因此,我尝试获取Scala对象类中每个字段的类型:
package myapp.model
object MyObject {
val theInt: Option[Int]
}
在这篇文章中使用了Brian提供的ReflectionHelper。我使用getFieldType
,但它返回Option[Object]
,而不是它本身,它是Option[Int]
。该答案中的示例代码适用于Case类,例如:
package myapp.model
case class Person(
name: String,
age: Option[Int]
)
scala> ReflectionHelper.getFieldType("myapp.model.Person", "age") // int
res12: Option[reflect.runtime.universe.Type] = Some(Option[Int])
但是,如果我在Scala对象字段上运行getFieldType
,我们会得到如下结果:
scala> ReflectionHelper.getFieldType("myapp.model.MyObject$", "theInt")
res10: Option[reflect.runtime.universe.Type] = Some(Option[Object])
导致这种行为的Scala对象有什么不同之处?如何才能让getFieldType
返回Option[Int]
,而不是像Case类那样返回Option[Object]
?
为了方便起见,下面是另一个问题中的ReflectionHelper:
import scala.reflect.runtime.{ universe => u }
import scala.reflect.runtime.universe._
object ReflectionHelper {
val classLoader = Thread.currentThread().getContextClassLoader
val mirror = u.runtimeMirror(classLoader)
def getFieldType(className: String, fieldName: String): Option[Type] = {
val classSymbol = mirror.staticClass(className)
for {
fieldSymbol <- classSymbol.selfType.members.collectFirst({
case s: Symbol if s.isPublic && s.name.decodedName.toString() == fieldName => s
})
} yield {
fieldSymbol.info.resultType
}
}
def maybeUnwrapFieldType[A](fieldType: Type)(implicit tag: TypeTag[A]): Option[Type] = {
if (fieldType.typeConstructor == tag.tpe.typeConstructor) {
fieldType.typeArgs.headOption
} else {
Option(fieldType)
}
}
def getFieldClass(className: String, fieldName: String): java.lang.Class[_] = {
// case normal field return its class
// case Option field return generic type of Option
val result = for {
fieldType <- getFieldType(className, fieldName)
unwrappedFieldType <- maybeUnwrapFieldType[Option[_]](fieldType)
} yield {
mirror.runtimeClass(unwrappedFieldType)
}
// Consider changing return type to: Option[Class[_]]
result.getOrElse(null)
}
}
1条答案
按热度按时间qhhrdooz1#
尝试