如何使用反射调用 Scala 对象方法？
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How do I call a Scala Object method using reflection?
提问by sanjib
say, I have the following:
说，我有以下几点：
trait SomeTrait {
def someMethod: String;
}
object SomeObject extends SomeTrait {
def someMethod = "something";
}
I would like to call "someMethod" using reflection as I have the object name as a String. Something like:
我想使用反射调用“someMethod”，因为我将对象名称作为字符串。就像是：
val objectName = "SomeObject"
val someTrait:SomeTrait = ???.asInstanceOf[SomeTrait]
someTrait.someMethod
or something similar.
或类似的东西。
Thanks
谢谢
回答by Thomas Jung
def companion[T](name : String)(implicit man: Manifest[T]) : T =
Class.forName(name + "$").getField("MODULE$").get(man.erasure).asInstanceOf[T]
val result = companion[SomeTrait]("SomeObject").someMethod
回答by Ambling
Since scala 2.10, we can use the reflection of Module:
从scala 2.10开始，我们可以使用Module的反射：
import scala.reflect.runtime.universe
val runtimeMirror = universe.runtimeMirror(getClass.getClassLoader)
val module = runtimeMirror.staticModule("SomeObject")
val obj = runtimeMirror.reflectModule(module)
val someTrait:SomeTrait = obj.instance.asInstanceOf[SomeTrait]
someTrait.someMethod
回答by Arjan Blokzijl
For classes, this can be done pretty easily using the standard java reflection classOf method. For Scala objects, it is a bit more work, but it still can be done:
对于类，这可以使用标准的 java 反射 classOf 方法很容易地完成。对于 Scala 对象，它的工作有点多，但仍然可以做到：
trait SomeTrait { def someMethod: String}
object SomeObject extends SomeTrait { def someMethod = "something"}
class SomeClass extends SomeTrait { def someMethod = "something"}
object Main {
def main(args:Array[String]) = {
val someClassTrait:SomeTrait = Class.forName("SomeClass").newInstance().asInstanceOf[SomeTrait]
println("calling someClassTrait: " + someClassTrait.someMethod)
val objectName = "SomeObject$"
val cons = Class.forName(objectName).getDeclaredConstructors();
cons(0).setAccessible(true);
val someObjectTrait:SomeTrait = cons(0).newInstance().asInstanceOf[SomeTrait]
println("calling someObjectTrait: " + someObjectTrait.someMethod)
}
}
//prints:
calling someClassTrait: something
calling someObjectTrait: something
