如何确定对象是否为值类类型,以便在以下示例中测试将打印 id 是 AnyVal?
class MyId(val underlying: Int) extends AnyVal
class AnyValSuite extends FunSuite {
class Sample {
def doIt[T](t: T)(implicit tag: TypeTag[T]): Unit = {
if(???) println(s"$t is an AnyVal")
}
}
test("Getting info if a type is a value class") {
new Sample().doIt(new MyId(1))
}
}
@senia:感谢您的回答。完美运行。是否也可以找出 Value 类包装的原始类型?
现在扩展示例:
class MyId(val underlying: Int) extends AnyVal
class NonAnyValId(val underlying: Int)
class AnyValSuite extends FunSuite {
class Sample {
def doIt[T](t: T)(implicit tag: TypeTag[T]): Unit = {
if(implicitly[TypeTag[T]].tpe <:< typeOf[AnyVal]) println(s"$t is an AnyVal")
else println(s"$t is not an AnyVal")
}
}
test("Getting info if a type is a value class") {
new Sample().doIt(new MyId(1))
new Sample().doIt(new NonAnyValId(1))
new Sample().doIt(1)
}
}
返回:
MyId@1 is an AnyVal
NonAnyValId@38de28d is not an AnyVal
1 is an AnyVal
编辑2: 现在包装类型检查:
import org.scalatest.FunSuite
import scala.reflect.runtime.universe._
class MyId(val underlying: Int) extends AnyVal
class NonAnyValId(val underlying: Int)
class AnyValSuite extends FunSuite {
class Sample {
def doIt[T](t: T)(implicit tag: TypeTag[T]): Unit = {
val tpe= implicitly[TypeTag[T]].tpe
if(tpe <:< typeOf[AnyVal]) {
println(s"$t is an AnyVal")
val fields = tpe.members.filter(! _.isMethod)
fields.size match {
case 0 => println("has no fields, so it's a primitive like Int")
case 1 => {
println("has a sole field, so it's a value class")
val soleValueClassField = fields.head.typeSignature
println("of type: " + soleValueClassField)
if(typeOf[Int] == soleValueClassField) println("It wraps a primitive Int")
}
case 2 => throw new Exception("should never get here")
}
}
else println(s"$t is not an AnyVal")
}
}
test("Getting info if a type is a value class") {
new Sample().doIt(new MyId(1))
println
new Sample().doIt(new NonAnyValId(1))
println
new Sample().doIt(1)
}
}
返回:
MyId@1 is an AnyVal
has a sole field, so it's a value class
of type: Int
It wraps a primitive Int
NonAnyValId@3d0d4f51 is not an AnyVal
1 is an AnyVal
has no fields, so it's a primitive like Int
只是想知道是否有一些更简单的解决方案?