How to add more parameters to callback function.

I want to add the new parameter 'a' to myfunction(obj,event_obj,a). I dont understant why there are no parameters at calling while the function has arguments.

How to call the function with 'a' parameter also?

Here is the code that is working without my new parameter:

function button_exponential_fit_Callback(hObject, eventdata, handles)
...
set(dcm, 'updatefcn', @myfunction)

function output_txt = myfunction(obj,event_obj)
pos = get(event_obj,'Position');
output_txt = {['X: ',num2str(pos(1),4)], ['Y: ',num2str(pos(2),4)]};
%disp(a)

Answer 1

[Adam Danz]

The first two inputs for callback functions are fixed. You can add additional inputs by doing the following.

function button_exponential_fit_Callback(hObject, eventdata, handles)
...
set(dcm, 'updatefcn', {@myfunction, a})
%                     ________________   In curly brackets, add additional inputs


function output_txt = myfunction(obj,event_obj,a)
%                                             ___  starting with input #3
end

[Sanders A.]

I can't get this to work in my case

o.connection = udpport("datagram",'LocalHost',o.ServerName);%, 'DatagramTerminateMode', 'on', 'EnablePortSharing', 'on');
configureCallback(o.connection,"datagram",1,@receiver)

where

function receiver(h, ~, o)

needs object "o" to exist persistently; currently it does not. If I try changing @receiver to {@receiver,o}, I get the following error

Expected input to be one of these types:
function_handle
Instead its type was cell.

The {@receiver,o} syntax used to work with "udp", but I can't find any resources on how to make it work with this newfangled "udpport"

This is attempting to help update https://github.com/fsaxen/ParforProgMon/issues/12 per the dropping of "udp" for "udpport". I truly have no idea what I'm doing, but this is where I've gotten to... I think I have updated the rest of the syntax per https://www.mathworks.com/help/releases/R2022a/instrument/transition-your-code-to-udpport-interface.html

[Adam Danz]

This is difficult to troubleshoot without being connected to a UDP socket. Add a second argument in receiver(h,a,o), but a break point in the callback function, and tell us what you see in h, a, and o. What class are they (class()), size, etc.

[Sanders A.]

Changing it to the following per https://www.mathworks.com/help/matlab/matlab_oop/listener-callback-functions.html (I think there is a missing ')' at end of first code segment of section: Additional Arguments for Callback Function)

o.connection = udpport("datagram",'LocalHost',o.ServerName, 'EnablePortSharing', true);
configureCallback(o.connection,"datagram",1,@(srv,evnt)receiver(srv,evnt,o))

with

function receiver(h, ~, o)

worked for the correct transfering of the data, but now the issue is that none of the receiver callbacks are processsed (while in the correct manner!) until the end of program, which kind of ruins the point.

Pausing the program in the receiver function and then clicking "show all properties" for o.connection gives the following:

IPAddressVersion: "IPV4"
LocalHost: "192.168.56.1"
LocalPort: 64416
NumDatagramsAvailable: 11

ByteOrder: "little-endian"
Timeout: 10

EnablePortSharing: 1
EnableBroadcast: 0
EnableMulticast: 0
EnableMulticastLoopback: 1
MulticastGroup: ""

DatagramsAvailableFcnMode: "datagram"
DatagramsAvailableFcnCount: 1
DatagramsAvailableFcn: @(srv,evnt)receiver(srv,evnt,o)
OutputDatagramSize: 512
NumDatagramsWritten: 0

ErrorOccurredFcn: []
UserData: []

Of note are "NumDatagramsAvailable" being 11 while "DatagramsAvailableFcnCount" is set to 1. Given the latter property, I would have expected the receiver function to have run each time NumDatagramsAvailable >= DatagramsAvailableFcnCount, but given this is my first foray into udp, I must be mistaken. Might you be able to help me with this new issue?

Thank you very much!!!

Edit to add: The "client" is created as such following the original code, if it means anything. Does it need to have special options?

o.connection = udpport("datagram",'LocalHost',o.ServerName);

It was originally

o.connection = udp(o.ServerName, o.ServerPort); 
fopen(o.connection);

[Adam Danz]

I'm afraid my experience with this is limited and without being able to troubleshoot I am limited to the documentation and reading the code.

Your callback should trigger whenever a new datagram is available to be read. Could it be that all 11 available diagrams are already available before the callback function is defined?

If that doesn't help getting you closer, you can contact tech support for help. Feel free to include the URL of this thread or at least copy its contents to show what you've tried.

Answer 2

[Steven Lord]

I know the cell array approach @Adam Danz suggested for passing additional parameters into a callback function works for callbacks of Handle Graphics objects, but I'm not certain it will work for callbacks of UDP objects. I'd probably use the Adapter pattern with an anonymous function. Since I'm not familiar with UDP I'm going to use a graphical example as well but I expect the technique will work with UDP.

The fsurf function requires the function handle you provide it as input to accept two arguments, x and y.

fsurf(@(x, y) x.^2-y.^2)

But if I had a function with three inputs:

f = @(x, y, a) x.^2+a*y.^2;

I could still use this in fsurf. I would just need an adapter that allows fsurf to call the function with two inputs and that calls f with three inputs.

figure
adaptedF = @(x, y) f(x, y, -1);
fsurf(adaptedF)