Hook for Field Duplication

Question

I have a custom module that is formatting the display of an image field, which can accept multiple values. I would like to know what hook I should use to duplicate the first value of the field (e.g. "[image1]"), and add it back to the beginning of the array (with array_unshift() I guess) before the rest of my functions format the display/theme of the field.

So what was

• [image1]
• [image2]
• [image3]

becomes

• [image1]
• [image1]
• [image2]
• [image3]

I am then going to theme them separately, but I think I already have that part figured out.

I am currently using hook_field_formatter_view(), and have tried to just add it to the beginning of the $items array at the top of the function, but that didn't seem to work. If I immediately dprint_r() the $items array after this it shows, but only 3 items get output; I am assuming that the number of field gets determined elsewhere.

Answer 1

You want hook_field_formatter_prepare_view() instead. Note this hook operate on a group of entities, not on a single one.

Here's a working snippet. Some array-fu is needed to not end up writing an ugly loop of ten lines, since deltas must be preserved linear.

<?php

function MODULE_field_formatter_prepare_view($entity_type, $entities, $field, $instances, $langcode, &$items, $displays) {
  foreach ($entities as $id => $entity) {
    $array = array(0 => $items[$id][0], 1 => $items[$id][0]);
    if (count($items[$id]) > 1) {
      array_splice($array, 2, 0, array_slice($items[$id], 1));
    }
    $items[$id] = $array;
  }
}

Answer 2

hook_field_formatter_view() is where your code makes the output that's shown to the user, and so it wants a renderable array as a return value. So just process the first image twice and give it a different css class or something.

Something like:

$output = array();
if (($field == 'myFieldType') && ($display == 'full')) {
  $output[] = renderFirstImage(reset($items));
  foreach ($items as $item) {
    $output[] = renderImage($item);
  }
}
return $output;

Since hook_field_formatter_view() expects a renderable array, and since renderable arrays are marked as rendered when they're rendered, simply making two references to the same object will cause one to be rendered, marked as rendered, and then subsequently ignored the next time.