json_api_filters_wp.php

<?php

/**
 * Attaches ACF fields to single posts
 *
 * Filters output from http://wordpress.org/extend/plugins/json-api/o
 * Requires ACF plugin
 */
function attach_acf_fields($response) {
  // We need ACF plugin
  if( !function_exists('get_fields') ) {
    return $response;
  }

  // Only do magic on single post
  if( !isset($response['post']) ) {
    return $response;
  }

  // Add fields to parent post
  add_acf_fields($response['post']);
  add_post_thumbnail($response['post']);

  // If this is a local guide, attach places post to the response
  if( $response['post']->type == 'local-guides' && isset($response['post']->acf_fields['places']) ) {
    add_related_posts($response['post'], 'places');
  }

  return $response;
}
add_filter('json_api_encode', 'attach_acf_fields');

/**
 * Adds all ACF fields to post object
 * @param post object
 * @return void
 */
function add_acf_fields(&$post){
  $post->acf_fields = get_fields($post->ID);
}

/**
 * Adds post thumbnail(s) to post object
 * @param post object
 * @return void
 */
function add_post_thumbnail(&$post, $sizes = false){
  // You can pass an array containing the sizes that you wish to retrieve. ie: array('thumbnail', 'large');
  if( isset($sizes) && $sizes == true && is_array($sizes) ) {
    $thumb_sizes = $sizes;
  }
  else {
    $thumb_sizes = get_intermediate_image_sizes();
  }
  foreach($thumb_sizes as $size) {
    $thumbs[$size] = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), $size );
  }
  $post->thumbnails = $thumbs;
}

/**
 * Add related posts and their all ACF fields and thumbs to post object
 * @param post object
 * @param string related_post_field
 * @return void
 */
function add_related_posts(&$post, $related_post_field){
  if( !isset($post->acf_fields[$related_post_field]) ){
    return;
  }
  foreach($post->acf_fields[$related_post_field] as &$related_post){
    add_acf_fields($related_post);
    add_post_thumbnail($related_post);
  }
}