Programmatically override the Custom Fields for a SearchWP engine

functions.php

<?php

class SwpProgrammaticCustomFields {

	// These meta keys will be indexed and made searchable
	private $meta_keys = array(
		array(
			'post_type' => 'post',
			'meta_keys' => array(
				array(
					'metakey' => 'my_meta_key',
					'weight' => 10,
				),
				array(
					'metakey' => 'another_meta_key',
					'weight' => 40,
				),
			),
		),
	);

	function __construct() {
		add_filter( 'searchwp_omit_meta_key', array( $this, 'whitelist_meta_key' ), 10, 3 );
		add_filter( 'searchwp_engine_settings_default', array( $this, 'modify_engine_settings' ), 10, 2 );
	}

	/*
	 * Retrieves meta keys from $this->meta_keys based on post type
	 */
	function get_meta_keys_for_post_type( $post_type = 'post' ) {
		if ( ! post_type_exists( $post_type ) ) {
			return array();
		}

		$meta_keys = array();

		foreach ( $this->meta_keys as $meta_keys ) {

			if ( $post_type !== $meta_keys['post_type'] ) {
				continue;
			}

			$meta_keys = wp_list_pluck( $meta_keys, 'metakey' );

			break;
		}

		return $meta_keys;
	}

	/**
	 * Tell SearchWP to index our meta keys
	 */
	function whitelist_meta_key( $excluded, $meta_key, $post_being_indexed ) {
		return ! in_array( $meta_key, $this->get_meta_keys_for_post_type( $post_being_indexed->post_type ) );
	}

	/*
	 * Replace engine Custom Fields with our $meta_keys
	 */
	function modify_engine_settings( $settings, $query ) {
		foreach ( $this->meta_keys as $meta_keys ) {
			if ( ! isset( $settings[ $meta_keys['post_type'] ]['weights'] ) ) {
				continue;
			}

			$settings[ $meta_keys['post_type'] ]['weights']['cf'] = $meta_keys['meta_keys'];
		}

		return $settings;
	}
}

new SwpProgrammaticCustomFields();