Scala玩動作組合：聲明ActionBuilder，通過組合幾個ActionFunction產生動作

Question

我試圖圍繞我的頭玩遊戲動作組合。我的主要參考：https://www.playframework.com/documentation/2.3.6/ScalaActionsComposition

這是我想要實現（要能這樣聲明函數在我的控制器）是什麼：

def sensitiveOperation() = Protected {request => ...} 

所以，我的行動計劃是：

/** 
* Now I need to make an Action builder that wraps two things: 
* UserAction (to make sure that request is transformed to UserRequest), 
* and then... an Action that checks if userId has a value (it proceeds by invoking the actual action) 
* , or otherwise return Unauthorized 
*/ 

所以...我有這三樣東西：

class UserRequest[A](val userId: Option[String], request: Request[A]) extends WrappedRequest[A](request) 

object UserAction extends ActionBuilder[UserRequest] with ActionTransformer[Request, UserRequest] { 
    def transform[A](request: Request[A]) = Future.successful { 
    new UserRequest(request.session.get("userId"), request) 
    } 
} 

object CheckUserId extends ActionFilter[UserRequest] { 
    def filter[A](userRequest: UserRequest[A]) = Future.successful { 
    userRequest.userId match { 
     case Some(userIdVal) => None 
     case None => Some(Results.Unauthorized("User is not logged in. Log in first.")) 
    } 
    } 
} 

所有這三樣東西編譯。

我的問題是：如何聲明一個使用UserAction和CheckUserId的操作？

object Protected extends ActionBuilder[Request] { 
    def invokeBlock[A](request: Request[A], block: (Request[A]) => Future[Result]) = { 
    block(request) 
    } 
    override def composeAction[A](action: Action[A]) = ... ?? how ?? .... 
} 

我試圖在這之下，但它給編譯錯誤：

override def composeAction[A](action: Action[A]) = UserAction andThen CheckUserId 

---

。附加

現在我可以解決它使用此：

def sensitiveOperation() = (UserAction andThen CheckUserId) {request => ...} 

但是，我仍然瘦ķ那將是更漂亮，如果我可以定義一個名爲「保護」，實際上做同樣的同伴對象（和-ING UserAction和CheckUserId）......，這樣我就可以用原來的想法回去：

def sensitiveOperation() = Protected {request => ...} 

如何實現它？

由於提前， 拉嘎

Answer 1

你不能用一個對象做到這一點，因爲對象不能是結果一種表達。但是，您可以將其設置爲def或val，並且您可以將其放入包裝對象中，例如：

package object security { 
    val Protected = UserAction andThen CheckUserId 
} 

Answer 2

我想我已經找到了如何....

object Protected extends ActionBuilder[UserRequest] { 
    def invokeBlock[A](request: Request[A], block: (UserRequest[A]) => Future[Result]) = { 
    (UserAction andThen CheckUserId).invokeBlock(request, block) 
    } 
}