Reading metadata in a Haxe macro

Question

I would like to know how to read metadata from a class (and its methods) in a macro.

I tried to modify this example. I added : to see if metadata without them is only available in generated code, but nothing.. I have an empty result in all three cases.. Any ideas?

@:author("Nicolas")
@debug
class MyClass {
    @:range(1, 8)
    var value:Int;

    @broken
    @:noCompletion
    static function method() { }
}

class Boot {
    static public function main() {
        test();
    }

    macro public static function test() {
        trace(haxe.rtti.Meta.getType(MyClass)); // { author : ["Nicolas"], debug : null }
        trace(haxe.rtti.Meta.getFields(MyClass).value.range); // [1,8]
        trace(haxe.rtti.Meta.getStatics(MyClass).method); // { broken: null }
        return haxe.macro.Context.makeExpr({}, haxe.macro.Context.currentPos());
    }
}

Rounders

Answer 1

In order to access the types from a macro, you need to use the haxe.macro.* API rather than accessing haxe.rtti. The following example will trace both debug and author, which are the metadata applied to MyClass:

class Boot
{
  macro public static function test()
  {
    switch (haxe.macro.Context.getType("MyClass"))
    {
      case TInst(cl,_):
        trace(cl.get().meta.get());
      case _:
    }
  }
}

In order to get class field metadata, you must go through all fields from cl.get().fields.get().

See Context.getType(), ClassType and MetaAccess.

Hanschen

Pretty new to this, but could you elaborate where the cl and _ comes from? (ex: in case TInst(cl,_): and case _:) – Fillip

@bigp have a look at the pattern matching documentation ( at haxe.org/manual/lf-pattern-matching.html ) – Hanschen