Based on developer documents of get_comments
functions, it is using args like WP_Comment_Query::__construct
Method which is accepts post_id
in the argument’s array. So, the code will be like:
foreach($assignments as $assignment) {
echo $assignment->post_title;
$args = array(
'number' => 0,
'status' => 'approve',
// shows all comments, but it shouldn't
'post_id' => $assignment->ID
);
$comments = get_comments( $args );
if ( $comments ) {
foreach ( $comments as $comment ) {
echo '<li>';
echo $comment->comment_content;
echo '</li>';
}
}
}
Links:
https://developer.wordpress.org/reference/functions/get_comments/
https://developer.wordpress.org/reference/classes/wp_comment_query/__construct/