get posts based on meta value of the author

Question

Say I have a user meta field that is called "meta1". I want to get posts (via get_posts or the like) who's author meta1 = true. Any idea how I should approach this?

Answer 1

Get for all users / authors with user meta field. meta1 = true

$args = array(
    'meta_key'     => 'meta1',
    'meta_value'   => 'true',
    'meta_compare' => '=',
    'fields'       => 'all',
 );
$users = get_users( $args );

Store user id and login into an array authors

$authors = array();
foreach ( (array) $users as $user ) {
  authors[ $user->ID ] = $user->user_login;
}

Now you can pass authors in your posts query.

$posts = query_posts( array( 'author__in'=> array_keys( $authors ) ) );

Or

$posts = new WP_Query( array( 'author__in' => array( array_keys( $authors ) ) );

Final code

$args = array(
    'meta_key'     => 'meta1',
    'meta_value'   => 'true',
    'meta_compare' => '=',
    'fields'       => 'all',
 );
$users = get_users( $args );
$authors = array();
foreach ( (array) $users as $user ) {
    $authors[ $user->ID ] = $user->user_login;
}
$query = new WP_Query( array( 'author__in' => array( array_keys( $authors ) ) );

if ( $query->have_posts() ) : while( $query->have_posts() ) : $query->the_post();

//print post contents, title etc

endwhile;
endif;
wp_reset_postdata();

Answer 2

This can be accomplished via the parse_query filter, as follows:

add_action ('parse_query', array ($this, 'wpse_private_author_query')) ;

function
wpse_private_author_query ($query)
{
    // get our private author query query_var   
    $private_author_query = $query->get ('_private_author_query') ;
    if (empty ($private_author_query)) {
        // our private author query query_var is not set, so bail without modifying $query
        return ;
        }

    $args = array (
        'fields' => 'ID',
        ) ;
    $args = wp_parse_args ($args, $private_author_query) ;
    // get the ID's of the users that match our private author query
    $users = get_users ($args) ;

    // unset our private author query query_var
    unset ($query->query_vars['_private_author_query']) ;

    // add the author IDs to the query
    $query->set ('author__in', $users) ;

    return ;
}

To see this in action, we can do:

$args = array (
    'post_type' => 'any',
    'post_status' => 'public',
    '_private_author_query' => array (
        'meta_key' => 'meta1',
        'meta_value' => true,
        'meta_compare' => '=',
        ),
    ) ;
$posts = new WP_Query ($args) ;

Note: the above is more general than your question. You asked just for user_meta, but the above will allow searching by any of the characteristics supported by WP_User_Query::parse_query(). For example, we can also do:

$args = array (
    'post_type' => 'any',
    'post_status' => 'public',
    '_private_author_query' => array (
        'role' => 'editor',
        ),
    ) ;
$posts = new WP_Query ($args) ;

etc.

Answer 3

You can define it in the loop's arguments and i believe it will work with other WP functions as well

$args = array(
  'author' => 1 // Author's ID
);