什么是Scala中所有函数的超类型？ [英] What is the supertype of all functions in Scala?

问题描述

我知道我可以对 Function1 或 Function2 执行 instanceOf $ c>等，但有没有一种通用的方式来看看是否有功能（它可以有任意数量的参数）。我尝试定义这样的内容：



  type FuncType =（Any *） - >任何
  

但是这也行不通。基本上我有一些代码如下所示：

  call =（name：Any，args：Any *） - >如果name.isFunction则name.castAs [Function] .apply（args）else name 
 aFunction =（name：String）=> Hello+名称
 notAFunction =Hello rick
 call（aFunction，rick）
 call（notAFunction）
  

解决方案

不，没有办法做到这一点，除了检查每个 Function1 ， Function2 等等。这些特质的父母都是 AnyRef 帮助你区别于其他任何东西。对于这些特征中的每一个，应用方法都会采用不同数量的参数，因此无法为它们提供具有apply方法的父项。最接近你想要做的是：
$ b $ pre $ def $ function def（function：AnyRef，args：Seq [任何]）：任何= {
函数匹配{
case f：Function1 [Any，Any] => f（args（0））
case f：Function2 [Any，Any，Any] => f（args（0），args（1））
//等等
}
}


但是这是疯狂而危险的，如果类型错误，它会在运行时抛出异常，例如

  arbitraryFunction（（x：Int）=> x * 2，List（I'm a String！））
  

I know I can do instanceOf checks against Function1 or Function2 etc but is there a generic way to see if something is function or not (it can have arbitray number of args). I tried defining something like this:

type FuncType = (Any*) -> Any

But that did not work either. Basically I have some code that looks like this:

call = (name: Any, args: Any*) -> if name.isFunction then name.castAs[Function].apply(args) else name
aFunction = (name: String) => "Hello " + name
notAFunction = "Hello rick"
call(aFunction, "rick")
call(notAFunction)

解决方案

No, there is no way to do this, except to go through and check each of Function1, Function2, etc. The parent of each of these traits is AnyRef, which won't help you to distinguish them from anything else. The apply method for each of these traits takes a different number of parameters, so there is no way to give them a parent that has an apply method. The closest you could probably get to what you are trying to do is:

def arbitraryFunction(function: AnyRef, args: Seq[Any]): Any = {
  function match {
    case f: Function1[Any, Any] => f(args(0))
    case f: Function2[Any, Any, Any] => f(args(0), args(1))
    // and so on
  }
}

But this is insane and dangerous and will throw exceptions at runtime if the types are wrong, e.g.

arbitraryFunction((x: Int) => x * 2, List("I'm a String!"))

这篇关于什么是Scala中所有函数的超类型？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！