将 Scala 类作为参数传递? [英] Passing Scala Class as parameter?

问题描述

我希望将类作为参数传递给 Scala 函数，如下所示:

I'm looking to pass a Class as a parameter to a Scala function like so:

def sampleFunc (c : Class) : List[Any]  

(附带问题:参数中的类型应该是 Class 还是 Class[_]?)

(Side question: should the type in the parameter be Class or Class[_]?)

我传递 Class 类型的原因是为了检查对象是否属于特定类型.目前，作为一种解决方法，我将一个示例对象传递给该方法并比较两个对象的 .getClass 结果.我几乎不认为这是理想的，而且我确信在 Scala 中有一种明确定义的传递类型的方法.

The reason I'm passing a Class type is to check whether an object belongs to a particular type or not. At the moment, as a workaround, I'm passing a sample object to the method and comparing the two object's .getClass result. I hardly think this is ideal though and I'm sure there's a clearly defined way of passing Types in Scala.

推荐答案

好吧，对于您最初的问题:是的，您可以将 Scala 类作为参数传递.由于 Class 是一个类型构造器，它需要一个具体的类型来创建一个类型以用于参数.您可以像以前一样使用通配符存在类型 Class[_].

Well, to your original question: Yes, you can pass Scala Class as an argument. As Class is a type constructor, it needs a concrete type to make a type to be used in argument. You can use the wildcard existential type Class[_] as you have done.

def sample(c: Class[_]) = println("Get a class")
sample(classOf[Int])

但是，如果你想检查一个对象是否是某种类型，我建议你使用=:=，结合默认参数

However, if you want to check whether an object is of certain type, I recommend you to use =:=, in combination with default parameter

def checkType[T](obj: T)(implict ev: T =:= Int = null) =
  if (ev == null) "get other"
  else "get int"
checkType(123) // get int
checkType("123") // get other

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