farm_area.install

<?php
/**
 * @file
 * Farm area install.
 */

/**
 * Update allowed values in the farm area types field.
 */
function farm_area_update_7000() {

  // Load the farm area type field info.
  $area_type_field = field_info_field('field_farm_area_type');

  // Set the allowed values to an empty array.
  $area_type_field['settings']['allowed_values'] = array();

  // Point to the new allowed values function.
  $area_type_field['settings']['allowed_values_function'] = 'farm_area_type_options';

  // Update the field.
  field_update_field($area_type_field);
}