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If Only... - Zope

In this second article, dive a little deeper into theintricacies of DTML by getting up close and personal with conditionalstatements and comparison operators. This article discusses thedifferent variants of the "if" statement available in DTML, togetherwith examples and code listings that demonstrate how they can be used ina Web applications.

  1. DTML Basics (part 2)
  2. If Only...
  3. Comparing Apples And Oranges
  4. Welcome To The Matrix
  5. Celluloid Dreams
  6. Paring It Down
  7. Deeper And Deeper
  8. Submitting To The King
By: Harish Kamath, (c) Melonfire
Rating: starstarstarstarstar / 4
June 05, 2002

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The first - and simplest - decision-making routine isthe "if"statement, which generally looks like this:

<dtml-if id>
do this!
The "condition" here refers to a conditional expression, which evaluatesto either true or false.

Let's look at a piece of code to understand this better. Here's a DTMLMethod named "ifOnly", created in the same "DTML Basics" folder I usedlast time.

<dtml-if id>
<p>Variable "id" exists and has the value <dtml-var id>.</p> </dtml-if>

<dtml-if myName>
<p>Variable "myName" exists and has the value "<dtml-var myName>".</p>
Now, when you view the output of this Method, you should see thefollowing:

Variable "id" exists and has the value DTML Basics.
If you take a close look at the code above, you'll see that it includestwo "if" statements; however, only one is displayed in the output. Thisis because the first statement evaluated to a true value, because thevariable "id" exists and has a value (the name of the container withinwhich the DTML Method is stored). However, the second DTML variable"myName" does not exist. As a result, the corresponding "if" statementevaluates as false, and so, the text enclosed within the<dtml-if> blockis not displayed.

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

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