Hi! I am developing MDI application with help of wxErlang. I have a parent frame, implemented as wx_object: -module(main_frame). -export([new/0, init/1, handle_call/3, handle_event/2, terminate/2]). -behaviour(wx_object). .... And I have a child frame, implemented as wx_object too: module(child_frame). -export([new/2, init/1, handle_call/3, handle_event/2, terminate/2]). -export([save/1]). -behaviour(wx_object). % some public API method save(Frame) -> wx_object:call(Frame, save). .... I want to call save/1 for an active child frame from the parent frame. There is my code: ActiveChild = wxMDIParentFrame:getActiveChild(Frame), case wx:is_null(ActiveChild) of false - child_frame:save(ActiveChild); _ - ignore end This code fails because ActiveChild is #wx_ref{} with state=[], but wx_object:call/2 needs #wx_ref{} where state is set to the pid of the process which we call. What is the right method to do this? I thought only to store a list of all created child frames with its pids in the parent frame and search the pid in this list, but this is ugly.