Scala:从字段名称反射设置字段值 [英] Scala: set a field value reflectively from field name

问题描述

我正在学习 Scala，但不知道如何做到这一点:

I'm learning scala and can't find out how to do this:

我正在 scala 对象和 google appengine 实体之间做一个映射器，所以如果我有一个这样的类:

I'm doing a mapper between scala objects and google appengine entities, so if i have a class like this:

class Student {
    var id:Long
    var name:String
}

我需要创建该类的一个实例，在java中我会通过它的名字来获取字段，然后执行 field.set(object, value) 但我找不到怎么做所以在 Scala 中.

I need to create an instance of that class, in java i would get the Field by it's name and then do field.set(object, value) but I can't find how to do so in scala.

我不能使用 Java 反射，因为 Student 的字段被视为私有字段，因此 field.set 会抛出错误.

I can't use java reflection since the fields of Student are seen as private and field.set throws an error because of that.

谢谢

推荐答案

Scala 将var"变成了一个私有字段，一个 getter 和一个 setter.因此，为了通过使用字符串识别 var 来获取/设置 var，您需要使用 Java 反射来查找 getter/setter 方法.下面是执行此操作的代码片段.请注意，此代码在 Scala 2.8.0 下运行，不存在重复方法名称和错误的处理.

Scala turns "var" into a private field, one getter and one setter. So in order to get/set a var by identifying it using a String, you need to use Java reflection to find the getter/setter methods. Below is a code snippet that does that. Please note this code runs under Scala 2.8.0 and handlings of duplicated method names and errors are nonexistent.

class Student {
  var id: Long = _
  var name: String = _
}

implicit def reflector(ref: AnyRef) = new {
  def getV(name: String): Any = ref.getClass.getMethods.find(_.getName == name).get.invoke(ref)
  def setV(name: String, value: Any): Unit = ref.getClass.getMethods.find(_.getName == name + "_$eq").get.invoke(ref, value.asInstanceOf[AnyRef])
}

val s = new Student
s.setV("name", "Walter")
println(s.getV("name"))  // prints "Walter"
s.setV("id", 1234)
println(s.getV("id"))    // prints "1234"

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