Comparing changes in value of input variable to function for every function call

Hi!

I have some issues making a routine that can compare an input variable in a new function call with the variable of the same name from a previous function call. The input variable is a struct for which the fields have been changed via a GUI. I need to compare the structs for every function call and track the changes in the fields to pass the changed field values on to other functions.

here is my code:

function Equipment_calls(Settings_file,Equipment_list,Equipment_libs)

%Comparing the each succesive settings file with the previous one to check
%which field has changed and using that so send the command further down
%the hierachy 



% THE LINES BELOW IS MY ATTEMPT TO MAKE THE FEATURE COMPARING THE VARIABLE/STRUCT FROM THE
% PREVIOUS FUNCTION CALL WITH THE VARIABLE/STRUCT FROM THE CURRENT FUNCTION
% CALL 
new_settings_file = Settings_file;
while 1
    if exist('previous_settings_file','var') ~= 1 || isequal(new_settings_file,previous_settings_file) 
        fprintf('No changes to the settings file');
    else 
    [~, ia, ib] = setdiff(new_settings_file, previous_settings_file);
    disp(Settings_file(ia))
    disp(Settings_file(ib))
    end  

    
%THE FOLLOWING LINES HANDLES THE FIELDS IN THE STRUCT
Settings_field = fieldnames(Settings_file);
%Code handling all the changed fields in the structs. 
for i = 1:length(Settings_field)
    if contains(Settings_field(i),'functions') 
        field = Settings_field(i);
        fieldname = sprintf('%s',string(field));
        if Settings_file.(fieldname).initialise_shutdown == 1 
           %Initialising equipment which correspond to the "Equipment_list"
           switch fieldname 
               case 'Generator_functions'
                    idx = find(contains(Equipment_list.EquipmentType,'Generator'));
                    Libpath = Equipment_libs{idx};
                    init_file = dir(join([Libpath,'\*init.m']));
                    cmd_file_string = dir(join([Libpath,'\*cmd.m']));
                    cmd_file_string = cmd_file_string.name; 
                    cmd_file_string = erase(cmd_file_string,'.m');
                    cmd_func = str2func(cmd_file_string);
                    run(init_file.name)
                    feval(cmd_func,Settings_file);
               case 'Scope_functions'
                    idx = find(contains(Equipment_list.EquipmentType,'Scope'));
                    Libpath = Equipment_libs{idx};
                    init_file = dir(join([Libpath,'\*init.m']));
                    cmd_file_string = dir(join([Libpath,'\*cmd.m']));
                    cmd_file_string = cmd_file_string.name; 
                    cmd_file_string = erase(cmd_file_string,'.m');
                    cmd_func = str2func(cmd_file_string);
                    run(init_file.name) 
                    feval(cmd_func,Settings_file);
               case 'Stage_functions'
                    idx = find(contains(Equipment_list.EquipmentType,'Stage'));
                    Libpath = Equipment_libs{idx};
                    init_file = dir(join([Libpath,'\*init.m']));
                    run(init_file.name)
           end 
        elseif Settings_file.(fieldname).initialise_shutdown == 0
            %Closing equipment which correspond to the "Equipment_list"
            switch fieldname 
               case 'Generator_functions'
                    idx = find(contains(Equipment_list.EquipmentType,'Generator'));
                    Libpath = Equipment_libs{idx};
                    close_file = dir(join([Libpath,'\*close.m']));
                    run(close_file.name)
               case 'Scope_functions'
                    idx = find(contains(Equipment_list.EquipmentType,'Scope'));
                    Libpath = Equipment_libs{idx};
                    close_file = dir(join([Libpath,'\*close.m']));
                    run(close_file.name) 
               case 'Stage_functions'
                    idx = find(contains(Equipment_list.EquipmentType,'Stage'));
                    Libpath = Equipment_libs{idx};
                    close_file = dir(join([Libpath,'\*close_y.m']));
                    run(close_file.name)
            end
        else 
            %Handling all other settings changes or calls to functions
            switch fieldname 
               case 'Generator_functions'
                    idx = find(contains(Equipment_list.EquipmentType,'Generator'));
                    Libpath = Equipment_libs{idx};
                    function_file = dir(join([Libpath,'insert changed field name here']));
               case 'Scope_functions'
                    idx = find(contains(Equipment_list.EquipmentType,'Scope'));
                    Libpath = Equipment_libs{idx};
                    function_file = dir(join([Libpath,'insert changed field name here']));
               case 'Stage_functions'
                    idx = find(contains(Equipment_list.EquipmentType,'Stage'));
                    Libpath = Equipment_libs{idx};
                    function_file = dir(join([Libpath,'insert changed field name here']));
            end
        end
    end    
end

The 'Settings_file' input contains the structs that are subject to change via the GUI.

Hope it makes sense

Best regards

Christoffer

[Walter Roberson]

where do you assign previous_settings_file?

[Christoffer Sørensen]

That’s one of my issues. I’m not sure how to define. Because the first time I call the function there is no previous value. It only the second time and onwards it should be a struct. I Have tried to follow this example: https://www.mathworks.com/matlabcentral/answers/638780-how-to-compare-previous-and-next-values-in-matlab

But I’m not sure whether it’s useful for what I want to do.

Answer 1

[Walter Roberson]

function Equipment_calls(Settings_file,Equipment_list,Equipment_libs)
%Comparing the each succesive settings file with the previous one to check
%which field has changed and using that so send the command further down
%the hierachy 
% THE LINES BELOW IS MY ATTEMPT TO MAKE THE FEATURE COMPARING THE VARIABLE/STRUCT FROM THE
% PREVIOUS FUNCTION CALL WITH THE VARIABLE/STRUCT FROM THE CURRENT FUNCTION
% CALL 

persistent previous_settings_file

new_settings_file = Settings_file;

if isempty(previous_settings_file); previous_settings_file = new_settings_file; end

while true
    if isequal(new_settings_file,previous_settings_file) 
        fprintf('No changes to the settings file');
    else 
        [~, ia, ib] = setdiff(new_settings_file, previous_settings_file);
        disp(Settings_file(ia))
        disp(Settings_file(ib))
    end  
    previous_settings_file = new_settings_file;

[Christoffer Sørensen]

This looks promising! I looked into the documentation of the "persistent" function and I think thats what I need! I will try to test it when im back at work.