Loop De Loop

This month I thought I'd take a look at one of the more common template variables available to nearly all assets in WebGUI, the Loop.  I'm sure that most folks who have templated in WebGUI know what a loop is, but there a couple of things that can be done with them that maybe you never considered.

1)Test if data is present.  Did you know that you can do a basic true false test against a loop just to see if there's anything even in it? This is extremely handy in those cases where you don't want anything to happen if there isn't any data at all in a Loop.  Here's an example with a Collaboration System  asset.


<tmpl_if attachment_loop>
    <tmpl_loop attachment_loop>
        <tmpl_if __FIRST__>
            <div class=”attachments”>
        </tmpl_if>
            <div><a href=”<tmpl_var.page.url>”><tmpl_var page.title></a></div>
        <tmpl_if __LAST__>
            </div>
        </tmpl_if>
    </tmpl_loop>
</tmpl_if>


With this method, a surrounding div can be placed around all of the attachments which can allow additional styles to be used. But even beyond that, if there are no attachments, nothing at all happens- which is exactly what we'd want if nothing was attached.  But look beyond this simple example- a Search template could be modified to display “No Results Found” instead of loading a blank page. Or perhaps if no files are loaded within a Photo Gallery a message could be displayed that it's currently empty and photos need to be added. There are plenty of options to explore, particularly because loops are so prevalent in WebGUI assets.


2) Run loops more than once. I'm not sure if it's a little known fact or if people worry that it'll break their templates, but I rarely see anyone using the same loop twice in a template. At first glance, the need for that is probably not all that obvious, but there are some great reasons why to reuse a loop. Lets take a look a Navigation asset.

<tmpl_loop page_loop>
    <tmpl_if page.isCurrent>
        <div class=”navTitle”><tmpl_var page.title></div>
    </tmpl_if>
</tmpl_loop>

<div class=”mainNav”>
    <tmpl_loop page_loop>
        <div class=”navItem”><a href=”<tmpl_var page.url>”><tmpl_var page.title></a></div>
    </tmpl_loop>
</div>

With this example, whatever the title of the page is will be displayed on top of all of the other navigation items. This is a simple example, but there are far more complex applications with this method. Imagine being able to sort files in a Folder asset by type using HTML::Expr (which is a topic for another day), or creating Collaboration Systems that can sort by the author of the post.

I've heard some concern in the past about the hit to the server by using a loop twice in an asset, and the fact is that unless there is a ridiculous amount of information for that asset, there is little to worry about. So by all means, experiment!

Stay tuned. Next month I'm going to cover using CSS as a substitute for ten of your daily vitamin requirements.