我怎样才能找到一个隐含的来自Scala的地方?
有没有办法问Scala编译器来告诉我,在程序中给定的点使用的规定隐含宣布?
如果没有,是否有一个算法,我可以手动跟踪找出自己在隐式声明的位置?
长的问题:
我下面简单的喷污物tutorial。
在下面的代码段(即将该this回购本教程):
pathEnd {
post {
entity(as[Question]) { question =>
completeWithLocationHeader(
resourceId = questionService.createQuestion(question),
ifDefinedStatus = 201, ifEmptyStatus = 409)
}
}
} ~
as
采用隐式FromRequestUnmarshaller[T]
型的(完整的源here):
def as[T](implicit um: FromRequestUnmarshaller[T]) = um
,当我问IntelliJ在哪里隐含来自(使用CMD + SHIFT + P),我得到:
当我跟随第一hint我得到这个:
trait UnmarshallerLifting {
implicit def fromRequestUnmarshaller[T](implicit um: FromMessageUnmarshaller[T]): FromRequestUnmarshaller[T] =
new FromRequestUnmarshaller[T] {
def apply(request: HttpRequest): Deserialized[T] = um(request)
}
...
这并不能帮助我找出其中隐含FromRequestUnmarshaller[T]
来自因为我想不通性状UnmarshallerLifting
如何混合到QuestionResource
如果我检查类层次:
我检查那个样子,他们可能含有这种内隐特质,例如this特质,但它不包含隐式:
trait MarshallingDirectives {
import BasicDirectives._
import MiscDirectives._
import RouteDirectives._
/**
* Unmarshalls the requests entity to the given type passes it to its inner Route.
* If there is a problem with unmarshalling the request is rejected with the [[spray.routing.Rejection]]
* produced by the unmarshaller.
*/
def entity[T](um: FromRequestUnmarshaller[T]): Directive1[T] =
extract(_.request.as(um)).flatMap[T :: HNil] {
case Right(value) ⇒ provide(value)
case Left(ContentExpected) ⇒ reject(RequestEntityExpectedRejection)
case Left(UnsupportedContentType(supported)) ⇒ reject(UnsupportedRequestContentTypeRejection(supported))
case Left(MalformedContent(errorMsg, cause)) ⇒ reject(MalformedRequestContentRejection(errorMsg, cause))
} & cancelAllRejections(ofTypes(RequestEntityExpectedRejection.getClass, classOf[UnsupportedRequestContentTypeRejection]))
/**
* Returns the in-scope FromRequestUnmarshaller for the given type.
*/
def as[T](implicit um: FromRequestUnmarshaller[T]) = um
/**
* Uses the marshaller for the given type to produce a completion function that is passed to its inner route.
* You can use it do decouple marshaller resolution from request completion.
*/
def produce[T](marshaller: ToResponseMarshaller[T]): Directive[(T ⇒ Unit) :: HNil] =
extract { ctx ⇒ (value: T) ⇒ ctx.complete(value)(marshaller) } & cancelAllRejections(ofType[UnacceptedResponseContentTypeRejection])
/**
* Returns the in-scope Marshaller for the given type.
*/
def instanceOf[T](implicit m: ToResponseMarshaller[T]) = m
/**
* Completes the request using the given function. The input to the function is produced with the in-scope
* entity unmarshaller and the result value of the function is marshalled with the in-scope marshaller.
*/
def handleWith[A, B](f: A ⇒ B)(implicit um: FromRequestUnmarshaller[A], m: ToResponseMarshaller[B]): Route =
entity(um) { a ⇒ RouteDirectives.complete(f(a)) }
}
object MarshallingDirectives extends MarshallingDirectives
看了20个不同的地方后,我变得沮丧。
有没有办法让scala编译器告诉我在一个程序中的某个给定点(在这个例子中是here)声明的某个隐式(在这个例子中是FromRequestUnmarshaller[T]
)在哪里?
如果没有,是否有一个算法,我可以手动跟踪找出自己在隐式声明的位置?
我在Google/SOF上找了这个问题,但是我发现的提示没有帮助。我也经历了this,我仍然不知道FromRequestUnmarshaller[T]
来自哪里。
通常我在编译器中启用-Xlog-implicits
以查看蕴含情况。
此外喷雾也被弃用,以支持akka-http。我建议切换。
我试过了,它不会告诉我隐式来自哪里,它只会抱怨被试过但不工作的隐含:( – jhegedus
我这样做(在迈克尔的意见建议):
import scala.reflect.runtime.universe.reify
println(reify(entity(as[Question])))
印刷:
Expr[spray.routing.Directive1[spray_examples.plain_rest.danielasfregola.quiz.management.entities.Question]](QuestionResource.entity(QuestionResource.as[Question](Deserializer.fromRequestUnmarshaller(Deserializer.fromMessageUnmarshaller(QuestionResource.json4sUnmarshaller(ManifestFactory.classType(classOf[spray_examples.plain_rest.danielasfregola.quiz.management.entities.Question])))))))
这直接告诉其中隐含的是来自:Deserializer.fromRequestUnmarshaller
而且,在这里是另一种方式,通过使用InteliJ的搜索使用功能:
也许您在寻找:http://*.com/questions/34903520/figuring-out-chain-of-implicit-invocations/34903876#34903876? –
很好,谢谢,我有一个看看。 – jhegedus