Re: [Webmacro-devel] New features for 2.0?

[Keats <ke...@xa...>]

----- Original Message ----- 
From: "Eric Ridge" <eb...@tc...>

> > 3) #try directive
>
> <snip>
>
> > I remember Eric saying he did this a while ago, but then Brian talked
> > him
> > out of it.  I'd like to hear the reasoning.  I find it quite useful for
> > validation and debugging.
>
> Reason being that nothing you do in a template should actually throw an
> exception.  And if it does, you want it reported.  I see this as very
> similar to the "On Error Resume Next" construct of VisualBasic... very
> very bad.

I've been mulling this over and I suppose you're right -- try/catch
functionality isn't really needed.

I was primarily thinking about using this for forms processing.  This would
allow me to do things like validate user-entered numbers and dates within a
template (without relying on JavaScript).  Of course I can write utilities
to do this, e.g., $isInt() or $isDate().  The down-side is that *valid*
input has to get parsed twice -- once to validate, and once to get the
value.  I suppose this is pretty negligible compared to the normal latency
of a request.

Another approach might be to change the casting functions to return objects
instead of primitives.  E.g.,
   Integer toInt(Object o);
instead of
   int toInt(Object o);

Then I could just return null values instead of throwing exceptions:

   #set $age=$toInt($Form.age)
   #if (!$age){ Invalid age entered ($Form.age).  }

Since WM uses auto-boxing and unboxing of primitives anyway, this may
actually be slightly more efficient.

Hmmm ...

Keats