Status

Design and development decisions

network layer is made of service provider and operations executor
- protocols allowed for mock implementation to be used during testing
- separation of both allows to implement custom network operations execution strategies if needed
- DefaultServicesProvider implements basics of HTTP communication. Should the server require custom headers or any other customisation a custom provider can be implemented.
use of IBDesignable for UI components; this allows for clean Interface Builder work, cleaner UI code and better separation views
due to the nature of the app the model objects are close to API hence they contain code for creating them from JSON. Would the model be internal to the app I would extract this code to JohnLewisModelBuilder to keep the model JSON agnostic.
Since prices are used for nothing but displaying in UI they are kept as strings. I the future, when improving the app, it would be worth to have a designated "Price" model object and "PriceFormatter" class which would format the price according to the value and currency code
ApplicationConfiguration is created in Interface Builder and injected into ProductsGridViewController. This is good enough for this exercise. In long term there would be an entity responsible for creating and providing the configuration, i.e. initial screen downloading additional settings from server.

basic network error handling
no advanced network operations queueing
in-memory data caching; can be improved by using filesystem and if ETag header would be sent by server
on product details page status the UI is at bare minimum; photos carousel is not implemented due to limited time