I have created a custom content type with three decimal fields. I need to tally these three fields and then wrap the output of each one with a specific data attribute, stating their respective value as a percentage of the total.
Am new to drupal so if someone could point me in the right right direction as to how best achieve this it would be much appreciated.
This question is tagged with Views, so I'm just going to go out on a limb and leave this here just in case: Views Calc
This module adds simple calculations to a views table. Requires the Views module.
You can SUM, AVERAGE, COUNT, MIN, MAX, or AVG selected columns. A plug in theme makes the view look more spreadsheet-like (right justifies numeric fields, shades calculated columns and rows, and underlines calculated rows).
The standard method to set up variables and pass them to a template file is through the use of a preprocess function. In the case of the node.tpl.php file this would look something like:
function MYTHEME_preprocess_node(&$vars) {
$field_1_items = field_get_items('node', $node, 'field_something');
$field_2_items = field_get_items('node', $node, 'field_something_else');
$computed_value = $field_1_items[0]['value'] + $field_2_items[0]['value'];
$vars['computed_value'] = $computed_value;
}
Then in your template file you could do something like:
<div class="some-class">
<?php echo $computed_value; ?>
</div>
That's just an example, your use case will likely differ significantly; but that's the basic method behind it.
Remember that the template files should only ever be used for presentation (adding HTML markup and outputting PHP variables that have been prepared elsewhere), never for logic. The only exception to this is conditional logic (if/switch statements) and other basic logical operations such as &&, ||, etc. As you're performing a calculation on field results you're implementing logic, so using a preprocess function is the correct method in my opinion.
It might seem like a small thing, but separating your presentation and logic will stand you in good stead for future development. If you don't do it you'll end up with a messy code base and future maintenance will be harder than it needs to be :)
if contains boolean calculations and I've seen a lot of ifs in core's .tpl.php files. Things like this one can be either in data, logic or presentation, depending on intended use, can't they? As long as the author is consistent about it in his project, he should be all right. (I upvoted your answer, by the way)
If you consider this to be a presentation issue, best place for this operation is node.tpl.php (or analogous template for content type with fields in question) in your custom theme.
If you consider it a second set of actual data, the way to go is Computed Field module or similar solution.
