query_posts with meta_value

Question

I have category 'news' http://localhost/foldername/news, for each 'news' posts I have custom field called 'years' and is set up as a Text Field. I have 2 values assigned n different posts '2013' and '2014'.

What I'm trying to do first to show only 2014 posts in 'news' category http://localhost/foldername/news and second to pass url parameter so if I want to show '2013' to use the following http://localhost/foldername/news/?years=2013

I have selected Attribute so user will select which year posts to show but as default will show 2014 posts

 <select>
  <option value="2014">2014</option>
  <option value="2013">2013</option>
</select>

For the first I found the following solution to show only '2014' posts in 'news' http://localhost/foldername/news:

    $args= array(   
    'meta_key' => 'years',
    'meta_value' => '2014',
    );
   query_posts($args);

Now my big problem is that I pass the parameter to show '2013' posts but is not working

Tried something like this:

function wpse129223_custom_meta_query( $query ) {

    // If not on the main query, or on an admin page, bail here
    if ( ! $query->is_main_query() || is_admin() ) {
    return;
}

// If 'type' isn't being passed as a query string, bail here
if ( empty( $_GET['years'] ) ) {
    return;
}

// Get the existing meta query, cast as array
$meta_query = (array) $query->get('meta_query');

    // Convert 'type' into an array of types
    $types = explode( ',', $_GET['years'] );

    // Ensure that types aren't empty
    if ( is_array( $types ) && ! empty( $types ) ) {

        // Build a meta query for this type
        $meta_query[] = array(
            'key'     => 'years',
            'value'   => $types,
            'compare' => 'IN',
        );

        // Update the meta query
        $query->set( 'meta_query', $meta_query );
    } 

}
add_action( 'pre_get_posts', 'wpse129223_custom_meta_query' );

But every time I go to http://localhost/foldername/news/?years=2013 still shows me '2014' posts

Answer 1

Per comments, just use pre_get_posts filter (no query_posts()) very much as you have it with a few adjustments, eg test for $query->is_category( 'news' ) so that it only runs on news queries, and set the default to "2014" rather than bailing on no $_GET, eg

function wpse129223_custom_meta_query( $query ) {

    // If not on the main query, or on an admin page, bail here
    if ( ! $query->is_main_query() || is_admin() || ! $query->is_category( 'news' ) ) {
        return;
    }

    // Get the existing meta query, cast as array
    $meta_query = (array) $query->get('meta_query');

    // Convert 'type' into an array of types
    $types = explode( ',', empty( $_GET['years'] ) ? '2014' : $_GET['years'] );

    // Ensure that types aren't empty
    if ( is_array( $types ) && ! empty( $types ) ) {

        // Build a meta query for this type
        $meta_query[] = array(
            'key'     => 'years',
            'value'   => $types,
            'compare' => 'IN',
        );

        // Update the meta query
        $query->set( 'meta_query', $meta_query );
    } 

}
add_action( 'pre_get_posts', 'wpse129223_custom_meta_query' );