[英]Scala get constructor parameters at runtime
I'm trying to use reflection to get the types of constructor parameters of a class at runtime. 我正在尝试使用反射在运行时获取类的构造函数参数的类型。 The method below is in the abstract superclass. 下面的方法在抽象超类中。 However this.type
is not behaving as expected. 但是, this.type
类型的行为不符合预期。 Any help would be much appreciated. 任何帮助将非常感激。
/**
* Maps constructor field names to types
*
* @return Map[String, Type]
*/
def getParamTypes: Map[String, ru.Type] =
ru.typeOf[this.type].
member(ru.termNames.CONSTRUCTOR)
.asMethod.paramLists(0).
foldRight(Map(): Map[String, ru.Type])((p, a) => {
a + (p.name.decodedName.toString -> p.typeSignature)
})
Method typeOf
requires implicit TypeTag
. 方法typeOf
需要隐式TypeTag
。 You should use TypeTag
directly to get type information available only on call-side: 您应该直接使用TypeTag
来获取仅在调用方可用的类型信息:
trait Test {
def getParamTypes(implicit ttag: ru.TypeTag[this.type]) =
ttag.tpe.
member(ru.termNames.CONSTRUCTOR).
asMethod.paramLists(0).
foldRight(Map(): Map[String, ru.Type])((p, a) => {
a + (p.name.decodedName.toString -> p.typeSignature)
})
}
class TestC(i: Int, s: String) extends Test
val t = new TestC(1, "")
t.getParamTypes
// Map[String,Type] = Map(s -> String, i -> Int)
Alternatively you could get Type
of this
from Class
. 或者,您可以从Class
获得this
Type
。
trait Test2 {
def getParamTypes: Map[String, ru.Type] = {
val clazz = getClass
val tpe = ru.runtimeMirror(clazz.getClassLoader).classSymbol(clazz).toType
tpe.
member(ru.termNames.CONSTRUCTOR).
asMethod.paramLists(0).
foldRight(Map(): Map[String, ru.Type])((p, a) => {
a + (p.name.decodedName.toString -> p.typeSignature)
})
}
}
class TestC2(i: Int, s: String) extends Test2
new TestC2(1, "").getParamTypes
// Map[String,Type] = Map(s -> String, i -> Int)
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