Having this setup, trying to aggregate all to one ...

# arrow

[rcd27]

Having this setup, trying to aggregate all to one list only those who have AddressContactInfo. What is a better FP way to do that?

[rcd27]

However, seems legit, but maybe there is an existing tool for such kind of tasks.

[rcd27]

And yea, this is CastException 😄

[Lukasz Kalnik]

You could just use `filter`:

filter { it.contactInfo.isRight || it.contactInfo.isBoth }

[Lukasz Kalnik]

Using fold in your example you have basically reimplemented filter 😉

[Lukasz Kalnik]

BTW wouldn't it be better domain modeling to just use nullable or Option types for address/email contact info in the Contact data class? Ior is right-biased, which means AddressContactInfo is privileged over EmailContactInfo.
Or is it just an abstract example?

[simon.vergauwen]

Hey @rcd27,

Looks like you might be able use the ior binding for this.

ior(semigroup) {
  listOf(
    contactWithAddres,
    contactWithMail
   ).map { it.contactInfo.bind() }
  }
}

[simon.vergauwen]

Where isLeft short-circuits like Either.Left but isBoth accumulates the E and return` Right`

[simon.vergauwen]

isRight behaves just like Either.Right

[rcd27]

@Lukasz Kalnik the idea of picking Ior was that it represent either left, or right, or both. And I still don't know how to model that by hands, Nullability of those two values means that there is a 4th case: both missing, which is not valid for this case.

[rcd27]

Yeah, thanks @simon.vergauwen and @Lukasz Kalnik, I think Ior is not the best solution for my example, as it is right-biased, which is something I don't need.

[Lukasz Kalnik]

Ah, that's a very interesting case. So you need a guarantee that at least one of them is present. What about NonEmptyList?