I'm trying to access variables of an object by using strings whose values are determined at run time.
Basically the object is used as a dictionary, and now I want to dynamically poll values from that dictionary
A simplified example:
object Something extends scala.AnyRef {
final val zero = 0
final val one = 1
final val two = 2
}
I would then principally like to do the following
Somthing."zero"
and get 0 in return.
Ideally I would like to use scala reflection for this
WARNING: Please heed Jörg W Mittag's advice before following my answer:
Scala heavily prefers type-safe compile-time reflection. So, using reflection in this way is not the Scala way. The Scala way would probably be to use compile-time reflection to generate all those pattern match cases
Using reflection Something.getClass.getDeclaredMethods.foreach(println) gives:
public final int example.Something$.zero()
public final int example.Something$.one()
public final int example.Something$.two()
so to get the names we can do
Something.getClass.getDeclaredMethods.map(_.getName) // Array(zero,one,two)
and to get the value
Something.getClass.getMethod("zero").invoke(Something) // 0
Defining the following implicit class
implicit class AccessMembersByReflectionName(something: Something.type) {
def get(name: String): AnyRef = {
Something.getClass.getMethod(name).invoke(Something)
}
}
cleans up the call site
Something.get("zero") // 0
As @n.m. already pointed, if you only want to retrieve values of the same type given an string key, you should use a Dictionary.
However, if for some reason you still need an object, you could accomplish something similar of what you want with this method.
Object Something {
val Zero: Int = 0
val One: Int = 1
val Three: Int = 3
def getValueByString(valName: String): Int = valName.toLowerCase match {
case "zero" => Zero
case "one" => One
case "three" => Three
}
}
EDIT I just read that you can modify the object, you still can make a function that will receive the object and the valName as a string.
