Initial annotation example that creates companion object to access pa…

…rameter names by String

build.sbt

@@ -1,3 +1,3 @@
+scalaVersion := "2.11.2"
 
-scalaVersion := "2.11.0-M5"
-
+addCompilerPlugin("org.scalamacros" % "paradise" % "2.0.1" cross CrossVersion.full)

macro/build.sbt

@@ -1,3 +1,3 @@
+scalaVersion := "2.11.2"
 
-scalaVersion := "2.11.0-M5"
-
+addCompilerPlugin("org.scalamacros" % "paradise" % "2.0.1" cross CrossVersion.full)

macro/src/main/scala/Macros.scala

@@ -1,6 +1,54 @@
+import scala.annotation.StaticAnnotation
 import scala.language.experimental.macros
-import scala.reflect.macros.Context
+import scala.reflect.macros.whitebox.Context
 
-object Macros {
-  // write macros here
+class fieldNames extends StaticAnnotation {
+  def macroTransform(annottees: Any*) = macro fieldNamesMacro.impl
 }
+
+object fieldNamesMacro {
+  def impl(c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
+    import c.universe._
+    import termNames.CONSTRUCTOR
+    import typeNames.EMPTY
+
+    val inputs = annottees.map(_.tree).toList
+    val (expanded, objName, accessorFields) = inputs match {
+      case (param: ClassDef) :: (tail)  => {
+        val constructAccessor = param.collect {
+          case (values: ValDef)
+            if values.mods.hasFlag(Flag.PARAMACCESSOR) &&
+              !values.mods.hasFlag(Flag.PRIVATE) &&
+              !values.mods.hasFlag(Flag.CASEACCESSOR) => {
+            values
+          }
+        }
+        val stringDef = constructAccessor.map { field ⇒
+          val name = field.name.toTermName
+          val decoded = name.decodedName.toString
+          q"val $name: String = $decoded"
+        }
+        (inputs, Some(param.name.decodedName.toString), Some(stringDef))
+      }
+      case (_) => (inputs, None, None)
+    }
+
+    val companionObject = for {
+      accessorFieldsStringValues <- accessorFields
+      if accessorFieldsStringValues.length > 0
+    } yield {
+      val constructorBody = Block(List(Apply(Select(Super(This(EMPTY), EMPTY), CONSTRUCTOR), List())), Literal(Constant(())))
+      val constructor = DefDef(NoMods, CONSTRUCTOR, List(), List(List()), TypeTree(), constructorBody)
+      val objInheritance = List(Ident(TypeName("AnyRef")))
+      ModuleDef(NoMods, TermName(objName.getOrElse("Zombie")),
+        Template(objInheritance, noSelfType, constructor :: accessorFieldsStringValues))
+    }
+
+    val completeBlock = companionObject match {
+      case Some(x) => Block(expanded :+ x,Literal(Constant(())))
+      case _ => Block(expanded, Literal(Constant(())))
+    }
+    c.Expr[Any](completeBlock)
+  }
+}
+

src/main/scala/Main.scala

@@ -1,5 +1,10 @@
 object Main extends App {
-  import Macros._
 
-  println("it works!")
+  @fieldNames
+  case class Person(name: String, age: Int)
+
+  @fieldNames
+  class Address(street: List[String])
+
+  println(s"${Person.name} ${Person.age} ${Address.street}")
 }