方法参数中多个连续的粗箭头在Scala中意味着什么? [英] What do multiple, consecutive fat arrows in method parameters mean in Scala?

问题描述

我了解一种方法可以具有如下代码:

I understand that a method can have code like this:

def m(p1:Int => Int) ...

这意味着该方法采用的函数p1返回一个Int

Which means this method takes a function p1 that returns an Int

但是在浏览Play时！框架代码我发现了一种难以理解的方法的特征:

But while browsing the Play! framework code i found a trait with indecipherable methods:

trait Secured {

  def username(request: RequestHeader) = request.session.get(Security.username)

  def onUnauthorized(request: RequestHeader) = Results.Redirect(routes.Auth.login)

  def withAuth(f: => String => Request[AnyContent] => Result) = {
    Security.Authenticated(username, onUnauthorized) { user =>
      Action(request => f(user)(request))
    }
  }

  /**
   * This method shows how you could wrap the withAuth method to also fetch your user
   * You will need to implement UserDAO.findOneByUsername
   */
  def withUser(f: User => Request[AnyContent] => Result) = withAuth { username => implicit request =>
    UserDAO.findOneByUsername(username).map { user =>
      f(user)(request)
    }.getOrElse(onUnauthorized(request))
  }
}

播放！ Scala安全性

f: User => Request[AnyContent] => Result是什么意思?乍一看，它看起来像一个返回请求类型为r的函数的方法. r然后返回Result.

What does the f: User => Request[AnyContent] => Result mean? At first glance it looks like a method that returns a function r of type Request; r then returns a Result.

这是正确的假设吗?

推荐答案

f:User => Request [AnyContent] =>结果是什么意思?乍一看，它看起来像一个返回Request类型的函数r的方法；然后r返回结果.

What does the f: User => Request[AnyContent] => Result mean? At first glance it looks like a method that returns a function r of type Request; r then returns a Result.

f返回类型为Request[AnyContent] => Result的函数，即采用Request[AnyContent]并返回Result的函数.

f returns a function of type Request[AnyContent] => Result, i.e. a function that takes a Request[AnyContent] and returns a Result.

换句话说，f是一个咖喱函数.您可以将其称为f(user)(request)以获取Result.

In other words f is a curried function. You could call it as f(user)(request) to get back a Result.

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