reflection - Getting public fields (and their respective values) of an Instance in Scala/Java

Question

PHP introduces a method that allows you to pick out all public values of an instance. Is there any way to do this in Scala? That is to fetch all values of all public fields of an instantiated class (not object).

Let's us assume I have this class

class TestElement( datatype: Datatype, var subject: String, var day: Int, var time: Int )
  extends DataElement( datatype: Datatype ) {    
   def to( group: Group ) = group.add( this );
}

var element = new TestElement( datatype, "subject", 1, 1 );

What I need from the method in question, is to get a Map or two Collections of values.

var element.method                                       // the function I need
ret: ( ("subject", "subject"), ("day", 1), ("time", 1) ) // its output

Answer 1

It's time for bed, so I don't have time for a full answer, but look at the results of element.getClass.getFields (or getDeclaredFields for private fields) - you can call getValue(element) on the Field objects to fetch their values.

---

Awake now, and still no better answer, so:

First, note that in Java terms, your class doesn't have a public field subject, what it has is a private field subject and accessor methods subject() and subject_$eq(String).

You can iterate over the private field objects as described above, populating a Map from the pairs:

def getFields(o: Any): Map[String, Any] = {
  val fieldsAsPairs = for (field <- o.getClass.getDeclaredFields) yield {
    field.setAccessible(true)
    (field.getName, field.get(o)) 
  }
  Map(fieldsAsPairs :_*)
}

Now you can either define this method on TestElement (replacing o with this), or more generally usefully define a conversion so that you can call getFields on any reference

implicit def any2FieldValues[A](o: A) = new AnyRef {
  def fieldValues = getFields(o)
}

So that

element.fieldValues 

will give the result you want.