Passing variable from event handler - matlab

Question

I would be very grateful for help, advice or suggestion. I have an application to control geodetic instrument using synchoronous interface. However some commands are asynchronous by its nature, e.g. GetReflectors. After this command is triggered I receive as many server answers as is the number of available reflectors. So I have registered an COM event and associate handler function. So far so good. I can display the data coming but I do not know how to pass some variable to the main function. I tried to save variable as .mat file or in .txt file and read it. Actually it works in Matlab but it does not works in compiled .exe aplication (Error firing event). Even disp command does not work in compiled aplication (display nothing). So the main question is: how to pass variables from handler to main function. Is there a way? Global variables? Thank you Filip
Edit: I am adding an code to demostrate the problem... I need to save Reflector Name and Reflector ID so as the user can choose one (because there are multiple events coming with different Reflectors).
function pushbutton_GetReflectors_Callback(hObject, eventdata, handles)
ltsync = actxserver ('LTControl.LTCommandSync2'); %Act as server: LTConnect2
ltsync.events() %List of all COM events
ltsync.registerevent({'ReflectorsData' 'ReflectorsHandler'}) %Register event
ltsync.GetReflectors() %Ask instrument for reflectors
pause(3) %Time to receive answers
end
function ReflectorsHandler(varargin) %Handler of the event ReflectorsData
%var1,var2,reflectorID,reflectorName,var5,surfaceOffset,reflectorsTotal,var8,var9
disp('Reflector Data:');
disp(varargin{3}) %Reflector ID
disp(varargin{4}) %Reflector name
end

Answer 1

I believe you can solve this problem by passing a function handle to registerevent instead of just the string function name, and creating a class to allow you to pass the data back. First, the class:
classdef ReflectorsResponse < handle
properties (SetAccess = private)
reflectors
responseComplete = false;
reflectorsTotal = NaN;
end
methods
function respond(obj, varargin)
% Create a struct for each reflector (or you could define
% another class, but let's keep it simple for the time being)
newRefl = struct();
newRefl.ID = varargin{3};
newRefl.name = varargin{4};
newRefl.surfaceOffset = varargin{6};
% ... store other properties in struct
% Store this reflector
obj.reflectors = [obj.reflectors; newRefl];
% Store total reflector count and check for completion
if isnan(obj.reflectorsTotal)
obj.reflectorsTotal = varargin{7};
end
if length(obj.reflectors) == obj.reflectorsTotal
obj.responseComplete = true;
end
end
end
end
You can then use this by making the respond method your handler:
function pushbutton_GetReflectors_Callback(hObject, eventdata, handles)
% Create the response object and associated handler function handle
response = ReflectorsResponse();
handlerFun = #(varargin)response.respond(varargin{:});
ltsync = actxserver ('LTControl.LTCommandSync2'); %Act as server: LTConnect2
ltsync.events() %List of all COM events
ltsync.registerevent({'ReflectorsData' handlerFun}) %Register event
ltsync.GetReflectors() %Ask instrument for reflectors
% Wait for request to complete
while ~response.responseComplete
pause(0.1);
drawnow update;
% NOTE: Should add a timeout to this loop
end
% Do stuff with response.reflectors
end
This will wait until there has been a response for each of the reflectors, the number of which is determined from the first response. Note that you should add a timeout to the while loop, otherwise you risk waiting infinitely.
If there are lots of these asynchronous requests that you have to handle, I would suggest encapsulating the entire request/response sequence (including the creation of the ActiveX server, setup of the event handler, and waiting for the response(s)) in a generalised base class, and deriving specific subclasses for each different request.