Wsrtjtyk

In Wordpress:

I have a need to exclude a certain category of posts from the main WP loop. But only if that post has no other categories.

For example, if the category in question was called X...

Test 1: A post which belongs to only X category would be excluded.

Test 2: A post which belongs to X and Y categories would be included.

Test 3: Posts which belong to Z or Foo or anything else would also be included.

I have the following code so far:

function exclude_category( $query ) {

    if ( $query->is_home() && $query->is_main_query() ) {

    $query->set( 'cat', '-271' );

    }

}



add_action( 'pre_get_posts', 'exclude_category' );

But this works for test 1 and 3 (above) but not test 2. How can I modify the query to achieve this?

I thought up a way to do this, though I am not sure it is the best way.

Basically I am asking WP for a list of all categories then I am concatenating a list of those categories minus the one which I want to exclude. I then feed that into the 'cat' parameter in the WP Query. It seems to work as I would hope, but it also seems a little round-about. I would appreciate any feedback.

In this case 271 is the id for my x category.

function exclude_category( $query ) {



    $terms = get_terms( array(

        'taxonomy' => 'category',

        'hide_empty' => false,

    ) );



    $catquery = "";

    foreach($terms as $term) {

        if($term->term_id != 271) {

            $catquery .= $term->term_id . ",";

        }

    }



    $catquery = substr($catquery, 0, -1);



    if ( $query->is_home() && $query->is_main_query() ) {

         $query->set( 'cat',  $catquery  );

    }

}



add_action( 'pre_get_posts', 'exclude_category' );

EDIT

I ended up changing it to a taxonomy query so I could set include_children to false.

function exclude_category( $query ) {



    $terms = get_terms( array(

        'taxonomy' => 'category',

        'hide_empty' => false,

    ) );



    $catarray = ;

    foreach($terms as $term) {

        if($term->term_id != 271) {

            array_push($catarray, $term->term_id);

        }

    }



    if ( $query->is_main_query() &&  $query->is_home()) {

         $query->set( 'tax_query', array(  array(

             'taxonomy' => 'category',

             'field' => 'term_id',

             'terms' => $catarray,

             'include_children' => false

            )));

    }

}



add_action( 'pre_get_posts', 'exclude_category' );

I would assume that including all category y, will include all posts contained in x and also in y.