On Jul 14, 2005, at 9:04 PM, mso@oz.net wrote:

>
> Is this the right way to do it?  Should my ._parse method set the
> value to
> a tuple of subvalues, and .set_value propagate the values to the
> subwidgets?  Or should I ignore the widget value and have caller
> look at
> the subwidget values directly?  "form.get_widget('quantity')['low']"?
> I suppose I can't do "form['quantity']['low']" ?

I think that the first option you suggest, setting the value to a tuple,
or to an instance of a class you write for this particular purpose,
is a good
way to do it.  The user of the widget should not need be aware of the
particulars of the subwidgets.

>
> What if I need several range controls on the same form?  All the
> subwidgets will be in a flat namespace in the HTML.  I'm getting
> subwidget
> names like 'release$low', so I guess that's being taken care of
> automatically somehow.

Right, you would just get the _parsed value from your composite
widget as
if it were a non-composite widget.

>     def _parse(self):
>         is_low = self['low'] is not None
>         is_high = self['high'] is not None
>         is_unit = self['unit'] is not None
>         if is_high and not is_low:
>             self.error = "Must provide low number."
>         if (is_low or is_high) and not is_unit:
>             self.error = "Must provide unit."

The _parse needs to set the value to something.

>
> I made a date widget earlier but that was pretty straightforward,
> since
> the value is a datetime object, and I put the subwidgets
> in .year, .month,
> and .day attributes.  (Perhaps I should have used .add()
> and .widgets, but
> I bypassed them.)  But a range object doesn't have an obvious
> single value
> unless I arbitrarily say  ".value = (low, high, unit)".  Is that
> how to do
> it with composite widgets?

Yes.  Or, you could make a RangeWithUnit class for this purpose.
You might be interested in the classes for this that are in dulcinea.
They serve a similar purpose, but the widgets don't work the same
way as the ones you want.

>
> After that I need to make a latitude/longitude widget that accepts:
>     123.45               West    (degrees)
>     123     45.67        West    (degrees, minutes)
>     123     45    45.67  West    (degrees, minutes, seconds)
> But first I have to get the simpler widget down.

That will be easier after you get the pattern worked out.

>
> What is the purpose of WidgetList and WidgetDict?  At first I
> thought they
> were for making arbitrary composite widgets, but that raises the
> question
> of when to use them and when to use CompositeWidget directly, and what
> that funny 'add_element' widget is for.  Then I thought, "No, they are
> specialized widgets, for growable lists/dicts."  Are they for when you

That thought was correct.

> have multiple values and want to let the user as many additional
> values as
> they want?  But there's nothing to delete an element if they want
> to go
> the other way.  Or are these widgets for something else?

Dulcinea has a DeletableWidget that is designed to allow delete buttons
in a WidgetList.