A simple chat app.

It is developed using SwiftUI, Combine and asynchronous swift API without extra dependencies.

Minimum iOS version is 15 due to use of asynchronous API.

The app uses simplified MVVM pattern.

• DataModel: defines DTO and fully generated from a json schema.
• Network: implementation of a network client. It performs basic network operations: retrieving list of messages and creating a new message.
• ViewModel: defines a view model, which provides necessary functionality for retrieving and sending messages using NetworkClient. It also contains data transformation logic (converts DTO into VO and vise versa).
• App: provides app UI and uses ViewModel for interacting with network. App listens to ViewModel changes and updates UI using Combine.

DataModel, ViewModel are covered with unit tests and use json samples as input data.

Nice to have, but not implemented:

• UI tests for testing basic app workflow (register, get messages, send a message). Should use a mock server.
• Network tests using a mock server.
• Snapshot tests to ensure UI consistency.

All these tests can be ran on a CI server, so testing will be fully automated. General approach is to use fastline

Manual testing is still desirable cause creation and maintenance of UI/integration tests is tough and doesn't guarantee that app doesn't have bugs. Also QA helps with problem reproduction.

Use of cutting edge technologies greatly simplifies app development, but also limits user audience. It might be critical for services whose customers use old devices (seniors, children, low income people). Minimum SwiftUI iOS version is 13, but we require 15 cause of async api. By using less convenient but fully functional URLSession we can lower OS requirements.

Current implementation uses a single ViewModel which will lead to oversized code. When app becomes more complex, it should be split into smaller and more specialized view models (e.g. message list model, message composition model, registration model, etc.). It will also reduce number of VOs.

Current implementation uses a single Xcode project for all UI. It would be better to define features in isolated libraries (contact list, message list, registration). It will improve testability, inter dependency visibility and reduce number of merging conflicts.

As team growth, there Xcode project conflicts become a problem. We can mitigate this problem by using SPM, so Xcode product will be modified much less. Alternatively we can consider use of bazel or buck which eliminates Xcode project completely. But it requires extra knowledge from developers.