Comprehensive iOS Grocery-Shopping App

I need a comprehensive iOS application for grocery ordering. Essential features should include:

- User registration and login. This is a must for personalized user experiences.

- Product catalog with search functionality, so users can easily navigate through our extensive range of products.

- Shopping cart for easy ordering. This will ensure a smooth and user-friendly ordering experience.

Also, the application will require integration with a specific payment gateway. However, I'd prefer to discuss which payment gateway to integrate with after bid acceptance.

Ideal freelancers for this job should have prior experience in iOS development and building shopping apps. Integrating payment gateways is a critical skill as well. Looking forward to seeing your proposals!

This will require services and interfaces for both the customers, and the merchants. The milestones will include:

1. Architecture.

2. UX Design

3. Implementation

4. Cloud Deployment

5. App Store Deployment