Is it possible to use Attributes on Delphi method arguments?

Question

Is this valid code with newer Delphi versions?

// handle HTTP request \"example.com/products?ProductID=123\"
procedure TMyRESTfulService.HandleRequest([QueryPara         


        

Answer 1

Yes you can:

program Project1;

{$APPTYPE CONSOLE}

uses
  Rtti,
  SysUtils;

type
  QueryParamAttribute = class(TCustomAttribute)
  end;

  TMyRESTfulService = class
    procedure HandleRequest([QueryParam] ProductID: string);
  end;

procedure TMyRESTfulService.HandleRequest(ProductID: string);
begin

end;

var
  ctx: TRttiContext;
  t: TRttiType;
  m: TRttiMethod;
  p: TRttiParameter;
  a: TCustomAttribute;
begin
  try
    t := ctx.GetType(TMyRESTfulService);
    m := t.GetMethod('HandleRequest');
    for p in m.GetParameters do
      for a in p.GetAttributes do
        Writeln('Attribute "', a.ClassName, '" found on parameter "', p.Name, '"');
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
  Readln;
end.