is there an (idiomatic) way to do `if let Left(err) = myEitherValue { /* do something with err */ }`...

# arrow

[conner]

is there an (idiomatic) way to do if let Left(err) = myEitherValue { /* do something with err */ } ? basically i want to run a block if myEitherValue is Left, and i would like to avoid casting it

[conner]

basically this

fun <E, T> Either<E, T>.ifLeft(f: (E) -> Unit) = when(this) {
  is Either.Left<E> -> f(this.value)
  else -> Unit
}

but maybe this is built-in or there's a more idiomatic way? 🙂

[conner]

ah, i just read the above thread, and it sounds like tapLeft is what i want 🙂 (just need to upgrade to 1.x)

[Peter]

mapLeft?

[Peter]

Depends on what you want to do