在 Scala 中在运行时获取类型的字符串表示
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Getting the string representation of a type at runtime in Scala
提问by Kevin Albrecht
In Scala, is it possible to get the string representation of a type at runtime? I am trying to do something along these lines:
在 Scala 中，是否可以在运行时获取类型的字符串表示？我正在尝试按照以下方式做一些事情：
def printTheNameOfThisType[T]() = {
println(T.toString)
}
采纳答案by svrist
Note: this answer is out of date!
注意：此答案已过时！
Please see answer using TypeTag for Scala 2.10 and above
请参阅使用 TypeTag for Scala 2.10 及更高版本的答案
May I recommend #Scala on freenode
我可以在freenode上推荐#Scala吗
10:48 <seet_> http://stackoverflow.com/questions/190368/getting-the-string-representation-of-a-type-at-runtime-in-scala <-- isnt this posible?
10:48 <seet_> possible
10:48 <lambdabot> Title: Getting the string representation of a type at runtime in Scala - Stack Overflow,
http://tinyurl.com/53242l
10:49 <mapreduce> Types aren't objects.
10:49 <mapreduce> or values
10:49 <mapreduce> println(classOf[T]) should give you something, but probably not what you want.
回答by Julie
In Scala 2.10 and above, use TypeTag, which contains full type information. You'll need to include the scala-reflectlibrary in order to do this:
在 Scala 2.10 及更高版本中，使用TypeTag包含完整类型信息的 。您需要包含scala-reflect库才能执行此操作：
import scala.reflect.runtime.universe._
def printTheNameOfThisType[T: TypeTag]() = {
println(typeOf[T].toString)
}
You will get results like the following:
你会得到如下结果：
scala> printTheNameOfThisType[Int]
Int
scala> printTheNameOfThisType[String]
String
scala> printTheNameOfThisType[List[Int]]
scala.List[Int]
回答by Julie
There's a new, mostly-undocumented feature called "manifests" in Scala; it works like this:
Scala 中有一个新的、几乎没有记录的特性，称为“清单”；它是这样工作的：
object Foo {
def apply[T <: AnyRef](t: T)(implicit m: scala.reflect.Manifest[T]) = println("t was " + t.toString + " of class " + t.getClass.getName() + ", erased from " + m.erasure)
}
The AnyRef bound is just there to ensure the value has a .toString method.
AnyRef 边界只是为了确保该值具有 .toString 方法。
回答by svrist
Please note that this isn't really "the thing:"
请注意，这并不是真正的“事情”：
object Test {
def main (args : Array[String]) {
println(classOf[List[String]])
}
}
gives
给
$ scala Test
class scala.List
I think you can blame this on erasure
我想你可以把这归咎于擦除
====EDIT==== I've tried doing it with a method with a generic type parameter:
====编辑==== 我试过用一个带有泛型类型参数的方法来做到这一点：
object TestSv {
def main(args:Array[String]){
narf[String]
}
def narf[T](){
println(classOf[T])
}
}
And the compiler wont accept it. Types arn't classes is the explanation
编译器不会接受它。类型不是类是解释
