我需要为没有特定功能的用户限制媒体库中的项目。有很多例子可以说明如何将它们限制为仅限于给定用户上传的项目，但我的需要比这更复杂。

我需要将没有特定功能的用户的媒体项目限制为以下附件：

标题图像（即在外观>标题中设置）

下面是我提出的解决方案。

/*
 * restrict media items available to users without cap=mycap to those that are NOT:
 *
 * 1. theme headers (i.e., set in Appearance > Headers)
 * 2. page thumbnails (i.e., featured images)
 */
add_action (\'pre_get_posts\', \'restrict_media\') ;
function
restrict_media ($query)
{
    if (!is_admin () || $query->get (\'post_type\') != \'attachment\' ||
            current_user_can (\'mycap\')) {
        return ;
        }

    // get our theme\'s headers (i.e., set in Appearance > Headers)
    $args = array (
        \'post_type\' => \'attachment\',
        \'post_status\' => array (\'inherit\', \'private\'),
        \'posts_per_page\' => -1,
        \'meta_query\' => array (
            \'relation\' => \'AND\',
            array (
                \'key\' => \'_wp_attachment_context\',
                \'value\' => \'custom-header\',
                ),
            array (
                \'key\' => \'_wp_attachment_is_custom_header\',
                \'value\' => \'antelopevalley\',
                ),
            ),
        ) ;
    // remove ourself from pre_get_posts to avoid infinite regression
    remove_action (\'pre_get_posts\', array ($this, \'restrict_media\')) ;
    $headers = new WP_Query ($args) ;
    // get the IDs of the headers
    $header_ids = array_map (function ($p) { return ($p->ID) ; }, $headers->posts) ;

    // add ourself back to pre_get_posts for subsequent queries
    add_action (\'pre_get_posts\', array ($this, \'restrict_media\')) ;

    // get posts with thumbnails
    $args = array (
        \'post_type\' => \'page\',
        \'post_status\' => array (\'publish\', \'pending\', \'draft\', \'private\'),
        \'posts_per_page\' => -1,
        \'meta_query\' => array (
            array (
                \'key\' => \'_thumbnail_id\',
                \'compare\' => \'EXISTS\',
                ),
            ),
        ) ;
    $with_thumbnail = new WP_Query ($args) ;
    // get the IDs of the thumbnails
    $thumbnail_ids = array_map (function ($p) { return (get_post_meta ($p->ID, \'_thumbnail_id\', true)) ; },
        $with_thumbnail->posts) ;

    // exclude all theme headers and thumbnails
    $query->set (\'post__not_in\', array_merge ($header_ids, $thumbnail_ids)) ;

    return ;
}

上述解决方案有效；然而，这对我来说似乎太复杂了！

我想知道是否有人能提出一个更简单的解决方案。

注意：我以前尝试过post{where，join}过滤器来满足其他需求，但发现它们太复杂，无法维护，所以我甚至没有尝试使用它们来解决这个问题，但我对使用它们的人非常开放