Cash Stocks App

by Yariv Nissim

Architecture

This is a simple project using MVC. For anything bigger I would use MVVM. I've used VIPER before but it felt too verbose.

MVC is nice to for simple screens but to avoid a Massive View Controller I broke the functionality into smaller controllers and components (Network, API, a few enums). We could break if even further by extending the State object to handle table view data source functions, having an extension on the API to return a State object, and eventually if we want full sepration switch to MVVM so the VM handles most of this functionality and the VC is just a simple view. This would also make the businless logic testable separately from the View layer.

UI

I focused mostly on archiecture so the UI is pretty simple using a TableView and reusable cells. There's support for pull-to-refresh and to change the API source to simulate empty and malformed responses using a menu. The app supports dark mode and dynamic text sizes.

Model

Stock.swift file contains a Codable version of Stock with an extension to format some of the data.

View / ViewController

• StocksViewController.swift uses the StocksAPI class to load data and present it on screen. It has a State enum to represent the various states based on the API response - default, empty and malformed.
• There's also a helper enum APISource to simluate different responses which we would usually not have in a production project (or maybe hiding in an internal test screen)

Controller(s)

• NetworkController is a generic protocol to perform GET requests from a url endpoint and decode the returned JSON.

• It has as concrete implementation NetworkControllerImpl to perform actual network calls and a mock implementation MockNetworkController for unit test purposes

• StocksAPI is a protocol that represent the various API calls the app can perform.

• It takes a NetworkController using Dependency Injection so it can be unit tested, see StockAPITests.

• It has a few concrete implementations:

  • StocksAPIImpl uses the standard url that returns a valid response
  • StocksAPIEmptyImpl and StocksAPIMalformedImpl use other urls to simulate the other responses.

Trade offs

• I was using the Storyboard from the project template to save some time. We would probably set up the view controller in code and use the initializer to inject the StockAPI.
• I created multiple implementations of StocksAPI to keep the original protocol clean but another way could be to pass the url to the function or inject via init so that we could keep only a single concrete class.
• The NumberFormatter inside Stock.swift is not thread-safe. It would probably need to be accessed via a DispatchQueue.sync as a possible solution.

3rd Party Libraries

None.

How to run the project

Hit ⌘+R