How do I find all the variables of a given class in the MATLAB workspace?

I would like to be able to find all the variables of a given class in MATLAB. The class could be a built-in or user-defined.

Answer 1

[MathWorks Support Team]

A function to find all the variables of a given class is not available in MATLAB.

As a workaround, one can use the following code to display all the variables of class "ClassName" in the Command Window:

s = whos; % Looks for all variables
data_collector = zeros(size(s)); % Pre-allocation

disp('List of ClassName Type variables')
for i = 1:length(s)
    k = s(i).class;
    data_collector(i) = strcmp(k,'ClassName'); 
    if data_collector(i) == 1 % Write variable name in the Command Window
        disp(s(i).name) % Display data
    end

end

Or,

s = whos; 

% find the objects with the type 'ClassName' from the workspace:
matches= strcmp({s.class}, 'ClassName');
my_variables = {s(matches).name}

This also applies to Simulnk Enumeration class. For example:

>> Simulink.defineIntEnumType('a',{'b','c','d'},[1,2,3],'DefaultValue','b','DataScope','Imported','AddClassNameToEnumNames',false) 
>> s = a.b;
>> t = 1;
>> vars = whos;
>> idx = ismember({vars.class}, 'a');
>> vars_double = vars(idx);

Then, "vars_double" will only include the variables "s".

[Stephen23]

A warning for anyone interested in writing efficient code:

"Avoid functions that query the state of MATLAB such as inputname, which, whos, exist(var), and dbstack. Run-time introspection is computationally expensive."

source: https://www.mathworks.com/help/matlab/matlab_prog/techniques-for-improving-performance.html

[Steven Lord]

That sounds like a reasonable enhancement request to file with Technical Support using the telephone icon in the upper-right corner of this page. In addition to telling Technical Support what you want them to enter into the enhancement database (allow who and whos to return only variables of a specific class) it would be useful to tell them why you want that and/or how you would use that functionality. That can help the development team understand how you expect the feature to behave and provide some additional motivation when they're prioritizing development work.