如何确定"this"是类的实例还是对象的实例? [英] How to determine if `this` is an instance of a class or an object?

问题描述

假设我有一个抽象类的两个后代:

Suppose I have two descendants of an abstract class:

object Child1 extends MyAbstrClass {
    ...
}
class Child2 extends MyAbstrClass {
}

现在，我想确定(最好在MyAbstrClass的构造函数中)正在创建的实例是对象还是new创建的对象:

Now I'd like to determine (preferably in the constructor of MyAbstrClass) if the instance being created is an object or something created by new:

abstract class MyAbstrClass {
    {
        if (/* is this an object? */) {
            // do something
        } else {
            // no, a class instance, do something else
        }
    }
}

在Scala中有可能发生这种情况吗?我的想法是将所有从类派生到集合中的对象收集起来，但仅收集对象，而不收集由new创建的实例.

Is anything like that possible in Scala? My idea is to collect all objects that descend from a class into a collection, but only object, not instances created by new.

推荐答案

类似的东西:

package objonly

/** There's nothing like a downvote to make you not want to help out on SO. */
abstract class AbsFoo {
  println(s"I'm a ${getClass}")
  if (isObj) {
    println("Object")
  } else {
    println("Mere Instance")
  }
  def isObj: Boolean = isObjReflectively

  def isObjDirty = getClass.getName.endsWith("$")

  import scala.reflect.runtime.{ currentMirror => cm }
  def isObjReflectively = cm.reflect(this).symbol.isModuleClass
}

object Foo1 extends AbsFoo

class Foo2 extends AbsFoo

object Test extends App {
  val foob = new Foo2
  val fooz = new AbsFoo { }
  val f = Foo1
}

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