Payment Gateway

1. In Developer Studio , Create a Datatype Product Details and three properties product id, product name and Cost.
2. Configure the datatype and mark product id as the key value.
3. Create a casetype,in the first step add a data reference select products and reference it to product details.
4. In the second step add the data reference propety as read only.
5. Create an account in instamojo and copy the default payment link.

6.  Now ,create a property, payment link in the casetype's data model.
7.  Mark payment link as calculated read only.
8. Open the declare expression of payment link and paste the link and add
    eg: (""+.selectproducts.cost)