At 06:13 10/05/2002, zope-dev-request@zope.org wrote:
'else' is tricky within the block oriented structure of anything XML-ish, because of the concept of 'well-formedness'. The 'if' statement would have to be singly wrapped, and the else block wrapped separately, looking at least somewhat awkward any way you go about it. The best I can come up with in my mind is this, in order to have the 'else' pick up on the condition expressed in its surrounding container. But, yuck:
<if ...> true stuff <else> false stuff </else> </if>
A good page template way is something like this:
<tal:if condition="myTalesExpression"> truth </tal:if> <tal:else condition="not:myTalesExpression"> false </tal:else>
The 'not' TALES namespace is valuable. The downside is that you evaluate the expression twice. A good way to work within this is something that I did earlier today, outside of this conversation, where I evaluate an expression earlier and assign it to a variable:
<div id="edit-area" tal:define="editItems python:here.getMenuItem(...)">
<h3>Edit Menu Items</h3> <form action="Delete" method="post" name="actForm" tal:condition="editItems">
... (form and table elements, and a loop over editItems contained in here if there were results) ...
</form>
<div class="emph" tal:condition="not:editItems"> No menu items available </div>
</div>
This is something I did a lot in DTML too, setting a search result to either a global variable, or inside of a large <dtml-let> namescape
It is maybe not clear that the above is really usable and allowed. I do not know how and where to stress that the tal: marked tags are underdocumented what a pity. I have already tried : http://www.zope.org/Documentation/ZopeBook/AdvZPT.stx#3-44 Sorry that I am not able to explain it better... -- Godefroid Chapelle BubbleNet sprl rue Victor Horta, 18 / 202 1348 Louvain-la-Neuve Belgium Tel + 32 (10) 459901 Mob + 32 (477) 363942 TVA 467 093 008 RC Niv 49849