在applyOrElse Scala中缺少参数类型

Question

我有这段代码，我试图调用一个部分函数。当我构建我的项目时，我收到一个错误，指出missing parameter type ++ headerExtractor.applyOrElse(event, _ => Map.empty)。

我看过其他帖子，但我觉得这应该有效。我做错了什么？

我在这里调用标头提取器

private def publishToProfileExchange(customer: Schema.Customer, event: Schema.CustomerEvent): Future[Done] = {
val messageType: String = "ProfileEvent"
val headers: Map[String, AnyRef] = Map(
"profileId" -> customer.id.toString,
"eventType" -> event.eventType,
"type" -> messageType
) ++ headerExtractor.applyOrElse(event, _ => Map.empty)
...
//valid return values would be here
}
private val headerExtractor: PartialFunction[Schema.CustomerEvent, Map[String, AnyRef]] = {
case x if x.eventType.equalsIgnoreCase("message") && (x.eventData  "incoming").asOpt[Boolean].getOrElse(false) =>
Map("incomingMessage" -> "true")
}

Answer 1

您必须在.applyOrElse()上提供参数的类型。请参阅下面的示例

case class CustomerEvent(eventType: String, eventData: String)
val headerExtractor = new PartialFunction[CustomerEvent, Map[String, AnyRef]] {
def apply(x: CustomerEvent): Map[String, AnyRef] = Map("incomingMessage" -> "true")
def isDefinedAt(x: CustomerEvent): Boolean = x.eventType.equalsIgnoreCase("message")
}
assert(headerExtractor.applyOrElse(CustomerEvent("message", "{}"), (customerEvent: CustomerEvent) => Map.empty)
== Map("incomingMessage" -> "true"))
// or simply do (_: CustomerEvent)
assert(headerExtractor.applyOrElse(CustomerEvent("message", "{}"), (_: CustomerEvent) => Map.empty)
== Map("incomingMessage" -> "true"))

负面案例

assert(headerExtractor.applyOrElse(CustomerEvent("something-else", "{}"), (_: CustomerEvent) => Map.empty) 
== Map())