如何在钩子中访问WooCommerce自定义计费字段

Question

I'm writing a custom WordPress function that will change the flat_rate shipping when a customer changes the "State" field from a select menu. Currently I'm doing it in my theme's functions.php

I have created a custom field to represent "State" field as a drop down menu in the billing fields. I used "WooCommerce Checkout Manager" plugin to setup the custom field and disabled the default "State" field.

Now I want to change the shipping cost depending on the value of my custom "State" field. I'm unable to retrieve the data of the field. Also I want to know what hook I can use to change the flat rate shipping once this field's value is changed.

I've used this filter hook (woocommerce_package_rates) and it doesn't work.

Here is my code to do it which I got it from another tutorial then made my customization

function wc_ninja_change_flat_rates_cost( $rates, $package ) {
$destination = $package['destination'];
$city = $destination['myfield12']; // getting the city field value

// Make sure flat rate is available

if ( isset( $rates['flat_rate'] ) ) {

    if ( $city == 'Alex' || $city == 'الإسكندرية' ) {
        // Set flat rate to cost $10 more
        $rates['flat_rate']->cost = 30;
    }
    else {
        $rates['flat_rate']->cost = 20;
    }
}

return $rates;
}
add_filter( 'woocommerce_package_rates', 'wc_ninja_change_flat_rates_cost', 10, 2 );

Answer 1

I found this:

http://phpwpinfo.com/how-to-update-shipping-cost-in-cart-dynamically-based-on-a-custom-field-in-woocommerce/

Basically it captures the field data through JS and send an Ajax request to the server which then stores the value in the session. Then adds an additional fee. It is not exactly what I was seeking to do but its a functional workaround.