How to consume the result object of Either in Use Case Layer?

[crjacinro]

So there is a repository layer and a user case layer. My use case calls the repository method (which returns either left or right and returns the User object as output when right.

[crjacinro]

Hi. Any ideas?

[crjacinro]

Not sure if this is correct but I can get it through result.either call and provide left or right callbacks, in which in the right callback, I can receive the User param.

[Zhuinden]

Have you tried .fold()?

[crjacinro]

Have you tried .fold()?

Nope, that method is not available in either.

[ferdyrod]

You could use .flatMap(). it gives access to the Right object.

result.flatMap() { it -> repository.saveUser(it) }

[Zhuinden]

Hmm according to Arrow's Either implementation, there should be a fold method.

  inline fun <R> fold(ifLeft: (LEFT) -> R, ifRight: (RIGHT) -> R): R = when (this) {
    is Right -> ifRight(right)
    is Left -> ifLeft(left)
  }

[ferdyrod]

Hmm according to Arrow's Either implementation, there should be a fold method.

Yes, Arrow's implementation does have fold method. But this project has a custom Either, it doesn't have all of Arrow methods. It only has flatmap() and map().

[Zhuinden]

Well it's kinda neutered if it cannot fold. That's kinda the whole point of either 😄

[crjacinro]

You could use .flatMap(). it gives access to the Right object.

result.flatMap() { it -> repository.saveUser(it) }

Thanks for this but doesn't flatmap transform data (instead of accessing object only) ? what is the impact of the flatmap operation to the original result variable?

[crjacinro]

Also upon checking the code, what is the difference between map and flat map?

[Zhuinden]

flatMap expects some kind of Either<L, R> while map in case of Either most likely means mapRight which expects some kind of R.