Composable Analytics

[oliverfoggin]

A while ago there were some discussions on Slack around how to approach analytics in a TCA app.

It could be done naively by just allowing each reducer to send analytics per action etc... and grabbing hold of a dependency to send it through etc...

But, I wanted a way that means...

1. I don't need to worry about mixing up production code with analytics code.
2. The production code and analytics are close enough together that it is still easy to see which analytics are being sent.
3. It is trivially easy to send analytics for any action and state.
4. It is trivially easy to exhaustively test analytics.
5. It is trivially easy to add multiple analytics providers (i.e. Firebase, DataDog, etc, etc...)

So, I came up with the idea of using an AnalyticsReducer to do all the work for you. The AnalyticsReducer is created with a trailing closure of the form (State, Action) -> AnalyticsData? so is very similar to the normal Reducer way of working except State is not inout so can't be mutated.

The short version of what it looks like to use it is something like this...

struct Feature: Reducer {
  struct State {
    var title: String
  }

  enum Action {
    case buttonTapped
  }

  var body: some ReducerOf<Self> {
    AnalyticsReducer { state, action in
      // state here is immutable so there is no way for your analytics to interfere with your app.
      switch action {
      case .buttonTapped:
        return  .event(name: "AppButtonTapped", properties: ["title": state.title])
      }
    }
  
    Reduce<State, Action> { state, action in
      // your normal app logic sits here unchanged
    }
  }
}

Anyway, I just put it on GitHub for anyone else to use... https://github.com/oliverfoggin/swift-composable-analytics

Any comments or contributions are welcome.

Thanks 😄