make checkout field mandatory if

When creating your field make it non-required.

The ‘required’ check needs to be added custom so you can base it on another field. You’ll need to use one of the hooks triggered on validation for this, and add an error message if invalid.

Thanks for the answer Mike!
I made it non-required by default.

Any tips on where to look for the right hooks and how to do this?
or tips on how I might find this out myself.

thanks for the help!

https://github.com/woothemes/woocommerce/blob/master/includes/class-wc-checkout.php#L366

Thanks for the line Mike,

sorry for another question, but Im still stuck on how to progress with this.
I have no idea where to start creating a function that I can hook into do_action( 'woocommerce_before_checkout_process' );

can you create somekind of steplist so I can start working on what I need?

Thanks Mike!

Step 1: Code it ??

Sorry, I don’t and I think if I did, it would just be a snippet with the solution, no ??

Read up on actions here:

https://developer.www.ads-software.com/reference/functions/add_action/
https://www.nathanrice.net/blog/an-introduction-to-wordpress-action-hooks/
https://codex.www.ads-software.com/Plugin_API/Hooks

And you’ll want https://docs.woothemes.com/wc-apidocs/function-wc_add_notice.html to throw the error.