我有兩個DSL - EmployeeAction
和ContactAction
。這裏是我的特質(操作)使用免費Monad與任一
完整的要點是:link
sealed trait EmployeeAction[R]
case class GetEmployee(id: Long) extends EmployeeAction[Either[Error, Employee]]
sealed trait ContactAction[R]
case class GetAddress(empId: Long) extends ContactAction[Either[Error, Address]]
我用cats
「Coproduct
和Inject
這裏是我的計劃,讓經理地址:
type Program = Coproduct[EmployeeAction, ContactAction, A]
def findManagerAddress(employeeId: Long)
(implicit EA: EmployeeActions[Program],
CA: ContactActions[Program]): Free[Program, Address] = {
import EA._, CA._
for {
employee <- getEmployee(employeeId)
managerAddress <- getAddress(employee.managerId)
} yield managerAddress
}
以上沒有按不會編譯,因爲getEmployee
返回Either[Error, Employee]
。我如何處理Free
以便理解?
我試過用下面的EitherT
monad變換器,它在IntelliJ中沒有顯示錯誤,但是在構建時失敗。
for {
employee <- EitherT(getEmployee(employeeId))
managerAddress <- EitherT(getAddress(employee.managerId))
} yield managerAddress
下面是錯誤:
[scalac-2.11] /local/home/arjun/code/Free/src/FreeScalaScripts/src/free/program/Program.scala:71: error: no type parameters for method apply: (value: F[Either[A,B]])cats.data.EitherT[F,A,B] in object EitherT exist so that it can be applied to arguments (cats.free.Free[free.Program,Either[free.Error,free.Employee]])
[scalac-2.11] --- because ---
[scalac-2.11] argument expression's type is not compatible with formal parameter type;
[scalac-2.11] found : cats.free.Free[free.Program,Either[free.Error,free.Employee]]
[scalac-2.11] required: ?F[Either[?A,?B]]
[scalac-2.11] employee <- EitherT(getEmployee(employeeId))
[scalac-2.11] ^
如何應對無論是在理解和如何傳播錯誤給調用者?我想知道所有的員工ID是哪個呼叫失敗。
'EitherT'的編譯錯誤是什麼? –
@ZiyangLiu我在這個問題 – arjunswaj