Running On Empty - Zope

Finally, the "ignore_empty" directive tells Zope to ignore the form variable (exclude it from the variable space) if it's left empty. Here's an example:

<dtml-var standard_html_header>
<form action="FormProcessor" method="POST">
Species:
<br>
<input 
name="species:string:ignore_empty">
<p>
Home planet:
<br>
<input name="planet:ignore_empty">
<p>
Distance 
(light years) from Earth: 
<br>
<input name="distance:int:ignore_empty 
">
<p>
<input 
type="Submit" value="Beam Me Up, Scotty">
</form>
<dtml-var 
standard_html_footer>

In this case, if any of the fields are left empty and the form is submitted to the FormProcessor object, the corresponding DTML variable will never come into existence. Consequently, the FormProcessor object (which, you will remember, references each of these variables) will raise a KeyError when it attempts to access this non-existent variable.

Here's what it looks like:



Don't like this? You can fix it by telling Zope what to do if it encounters a missing variable by adding the "missing" attribute to the variable call in the form processor. Take a look at the new, improved FormProcessor:

<dtml-var standard_html_header>
Welcome to Earth, <b><dtml-var species 
missing="Alien"></b> from the
planet <b><dtml-var planet missing="Zorgo"></b>. 
<p>
How was your journey? Travelling <b><dtml-var distance missing="so
many"></b> 
light years must be quite a shock to the system. Why don't
you relax and have 
a drink?
<dtml-var standard_html_footer>

The "missing" attribute sets a default value for the variable in the event that Zope cannot find it, in an attempt to avoid those ugly error messages.

>>> More Zope Articles          >>> More By Team Melonfire, (c) Melonfire

blog comments powered by Disqus