Question

说，我有以下内容：

trait SomeTrait {
  def someMethod: String;
}

object SomeObject extends SomeTrait {
  def someMethod = "something";
}

我想使用反射调用“someMethod”，因为我将对象名称作为String。类似的东西：

val objectName = "SomeObject"  
val someTrait:SomeTrait = ???.asInstanceOf[SomeTrait]  
someTrait.someMethod

或类似的东西。

由于

Answer 1

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

Answer 2

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

Answer 3

对于类，可以使用标准的java反射classOf方法轻松完成。对于Scala对象，它需要更多工作，但仍可以完成：


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

如何使用反射调用Scala Object方法？

3 个答案: