问题描述
我有一个接受函数的类
case class FunctionParser1Arg[T, U](func:(T => U))
def testFunc(name1:String):String = name1
val res = FunctionParser1Arg(testFunc)
我想从case类里面知道函数的类型签名信息.我想知道参数名称和类型.我已经成功地使用运行时镜像对象找到了类型,但没有找到名称.有什么建议吗?
I would like to know the type signature information on the function from inside the case class. I want to know both the parameter name and type. I have had success in finding the type using the runtime mirror objects, but not the name. Any suggestions?
推荐答案
好吧,假设你得到了 func
指向的实例的符号:
Ok, let's say you got the symbol for the instance func
points to:
import scala.reflect.runtime.universe._
import scala.reflect.runtime.{currentMirror => m}
val im = m reflect res.func // Instance Mirror
您可以从其类型成员中获取 apply
方法:
You can get the apply
method from its type members:
val apply = newTermName("apply")
val applySymbol = im.symbol.typeSignature member apply
既然我们知道它是一个方法,那就让它成为一个方法符号:
And since we know it's a method, make it a method symbol:
val applyMethod = applySymbol.asMethod
通过paramss
可以找到它的参数,我们知道一个参数列表中只有一个参数,所以我们可以得到第一个参数列表的第一个参数:
It's parameters can be found through paramss
, and we know there's only one parameter on one parameter list, so we can get the first parameter of the first parameter list:
val param = applyMethod.paramss(0)(0)
那么你要的是:
val name = param.name.decoded // if you want "+" instead of "$plus", for example
val type = param.typeSignature
您可能认为这是错误的答案,因为您得到的是 x$1
而不是 name1
,但是传递给构造函数的 不是命名函数 testFunc
,而是一个匿名函数,表示通过称为eta 扩展 的过程创建的方法.你找不到方法的参数名,因为你不能pass这个方法.
It's possible that you think that's the wrong answer because you got x$1
instead of name1
, but what is passed to the constructor is not the named function testFunc
, but, instead, an anonymous function representing that method created through a process called eta expansion. You can't find out the parameter name of the method because you can't pass the method.
如果这就是您的需要,我建议您改用宏.使用宏,您将能够准确查看编译时传递的内容并从中获取名称.
If that's what you need, I suggest you use a macro instead. With a macro, you'll be able to see exactly what is being passed at compile time and get the name from it.
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