Middleware Thunk

After careful consideration, decided not to add Middleware or Thunk to the library.

Because it just adds unnecessary layer, as SwiftUI maintains State separately, no need to dispatch Command asynchronously and then reduce on the root State like redux.js.

For example, when fetch feeds it can simply make async call directly on FeedListState, and then FeedListState reacts to completion which contains data or error.

Below is the experiment code I wrote for Thunk Middleware:

ThunkMiddleware.swift,

class ThunkMiddleware: Subscriber {
  
  public override func reduce(action: ReduxActionProtocol) {
    switch action {
    case let command as FetchFeedsCommand:
      Services.shared.fetchFeeds(endPoint: command.endPoint) { feeds in
        dispatch(action: FetchFeedsResultAction(feeds: feeds, error: nil))
      }
      break
    default:
      break
    }
  }
  
}

dispatch(action: FetchFeedsCommand(endPoint: Self.feedEndpoint))

On FeedListState,

  public override func reduce(action: ReduxActionProtocol) {    
    switch action {
    case let fetchFeedsResultAction as FetchFeedsResultAction:
      guard let feeds = fetchFeedsResultAction.feeds else {
        assertionFailure("Failed to fetch feeds. Error - \(fetchFeedsResultAction.error).")
        return
      }
      self.feeds = feeds
      break
    default:
      feeds = feeds.map { $0.reduce(action: action) }
    }  
  }