Re: Twisty Little Passages... widgets, fields, forms

On Jun 1, 1:24 am, Michael Davis <davis.j.mich...@gmail.com> wrote:
> I'm trying to implement a simple grade book application using a
> modelformset where the students' names are READONLY and the grades are
> the only thing the teacher can edit. I've been looking for sample code
> to implement the readonly portion and one fellow (on another site)
> suggests I use his, but he never posts sample usage code along with
> it.
>
> He suggests I use a custom widget:
> class ReadOnlyWidget(forms.Widget):
>     def __init__(self, original_value, display_value=None):
>         self.original_value = original_value
>         if display_value:
>             self.display_value = display_value
>         super(ReadOnlyWidget, self).__init__()
>     def _has_changed(self, initial, data):
>         return False
>     def render(self, name, value, attrs=None):
>         if self.display_value is not None:
>             return unicode(self.display_value)
>         return unicode(self.original_value)
>     def value_from_datadict(self, data, files, name):
>         return self.original_value
>
> But I can't figure out how to set the original_value in my
> application.
> The "obvious" choice like:
> class GradeForm(ModelForm):
>     student = forms.CharField(max_length=50,
> widget=ReadOnlyWidget(instance))
> doesn't work as I'm fairly sure instance isn't set here or if it is
> how I can invoke it so it does the right thing in a modelformset.
>
> The less obvious choice of setting it from within the form's __init__
> function is currently beyond my ability as I do not understand the
> code flow through here and am not sure how to instantiate the widget
> from within the form's __init__ function.
>
> Can someone point me to a good source of documentation at this level
> of detail?

I know this is not answering your question directly, so please just
sigh and ignore it if not relevant...

If this is a simple application", as you mention above, maybe consider
(or reconsider) using the Admin application, which has built-in
support for readonly fields.

http://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.readonly_fields

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