scalaz.io：扁平化IO [Throwable，Seq [IO [Nothing，String]]]

Question

I have IO[Throwable, Seq[IO[Nothing, String]]] and I would like to turn it into IO[Throwable, Seq[String]] . Any idea how ? I tried with flatten but I get weird implicit missing errors.

No implicits found for parameter asTraversable: IO[Nothing, Step] => GenTraversableOnce[B_]

Thank you !

Answer 1

I found the solution:

val data1: IO[Throwable, Seq[IO[Nothing, String]]]
val data2: IO[Throwable, IO[Nothing, Seq[String]]] = data1.map(IO.sequence)
val data3: IO[Throwable, Seq[String]] = data2.flatten

To do it in one step:

data1.flatMap(IO.sequence)

Courtesy of @andrey-tyukin