APP_View

class-app-view.php

/**
 * Helper class for controlling all aspects of a view.
 *
 * Supported methods (automatically hooked):
 *  - init() - for registering post types, taxonomies, rewrite rules etc.
 *  - parse_query() - for correcting query flags
 *  - pre_get_posts() - for altering the query, without affecting the query flags
 *  - posts_search(), posts_clauses(), posts_request() - for direct SQL manipulation
 *  - the_posts() - for various other manipulations
 *  - template_redirect() - for enqueuing scripts etc.
 *  - template_include( $path ) - for loading a different template file
 *  - title_parts( $parts ) - for changing the title
 *  - breadcrumbs( $trail ) - for changing the breadcrumbs
 *  - notices() - for displaying notices
 */
abstract class APP_View {

	/**
	 * Test if this class should handle the current view.
	 *
	 * Use is_*() conditional tags and get_query_var()
	 *
	 * @return bool
	 */
	abstract function condition();


	function __construct() {
		// 'init' hook (always ran)
		if ( method_exists( $this, 'init' ) )
			add_action( 'init', array( $this, 'init' ) );

		// $wp_query hooks
		$actions = array( 'parse_query', 'pre_get_posts' );
		$filters = array( 'posts_search', 'posts_clauses', 'posts_request', 'the_posts' );

		foreach ( $actions as $method ) {
			if ( method_exists( $this, $method ) )
				add_action( $method, array( $this, '_action' ) );
		}

		foreach ( $filters as $method ) {
			if ( method_exists( $this, $method ) )
				add_filter( $method, array( $this, '_filter' ), 10, 2 );
		}

		// other hooks
		add_action( 'template_redirect', array( $this, '_template_redirect' ) );
	}

	final function _action( $wp_query ) {
		if ( $wp_query->is_main_query() && $this->condition() ) {
			$method = current_filter();

//			debug( get_class( $this ) . '->' . $method . '()' );

			$this->$method( $wp_query );
		}
	}

	final function _filter( $value, $wp_query ) {
		if ( $wp_query->is_main_query() && $this->condition() ) {
			$method = current_filter();

//			debug( get_class( $this ) . '->' . $method . '()' );

			$value = $this->$method( $value, $wp_query );
		}

		return $value;
	}

	final function _template_redirect() {
		if ( !$this->condition() )
			return;

		if ( method_exists( $this, 'template_redirect' ) )
			$this->template_redirect();

		$filters = array(
			'template_include' => 'template_include',
			'appthemes_title_parts' => 'title_parts',
			'appthemes_notices' => 'notices',
			'breadcrumb_trail_items' => 'breadcrumbs',
		);

		foreach ( $filters as $filter => $method ) {
			if ( method_exists( $this, $method ) )
				add_filter( $filter, array( $this, $method ) );
		}
	}
}

Oh, got it. I'm too greedy when I want a class-for-all ;)