Scala-如何在foreach理解块中使用foreach循环? [英] Scala - how to use foreach loop in for comprehension block?
问题描述
我有一个简单的代码:
override def createContributorsList(url: String, params: String): F[List[Contributor]] = getContributorsFromClient(url, params).fold[List[Contributor]](_ => List(), res => res)
override def createReposList(organization: String, params: String): F[List[GitRepository]] = getReposFromClient(organization, params).fold[List[GitRepository]](_ => List(), res => res)
此代码从github返回存储库列表和贡献列表.但是现在我需要为createReposList
找到的每个存储库调用createContributorsList
.我已经完成了for comprehension
块:
This code return list of repositories from github and list of contributions. But now I need to call createContributorsList
for every repository I found by createReposList
. I have done a for comprehension
block:
val stats = new StatisticsRepository[IO](new GitHttpClient[IO])
val res = for {
repos <- stats.createReposList("github", "")
} yield repos
工作正常,它找到了给定组织(github)的存储库.所以我尝试这样做:
It works fine, it found repositories for given organization (github). So I tried do it like this:
val res = for {
repos <- stats.createReposList("github", "")
list = repos.foreach(repo => stats.createContributorsList(repo.contributors_url, ""))
} yield (repos, list)
但是list
始终为空.我不知道没有for comprehension
怎么办,因为我在Monads
上像IO
一样在这里进行操作.我应该如何创建代码来遍历repos
的每个回购并在所有人身上调用stats.createContributorsList
?
But list
is always empty. I don't know how I could do this without for comprehension
, because I operate here on Monads
like IO
. How I should create a code to loop over every repo from repos
and call stats.createContributorsList
on everyone?
推荐答案
尝试flatTraverse
import cats.syntax.flatMap._
import cats.syntax.functor._
import cats.syntax.traverse._
import cats.instances.list._
val res: F[(List[GitRepository], List[Contributor])] = for {
repos <- stats.createReposList("github", "")
list <- repos.flatTraverse(repo => stats.createContributorsList(repo.contributors_url, ""))
} yield (repos, list)
foreach
返回Unit
,所以这不是您所需要的.
foreach
return Unit
so that's not what you need.
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