[英]Scala, cats, http4s - does not recognize <+> symbol from Http4s
我创建了两个Http4s
路由:
class FirstRoutes[F[_] : Async](service: FirstService[F]) extends Http4sDsl[F] {
def routes: HttpRoutes[F] = HttpRoutes.of[F] {
//... some code
}
}
class SecondRoutes[F[_] : Async] extends Http4sDsl[F] {
def routes: HttpRoutes[F] = HttpRoutes.of[F] {
//... some code
}
}
现在在我的main
方法中,我想这样调用这条路线:
override def run(args: List[String]): IO[ExitCode] =
for {
_ <- {
val app = {
//...
val firstRoutes = new FirstRoutes[F](someService)
val secondRoutes = new SecondRoutes[F]
(firstRoutes.routes <+> secondRoutes.routes).orNotFound
}
但是当我编译这段代码时,我得到了一个错误:
Error:(26, 33) value <+> is not a member of org.http4s.HttpRoutes[Server.F]
(firstRoutes.routes <+> secondRoutes.routes).orNotFound
这对我来说很奇怪,因为当我在路由类上使用 ctrl+space 并且我有很好的导入时,我通常可以使用这个<+>
符号:
import cats.effect._
import cats.data._
import org.http4s.server.blaze.BlazeServerBuilder
import cats.effect._
import cats.implicits._
找不到如何解决此问题并使用<+>
调用路由类。 也许这是intellij问题? 有人能帮我吗?
为 build.sbt 添加这个 scala 选项
scalacOptions += "-Ypartial-unification"
也许你应该阅读http://eed3si9n.com/herding-cats/import-guide.html
https://blog.softwaremill.com/9-tips-about-using-cats-in-scala-you-might-want-to-know-e1bafd365f88建议 2)
<+>
来自cats.syntax.semigroupk._
。
下面的代码编译
import cats.effect.{Async, ExitCode, IO}
import cats.syntax.semigroupk._
import org.http4s.HttpRoutes
import org.http4s.dsl.Http4sDsl
import org.http4s.syntax.kleisli._
import scala.language.higherKinds
class App {
class FirstRoutes[F[_] : Async](service: FirstService[F]) extends Http4sDsl[F] {
def routes: HttpRoutes[F] = HttpRoutes.of[F] {
???
}
}
class SecondRoutes[F[_] : Async] extends Http4sDsl[F] {
def routes: HttpRoutes[F] = HttpRoutes.of[F] {
???
}
}
trait FirstService[F[_]]
/*override*/ def run[F[_]: Async](args: List[String]): IO[ExitCode] = {
val someService: FirstService[F] = ???
for {
_ <- {
val app = {
//...
val firstRoutes = new FirstRoutes[F](someService)
val secondRoutes = new SecondRoutes[F]
(firstRoutes.routes <+> secondRoutes.routes).orNotFound
}
IO(???)
}
} yield ExitCode(1)
}
}
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