WooCommerce: Change shipping class based on quantity in cart

Question

I'm having difficulty with the shipping classes in WooCommerce. It's a webshop containing products for mailbox and packages.

However, if the cart contains 3 or more "mailbox" products, then the shipping class should change to "package".

I've tried changing the code from this question: Change shipping class based on cart items shipping class count in Woocommerce , but I couldn't figure it out.

Can someone help me with this?

Answer 1

The problem could be that you change the slug naming in the code.
Just implemented this and works fine!

// HERE define your shipping class SLUG
$mailbox_shipping_class = 'your-mailbox-shipping-class-slug';