Can you have an Effect return another Effect? i.e. Chain Effects together and pass one Output to another in the same Action?

Related Projects Swift Composable Architecture
1

I have a scenario where I have one Effect that returns an array of [String]. I then pass that to my Networking Effect which makes an API request and returns a Decodable Output, which is what I ultimately want to use to make a decision and return an Action. Is there a way to chain Effects together where you can use the Output of one Effect and pass it to another Effect, without needing to return an Action between the Effects?

2

If your effects are based on Combine publishers, then .flatMap operator is what you need to use. If your effects are based on async/await dependencies endpoints then just call them in Effect.run { send in } and send action in the end.

3

Unfortunately they are Async/Await based. Not possible using that?

4

If async/await then it depends it they are function or AsyncStream. If normal async function then try something it like this:

case .fetchItems:
  return .run { send in 
    let payload = await self.preparePayload()  // returns [String]
    let response = await self.apiClient.fetchFor(payload)  // returns Decodable Output
    send(.updateItems(response))
  }

If your endpoints are AsyncStreams, then await/reduce/map/flatMap them in .run { send in } as you need and in then use send(.action(finalDataReadyToBeSendToAction)).

When dealing with async/await endpoints then it's all like handling this as a normal swift concurrency in Effect.run.

1 Like
5

Great, that worked. Thank you!