Is there a way to simplify Swift combine types?

Question

I have a custom Publisher that takes in a String key and emits values when data for that key changes. Say it's called MyCustomPublisher.

I have a function that I want to take in an instance of MyCustomPublisher, transform the value into a different key, and then create a separate instance of MyCustomPublisher. This looks like this:

    let myInfoProvider: MyCustomPublisher = ...
    myInfoProvider.tryMap { v -> Database in
        guard let value = v else { throw "No value provided" }
        return value
    }
    .map { v in
        MyCustomPublisher(key: v)
    }
    .switchToLatest()
    .tryMap { v -> String in
        guard let value = v else {
            throw "No value found"
        }
        
        return value
    }

Given that the data is a String, I would like the output type to be AnyPublisher<String, Error>, but the actual type reported by Swift is Publishers.TryMap<Publishers.SwitchToLatest<MyCustomPublisher, Publishers.TryMap<MyCustomPublisher, MyCustomPublisher>>, String>. How can I make this conform to AnyPublisher<String, Error>?

Answer 1

You would just call eraseToAnyPublisher() on the result.