Insert one method invocation into many other methods - scala

Question

I need to add a method to some other methods in the application. There are quite a lot of them. Is there any sensible way to do that except the straightforward one -- inserting the method call into each method manually?

Answer 1

See this answer for implementation with def macros.
Implementation with macro annotations:
import scala.reflect.macros.Context
import scala.language.experimental.macros
def wrappedImpl(c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
import c.universe._
import scala.reflect.internal.Flags._
object DefMods{
def unapply(mods: Modifiers): Option[Modifiers] = {
val fs = mods.flags.asInstanceOf[Long]
if ((fs & DEFERRED) == 0 && (fs & STABLE) == 0) Some(mods)
else None
}
}
def wrap(t: Tree) = t match {
case DefDef(DefMods(mods), name, tparams, vparams, tpt, body) if name != nme.CONSTRUCTOR =>
DefDef(mods, name, tparams, vparams, tpt,
q"""
println("before")
val res = $body
println("after")
res""")
case x => x
}
def transform(t: Tree) = t match {
case ClassDef(mods, name, tparams, Template(parents, self, methods)) =>
ClassDef(mods, name, tparams, Template(parents, self, methods.map{wrap(_)}))
case x => x
}
c.Expr[Any](Block(annottees.map(_.tree).map(transform(_)).toList, Literal(Constant(()))))
}
import scala.annotation.StaticAnnotation
class wrapped extends StaticAnnotation {
def macroTransform(annottees: Any*) = macro wrappedImpl
}
You'll have to use a compiler plugin for quasiquotes.
Usage:
#wrapped class Test {
def test() = println("test")
}
scala> new Test().test()
before
test
after