pre_get_posts to get all posts connected to single object

This topic contains 16 replies, has 2 voices, and was last updated by Clayton Collie 7 months, 3 weeks ago.

Creator
Topic
October 18, 2018 at 4:59 AM #11651
Resolved
Clayton Collie
Participant
I have a listing of people that I am showing on the post type archive. For taxonomies I can use a simple query var with the taxonomy term to filter out the listing of all posts into the posts only inside that taxonomy. I would like to do the same thing with relationships.
Is there a built-in query var for relationships? I think that is relationship. But then how would I use it in the URL bar? Pass a single ID?
for example – domain.com/people/?relationship=320
What I was thinking about doing is add a custom query arg then pass a single post ID then use that post ID inside a pre_get_post filter to only show the posts related to that ID. Does that sound like a good plan?
```
function custom_query_vars_filter($vars) {
    $vars[] .= 'relationships';
    return $vars;
}
add_filter( 'query_vars', 'custom_query_vars_filter' );
```
```
function prefix_get_related_posts( $query ) {
    
    $post_id = get_query_var('relationships');
    
    if ( empty( $post_id ) || is_admin() ) {
        return $query;
    }

    if( is_post_type_archive( 'poa_person' ) && $query->is_main_query() ) {
        $relationship = array( 
            'id' => 'poa_practice_to_poa_person',
            'from' => $post_id,
        );
        $query->set( 'relationship', $relationship );
        }

    return $query;
}
add_filter( 'pre_get_posts', 'prefix_get_related_posts', 10, 1);
```
This does not work just yet. Can you help shed some light on this query?
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October 18, 2018 at 4:36 PM #11659

Anh Tran
Keymaster
Hi Juanita,
You’re right about the query var. And your idea of adding the query var is great. I think the only problem is using pre_get_posts is too late. The plugin uses parse_query hook to setup some parameter for the SQL. So you might want to change your code from pre_get_posts to parse_query.
October 18, 2018 at 8:52 PM #11663
Clayton Collie
Participant
```
function custom_query_vars_filter($vars) {
    $vars[] .= 'relationships';
    return $vars;
}
add_filter( 'query_vars', 'custom_query_vars_filter' );

function prefix_get_related_posts( $query ) {
    
    $post_id = get_query_var('relationships');
    
    if ( empty( $post_id ) || is_admin() ) {
        return $query;
    }

    if( is_post_type_archive( 'poa_person' ) && $query->is_main_query() ) {
        $query->set( 'relationship', 
            array( 
                'id' => 'poa_practice_to_poa_person',
                'from' => $post_id,
            )
        );
    }

    return $query;
}
add_filter( 'parse_query', 'prefix_get_related_posts', 10, 1);
```
parse_query works great. But now my styling is all jacked up. At least the query is working now. Thanks for the help.
October 18, 2018 at 10:13 PM #11664

Clayton Collie
Participant
On second look, parse_query is throwing off the entire query so the post type archive doesn’t even get the post type it is associated with. I am getting the proper related post just fine but I am loosing the post type for the entire query. It seems like I am overriding my entire query and just setting the relationship query instead of adding the two queries together.
October 20, 2018 at 8:18 AM #11683

Anh Tran
Keymaster
Hi Juanita,
The parse_query hook runs just before pre_get_posts and there’s nothing between them. See this screenshot:
View post on imgur.com
So, if your code works with pre_get_posts, it should work with parse_query. I guess the problem might come from other things.
October 20, 2018 at 11:37 PM #11694
Clayton Collie
Participant
I disabled every plugin and reverted to default WP theme to test. I am still stumped. Have a look at the two screenshots. First one is the base query where the query and query_vars match. This query assigns the post type to every other function to get things like post type archive title, etc.

Second is when the query_vars are used to alter the query. Notice how the query and query vars are different. The filtering of posts works great to show only the post that is related to 2735.

Can you add this code to your install and let me know if you are seeing the same errors?
```
add_action( 'parse_query', 'poa_filter_query_by_relationship', 10, 1 );
/**
 * Filter the main query by using URL parameters
 * 
 * @param object $query WP_Query.
 * @return object
 * 
 * @since 3.6.8
 */

function poa_filter_query_by_relationship( $query ) {
    
    $id     = get_query_var('relation_id');
    $from   = get_query_var('relation_from');
    $to     = get_query_var('relation_to');
    
    if ( ! empty( $id ) && ! is_admin() && $query->is_main_query() ) {

        if ( ! empty( $from ) ) {
            
            $query->set( 'relationship', 
                array( 
                    'id'  => esc_attr( $id ),
                    'from'    => intval( $from ),
                )
            );

            var_dump($query);

        } elseif ( empty( $to ) ) {

            $query->set( 'relationship', 
                array( 
                    'id'  => esc_attr( $id ),
                    'to'  => intval( $to )
                )
            );
        }
        
    }

}
```
```
add_filter( 'query_vars', 'add_query_vars' );
/**
     * Add query vars to build query with URL parameters
     *
     * @param array $vars WP_Query variables.
     * @return array
     * @since 3.6.8
     */
    public function add_query_vars( array $vars ) {
        $vars[] = 'relation_id';
        $vars[] = 'relation_from';
        $vars[] = 'relation_to';
        return $vars;
    }
```
October 22, 2018 at 4:56 PM #11702
Anh Tran
Keymaster
Hi Juanita,
I can’t see 2 screenshots :(.
But I think the problem is the way you get query var. The get_query_var should not be used in this situation as it gets the value from the main query. Please replace the code with:
```
$id = $query->get('relation_id');
$from = $query->get('relation_from');
$to = $query->get('relation_to');
```
October 23, 2018 at 3:22 AM #11715

Clayton Collie
Participant
Still not working even thought changed how I am getting the query_var.
Did you try running that code a post type archive? That is what I am doing and seeing part of the query being altered. Its weird. It shows the proper post type objects but doesnt have the proper values for sending the post type to things like post_type_archive_title.
October 23, 2018 at 3:24 AM #11716

Clayton Collie
Participant
October 23, 2018 at 3:25 AM #11717

Clayton Collie
Participant
altered query
base query
October 25, 2018 at 2:47 PM #11746

Anh Tran
Keymaster
Hi Juanita,
Sorry to get back late. I tried your code and created a video on that: http://recordit.co/BlAq5rhUVr. The query seems fine to me. Please take a look.
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