cfwc_add_custom_field_item_data.php

/**
 * Add the text field as item data to the cart object
 * @since 1.0.0
 * @param Array 		$cart_item_data Cart item meta data.
 * @param Integer   $product_id     Product ID.
 * @param Integer   $variation_id   Variation ID.
 * @param Boolean  	$quantity   		Quantity
 */
function cfwc_add_custom_field_item_data( $cart_item_data, $product_id, $variation_id, $quantity ) {
	if( ! empty( $_POST['cfwc-title-field'] ) ) {
		// Add the item data
		$cart_item_data['title_field'] = $_POST['cfwc-title-field'];
	}
	return $cart_item_data;
}
add_filter( 'woocommerce_add_cart_item_data', 'cfwc_add_custom_field_item_data', 10, 4 );