We provide, discount and coupon code on our store powered by cartthrob. Its seems, if someone coupon code works too on discounted products but we don't want user to apply coupon code on discounted products. Is there anything built in cartthrob so, we can prevent user to apply coupon code on discounted items? or do we've to alter cartthrob code? I found similar question here - (In Cartthrob, how could one stop a discount being applied with any other coupon?) but that couldn't fulfil my need. Thanks
I'd guess you'd need to build an Extension to handle this since it's so specific to your needs.
CartThrob has their list of hooks here:
Looks like using the "cartthrob_calculate_discount" hook is your best bet. That's where I'd start at least.
This SE question will lists a number of addon development resources: https://expressionengine.stackexchange.com/a/15168/28
I built by first couple of extensions last month and the first was challenging but the next couple were less challenging. I took an existing Expresso Store extension and broke that down to create mine which helped a ton.