DTML Basics (part 2) - Submitting To The King
( Page 8 of 8 )

You'll have noticed that in all the examples shown thus far, we've used two Zope objects - a single DTML Document containing the form, and a separate DTML Method which processes the form input and generates appropriate output. However, DTML provides an elegant method to combine those two pages into one via the "submit" variable.

In order to better understand this, create a new DTML Document named "DualPurposeForm" and add the following DTML code to it:

<dtml-var standard_html_header>



<dtml-if submit>



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-else submit>



<form action="DualPurposeForm" method="POST">

Species:

<br>

<input name="species">

<p>

Home planet:

<br>

<input name="planet">

<p>

Distance (light years) from Earth: 

<br>

<input name="distance">

<p>

<input type="Submit" name="submit" value="Beam Me Up, Scotty"> </form>



</dtml-if>



<dtml-var standard_html_footer>

In this case, the DTML "if" test will first check to see if the "submit" form variable exists. If it does, it implies that the form has been submitted, and the second half of the script, the actual form processor, comes into play. If it doesn't, it implies that the form has not yet been submitted, and so the initial, empty form is displayed.

This technique makes it possible to reduce the number of objects used, and perhaps make your Zope object collection easier to handle.

And that's about it for the moment. In this article, you learnt a little more about DTML, specifically about how to introduce decision-making logic into your Methods with DTML's numerous conditional statements. You learnt about the "if" and "unless" series of conditional statements, and saw a few examples of the different variants possible. Finally, you saw how all that theory can be put to practical use by implementing a simple form processor for use on a Web page.

In the next issue of DTML Basics, I'll be rounding out the fundamentals with a look at the various loop constructs provided by DTML. As with everything you've seen so far, DTML comes with its own twist (pardon the pun) on the traditional way of implementing loops. Come back next time to see what I'm talking about...and, until then, go practise.

Note: All examples in this article have been tested on Linux/i586 with Zope 2.5.0. Examples are illustrative only, and are not meant for a production environment. Melonfire provides no warranties or support for the source code described in this article. YMMV!

>>> More Zope Articles          >>> More By Harish Kamath, (c) Melonfire