How to get data from cart in my shopify app?

Shopify Discussion
1

Hello.
I am developing a shopify app for my client. What I’m trying to achieve is that:

  1. I want to show available shipping methods to the customer.

  2. When the customer selects the shipping method, I want to get the selection in my shopify app and also get all the cart items in my app as well.

  3. I would then process the item prices according to the shipping method and return the prices to my cart and the customer can then go to checkout with updated price.

I’m having trouble getting the user selection and item data in my shopify app. I have studied shopify checkout api as well as the related api’s documentation but i couldnt find any help there.

I would appreciate if someone can guide me in this.

Thank you.