SciFi'])
tmpl_context.form = form
Now in case of an error, the request local instance created by the
validation process will be picked up. That instance knows about the form
values and errors, but it does not know about the genre.options. So in
case of an error, the option list will not be populated-
The only proper workaround that comes to my mind is this one, which does
not look very nice and accesses TW2 internal stuff:
try:
form = tw2.core.core.request_local()['validated_widget']
except KeyError:
form = MovieForm.req()
form.child.children.genre.options = enumerate([
'Comedy', 'Drama', 'SciFi'])
tmpl_context.form = form
Do you have any better idea how to solve this use case? If not, I'll
take this problem to the TW2 mailing list.
-- Christoph
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