Scala reflection to access all public fields at runtime
In brief:
import scala.reflect.runtime.universe._
val a = new A
val rm = scala.reflect.runtime.currentMirror
val accessors = rm.classSymbol(a.getClass).toType.members.collect {
case m: MethodSymbol if m.isGetter && m.isPublic => m
}
val instanceMirror = rm.reflect(a)
for(acc <- accessors)
println(s"$a: ${instanceMirror.reflectMethod(acc).apply()}")
You can you TypeTag to get an access:
scala> import scala.reflect.runtime.universe._
import scala.reflect.runtime.universe._
scala> class A {
| val x = 3
| val y = 4
| }
defined class A
scala> class B extends A {
| val z = 5
| }
defined class B
scala> typeOf[B]
res0: reflect.runtime.universe.Type = B
Now you have two options: members
which shows all members (even inherited ones) and declarations
(only defined in the current class), e.g:
scala> res0.declarations
res2: reflect.runtime.universe.MemberScope = SynchronizedOps(constructor B, value z, value z)
If you want to work with this field you need reflect them through InstanceMirror:
scala> val b = new B
b: B = B@6ebe10dd
scala> val currentMirror = runtimeMirror(getClass.getClassLoader)
.....
scala> val bMir = currentMirror.reflect(b)
bMir: reflect.runtime.universe.InstanceMirror = instance mirror for B@6ebe10dd
Now you just need to get a Symbol you need, e.g you want to get a value of z
varible:
scala> val zt = typeOf[B].declaration("z": TermName).asMethod
zt: reflect.runtime.universe.MethodSymbol = value z
scala> bMir.reflectField(zt).get
res20: Any = 5