CODEWITHSUNDEEP
scalamacrosscala-macrosscala-macro-paradise
ayvango
ayvango

Reputation: 5977

How to pass parameters to annotation with macro expansions

I'm using macros annotation for generating code. I would like to change its behaviour based on additional string parameters. So it would produce different results for same code. I closely followed the guide for macro annotations that covers only the simplest use.

@myMacros
class MyClass {
}

That is how I'm using macroses now. And what I'd like to achieve:

@myMacros(name : String)
class MyClass {
}

Upvotes: 0

Views: 378

Answers (1)

余杰水
余杰水

Reputation: 1384

you can use macroApplication 

class AnnotationPassVal(val name: String) extends StaticAnnotation {
  def macroTransform(annottees: Any*): Any = macro AnnotationPassValImpl.apply
}

class AnnotationPassValImpl(val c: Context) {

  import c.universe._

  def showInfo(s: String) =
    c.info(c.enclosingPosition, s.split("\n").mkString("\n |---macro info---\n |", "\n |", ""), true)

  def apply(annottees: c.Expr[Any]*) = {
    val a = c.macroApplication

    //look macroApplication is what 
    showInfo(show(a))


    val AnnotationName: Tree = a match {
      case q"new AnnotationPassVal(name = $name).macroTransform(..$a)" =>
        name: Tree
    }

    showInfo(show(AnnotationName))
    q"""{..$annottees}"""
  }
}

test

@AnnotationPassVal(name = "hello")
class AnnotationPassValTest //when show info "hello"

Upvotes: 1

Related Questions