How do I switch node templates based on arbitrary critera

Question

I'm trying to switch the node template file based on a variable, in drupal 6 you could simply set $vars['template_file'] = 'node-whatever'; from with the preprocess_node() and name the new node template file node-whatever.tpl.php. I drupal 7 this is gone. I looked through the docs and it appears that in Drupal 7 its $vars['theme_hook_suggestion'][] = 'node--whatever'; but this is not working for me. Am I doing something wrong? is there a naming convention that I'm missing? The documentation is a little confusing

Answer 1

Indeed, in D7 the template suggestions are an array of suggestions, in the order of importance. You've got 99% of it, but your dashes need to be underscores. Try:

function THEME_preprocess_page() {
  $vars['theme_hook_suggestions'][] = 'page__whatever';
}

function THEME_preprocess_node() {
  $vars['theme_hook_suggestions'][] = 'node__whatever';
}

Why underscores instead of hyphens? From the Drupal API docs:

  // Hyphens (-) and underscores (_) play a special role in theme suggestions.
  // Theme suggestions should only contain underscores, because within
  // drupal_find_theme_templates(), underscores are converted to hyphens to
  // match template file names, and then converted back to underscores to match
  // pre-processing and other function names. So if your theme suggestion
  // contains a hyphen, it will end up as an underscore after this conversion,
  // and your function names won't be recognized.

Answer 2

Some Drupal 7 example where you're loading different TPL template based on taxonomy term wich Page has (field_page_category):

/**
 * Override or insert variables into the node templates.
 *
 */
function phptemplate_preprocess_node(&$vars, $hook) {
  $node = $vars['node'];
  switch($node->type) {
    case 'page':
      $tid = $node->field_page_category[LANGUAGE_NONE][0]['taxonomy_term']->tid;
      $parents = taxonomy_get_parents_all($tid);
      foreach ($parents as $tid => $term) {
        $category = ereg_replace('[[:space:]]', '-', $term->name);
        // Suggest a theme name, see: https://drupal.org/node/1089656
        $vars['theme_hook_suggestions'][] = 'node__page__'. strtolower($category);
      }
    break;
  } // end: switch
}