Pseudo-elegant way to flush rewrite rules after creating a custom post type.

custom-post-type-flush-rewrite-rules.php

<?php
/**
 * Example for writing a WP plugin that adds a custom post type and flushes
 * rewrite rules only once on initialization.
 */

/**
 * On activation, we'll set an option called 'my_plugin_name_flush' to true,
 * so our plugin knows, on initialization, to flush the rewrite rules.
 */
function my_plugin_name_activation() {
    add_option('my_plugin_name_flush', 'true');
}

register_activation_hook( __FILE__, 'my_plugin_name_activation' );

/**
 * On deactivation, we'll remove our 'my_plugin_name_flush' option if it is
 * still around. It shouldn't be after we register our post type.
 */
function my_plugin_name_deactivation() {
    delete_option('my_plugin_name_flush');
}

register_deactivation_hook( __FILE__, 'my_plugin_name_deactivation' );

/**
 * Register our post type. Specifically, we'll check if our
 * 'my_plugin_name_flush' option is true. If so, we'll flush the rewrite rules,
 * then delete the option, so it only flushes the rules once.
 */
function my_plugin_name_register_post_types() {
    // Register code for your new post type here...
    // register_post_type( 'custom_post_type_name', $customPostTypeDefs );

    // Check the option we set on activation.
    if (get_option('my_plugin_name_flush') == 'true') {
        flush_rewrite_rules();
        delete_option('my_plugin_name_flush');
    }
}

add_action( 'init', 'my_plugin_name_register_post_types' );