Generic function for adding custom taxonomy to the filter bar

[Frederick]

Hi,

I had been searching around the forums and saw a bunch of custom implementations, and (thanks to that) using very little effort cobbled together a drop-in set of code (basically taking the category template and modifying a single variable twice) that you can use to easily add as many taxonomies as you want to the filter bar:

if (class_exists('Tribe__Events__Filterbar__Filter')):
 class Tribe__Events__Filterbar__Custom extends Tribe__Events__Filterbar__Filter {
 	public $type = 'select';

 	public function get_admin_form() {
 		$title = $this->get_title_field();
 		$type = $this->get_multichoice_type_field();
 		return $title.$type;
 	}

 	protected function get_values() {
 		$terms = array();

 		// Load all available event categories
 		$source = get_terms( $this->slug, array( 'orderby' => 'name', 'order' => 'ASC' ) );
 		if ( empty( $source ) || is_wp_error( $source ) ) return array();

 		// Preprocess the terms
 		foreach ( $source as $term ) {
 			$terms[ (int) $term->term_id ] = $term;
 			$term->parent = (int) $term->parent;
 			$term->depth = 0;
 			$term->children = array();
 		}

 		// Initally copy the source list of terms to our ordered list
 		$ordered_terms = $terms;

 		// Re-order!
 		foreach ( $terms as $id => $term ) {
 			// Skip root elements
 			if ( 0 === $term->parent ) continue;

 			// Reposition child terms within the ordered terms list
 			unset( $ordered_terms[ $id ] );
 			$term->depth = $terms[ $term->parent ]->depth + 1;
 			$terms[ $term->parent ]->children[ $id ] = $term;
 		}

 		// Finally flatten out and return
 		return $this->flattened_term_list( $ordered_terms );
 	}

 	/**
 	 * Flatten out the hierarchical list of event categories into a single list of values,
 	 * applying formatting (non-breaking spaces) to help indicate the depth of each nested
 	 * item.
 	 *
 	 * @param array $term_items
 	 * @param array $existing_list
 	 * @return array
 	 */
 	protected function flattened_term_list( array $term_items, array $existing_list = null ) {
 		// Pull in the existing list when called recursively
 		$flat_list = is_array( $existing_list ) ? $existing_list : array();

 		// Add each item - including nested items - to the flattened list
 		foreach ( $term_items as $term ) {
 			$flat_list[] = array(
 				'name'  => str_repeat( ' ', $term->depth * 2 ) . $term->name,
 				'value' => $term->term_id,
 				'data'  => array( 'slug' => $term->slug ),
 				'class' => 'tribe-events-category-' . $term->slug,
 			);

 			if ( ! empty( $term->children ) ) {
 				$child_items = $this->flattened_term_list( $term->children, $existing_list );
 				$flat_list = array_merge( $flat_list, $child_items );
 			}
 		}

 		return $flat_list;
 	}

 	/**
 	 * This method will only be called when the user has applied the filter (during the
 	 * tribe_events_pre_get_posts action) and sets up the taxonomy query, respecting any
 	 * other taxonomy queries that might already have been setup (whether by The Events
 	 * Calendar, another plugin or some custom code, etc).
 	 *
 	 * @see Tribe__Events__Filterbar__Filter::pre_get_posts()
 	 *
 	 * @param WP_Query $query
 	 */
 	protected function pre_get_posts( WP_Query $query ) {
 		$new_rules      = array();
 		$existing_rules = (array) $query->get( 'tax_query' );
 		$values         = (array) $this->currentValue;

 		$new_rules[] = array(
 			'taxonomy' => $this->slug,
 			'operator' => 'IN',
 			'terms'    => $values,
 		);

 		/**
 		 * Controls the relationship between different taxonomy queries.
 		 *
 		 * If set to an empty value, then no attempt will be made by the additional field filter
 		 * to set the meta_query "relation" parameter.
 		 *
 		 * @var string $relation "AND"|"OR"
 		 */
 		$relationship = apply_filters( 'tribe_events_filter_taxonomy_relationship', 'AND' );

 		/**
 		 * If taxonomy filter meta queries should be nested and grouped together.
 		 *
 		 * The default is true in WordPress 4.1 and greater, which allows for greater flexibility
 		 * when combined with taxonomy queries added by other filters/other plugins.
 		 *
 		 * @var bool $group
 		 */
 		$nest = apply_filters( 'tribe_events_filter_nest_taxonomy_queries',
 			version_compare( $GLOBALS['wp_version'], '4.1', '>=' )
 		);

 		if ( $nest ) {
 			$new_rules = array(
 				__CLASS__ => $new_rules,
 			);
 		}

 		$tax_query = array_merge_recursive( $existing_rules, $new_rules );

 		// Apply the relationship (we leave this late, or the recursive array merge would potentially cause duplicates)
 		if ( ! empty( $relationship ) && $nest ) {
 			$tax_query[ __CLASS__ ][ 'relation' ] = $relationship;
 		} elseif ( ! empty( $relationship ) ) {
 			$tax_query[ 'relation' ] = $relationship;
 		}

 		// Apply our new meta query rules
 		$query->set( 'tax_query', $tax_query );
 	}
 }
endif;

Every taxonomy you want to add is:

new Tribe__Events__Filterbar__Custom('Taxonomy Name','tax_slug');

I would advise putting these before the endif.

That’s all. Hope this helps someone else.

[Andras]

Hi Frederick,

Wow, supercool stuff!!! Thanks for sharing this, I’m sure it will be useful for others as well.

Keep rockin’!

Cheers,
Andras

[Author]

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