Class definition not updated after path change

Hi,

I'm having trouble with class definition update when I change Matlab path within a script.

Let's illustrate with a simple exemple.

I have these folders in my workspace, none of them are in the Matlab path.

The myClass class is as simple as it can be. The one in the FolderA is defied as below :

classdef myClass
    properties
        FolderAprop
    end
end

And the one in FolderB :

classdef myClass
    properties
        FolderBprop
    end
end

When I change the Matlab path to use the FolderB class instead of Forlder A class within a script, the class definition doesn't updates if one instance of the class is in the workspace. The code below, all within a script called testClassUpdate.m, shows it :

clear all

addpath ./FolderA
which myClass
myClassInstA = myClass;
properties(myClassInstA)

rmpath ./FolderA
addpath ./FolderB

which myClass
myClassInstB = myClass;
properties(myClassInstB)

rmpath ./FolderB

It returns :

>> testClassUpdate
L:\tmp\TestPathClass\FolderA\@myClass\myClass.m  % myClass constructor
Properties for class myClass:
    FolderAprop

L:\tmp\TestPathClass\FolderB\@myClass\myClass.m  % myClass constructor
Properties for class myClass:
    FolderAprop

But when I execute the exact same code in two times, returning the the prompt after addpath ./FolderB, it works as expected :

>> clear all
addpath ./FolderA
which myClass
myClassInstA = myClass;
properties(myClassInstA)
rmpath ./FolderA
addpath ./FolderB

L:\tmp\TestPathClass\FolderA\@myClass\myClass.m  % myClass constructor
Properties for class myClass:
    FolderAprop

>> which myClass
myClassInstB = myClass;
properties(myClassInstB)
rmpath ./FolderB

L:\tmp\TestPathClass\FolderB\@myClass\myClass.m  % myClass constructor
Properties for class myClass:
    FolderBprop

I tried to call the rehash function but it has no effect. If I clear all instances of myClass after changing path, it works as expected but I try to avoid that.

I read the two following help pages and, if I understand correctly, the class definition should have been updated as I put my class files in @ folders.

Changing Path to Update Class Definition

Automatic Updates for Modified Classes

Do anyone knows how to get my class definition updated correctly ?

Regards,

Julien

Answer 1

[per isakson]

I have reproduced the behavior on R2018a.

The following script

%%testClassUpdate
clear all
addpath ./FolderA
[~] = which('myClass');
myClassInstA = myClass;
disp( properties(myClassInstA) )
clear myClass
rmpath ./FolderA
addpath ./FolderB
[~] = which('myClass');
myClassInstB = myClass;
disp( properties(myClassInstB) )
rmpath ./FolderB

When I run the entire script in one go (F5) it displays

    'FolderAprop'
    'FolderAprop'

However, when I run it section by section (Cntrl+Shift+Enter) it displays

    'FolderAprop'
    'FolderBprop'

I get identical results even without the clear myClass

IMO: This is a case for Tech Support.

[Christoph Hüsson]

i ran into the same issue. you need to clear existing variables that use type-definitions you are about to update. read this, especially the section "Changing Path to Update Class Definition":

https://de.mathworks.com/help/matlab/matlab_oop/organizing-classes-in-folders.html

I am using sth like this to remove only those workspace variables, which would potentially be affected:

% https://de.mathworks.com/matlabcentral/answers/96201-how-do-i-access-a-base-workspace-variable-from-within-a-function

currVars = evalin('base', 'whos');

zimVars = {};

for v = 1:length(currVars)

if startsWith(currVars(v).class, 'ZimV.')

zimVars{end + 1} = currVars(v).name;

end

end

if ~isempty(zimVars)

if ~NameValueArgs.keepConflictingVaraibles

% https://stackoverflow.com/questions/20167762/evalin-with-variable-matlab

% required because we are going to remove them from inside a evalin-call

assignin('base', 'zimVars', zimVars);

warning('Removing variables from your workspace that require classes of this package. If you do NOT want this for future calls, use keepConflictingVaraibles=true')

evalin('base', 'clear(zimVars{:}); clear zimVars');

else

warning('There are variables in your workspace that require updates to class-definitions of this package. You might experience unexpected behavior, as existing variables might use stale definitions. Read more about this here (especially section "Changing Path to Update Class Definition"): https://de.mathworks.com/help/matlab/matlab_oop/organizing-classes-in-folders.html')

end

end