scala - spray marshalling cats.data.Xor -


i writing rest api using spray , having difficulties json marshalling. service returns cats.data.xor[failure, success]. how can return data type rest endpoint? how write response marshaller this?

the simplest solution call toeither on value in router, lets spray-provided either marshaller take over.

another solution provide own marshaller (i've done couple of times myself):

import cats.data.xor import spray.httpx.marshalling.toresponsemarshaller  implicit def xormarshaller[a, b](implicit   ma: toresponsemarshaller[a],   mb: toresponsemarshaller[b] ): toresponsemarshaller[xor[a, b]] =   toresponsemarshaller[xor[a, b]] { (value, ctx) =>     value match {       case xor.left(a)  => ma(a, ctx)       case xor.right(b) => mb(b, ctx)     }   }

this lets avoid both runtime cost (probably negligible) , syntactic cost (less negligible) of converting.

note cats removing xor in favor of standard library's either in upcoming versions, though, going toeither may practical solution.


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