How can I get the path of the file being loaded when implementing the loadobj method

When implementing a load object method with:

a = loadobj(b)

I would like to be able to get the path of the orinial file which caused this object to load.

Example code:

classdef MockObj
    methods (Static)
         function obj = loadobj(s)
            FilePath = SolutionCode();
            disp("The obj was loaded from " + FilePath );
            obj = s;
         end
    end % methods
end % classdef

When loading a saved file containing an instance of MockObj, I would like to print the location of this file, from within the method.

I'm missing the

SolutionCode()

which will give me the fullpath of the file which caused MockObj to load.

Edited (2020-08-26):

For clarifications:

The file is the .mat file which MATLAB creates when you save your workspace.

Once it is saved, you can move your file to whatever folder.

When you load a file that contains an instance of MockObj class, the loadobj(s) method is being called.

Unfortunately, once you’re inside the method, it seems as if you’ve lost any information about the .mat file. You can only access the variable s, which is the object itself.

That’s what I’m looking for.. A way to figure out something about the .mat file which caused the method loadobj(s) of my MockObj class.

Any other solution is also blessed.

Thanks in advance,

Nir G.

Answer 1

[per isakson]

A little demo

>> clearvars
>> create_and_save_mock_obj
>> load_mock_obj
The obj was loaded from D:\m\cssm\load_mock_obj.m

so far so good

>> load mock_obj.mat
Index exceeds array bounds.
Error in SolutionCode (line 3)
    ffs = which(stk(1).file);
Error in MockClass.loadobj (line 4)
            FilePath = SolutionCode(); 

a test is needed whether the variable stk is empty; loading from the base workspace.

Code

function    ffs = SolutionCode()
    stk = dbstack(2);
    ffs = which(stk(1).file);
end

function    create_and_save_mock_obj
   mock_obj = MockClass(); 
   save('mock_obj.mat', 'mock_obj' );
end

function    load_mock_obj
    S = load('mock_obj.mat'); %#ok<*NASGU>
end

and MockClass is identical to you MockObj

[Nir Gutman]

Thanks for the proposed solution.

Unfortunately, it works only when I run it as one script, but fails to give the correct path if I, for example, move the file manually to a different folder and tries to open it from there.

Any ideas?

Most grateful,

Nir G.

[per isakson]

"run it as one script" What script?

"move the file manually" What file?

What did you do and what happend? And what did you want to happen?

[Nir Gutman]

I did:

1. I Saved the Object to a file named "mock_obj". (The default folder for where files are saved is the current folder of MATLAB (pwd) ). Let's say the folder is "C:\first" .
2. I Moved the file manually to a different folder. Let's say the folder is "C:\second".
3. I've loaded the file from its new location.

what happend:

% The obj was loaded from C:\Program Files\MATLAB\2019b\toolbox\matlab\codetools\uiimport.m

What I've wanted to happen:

% The obj was loaded from C:\second

Thanks again for the help,

Nir G.

[per isakson]

Your description assumes a context, which I don't share. I need more details. My understanding

• "mock_obj" is not a file, it's a variable. Do you mean "mock_obj.mat"?
• "moved the file manually" Does "file" refer to "mock_obj.mat"?
• "I've loaded the file from it's new location" What exactly did you do?

A literal interpretation of what you did

>> load_mock_obj
The obj was loaded from D:\m\cssm\load_mock_obj.m

I moved mock_obj.mat to another folder, which is on the search path

>> load_mock_obj
The obj was loaded from D:\m\cssm\load_mock_obj.m
>> 

Discussion:

• "% The obj was loaded from C:\second". My solution did never solve your problem: "When loading a saved file containing an instance of MockObj, I would like to print the location of this file, from within the method." I misinterpreted this sentence.
• "Unfortunately, it works only when I run it as one script" This fooled me. I would say it never works. You ask for a folder and my "solution" returns a full file specification.
• I failed to reproduce what you did.
• I'm confused (at a higher level)! Are these two sentences of your question consistent? When loading a saved file containing an instance of MockObj, I would like to print the location of this file, from within the method." and "which will give me the fullpath of the file which caused MockObj to load." I would say no, they are not consistent. My solution aimed at the objective of the second sentence.

[Nir Gutman]

I'm sorry that it was confusing, and I hope the following explanation might clear thing up:

As You’ve guessed, the file is the .mat file which MATLAB creates when you save your workspace.

Once it is saved, you can move your file to whatever folder.

When you load a file that contains an instance of MockObj class, the loadobj(s) method is being called.

Unfortunately, once you’re inside the method, it seems as if you’ve lost any information about the .mat file. You can only access the variable s, which is the object itself.

That’s what I’m looking for, a way to figure out something about the .mat file which caused the method loadobj(s) of my MockObj class.

I hope it makes sense,

Nir G.

[per isakson]

Thanks, now I understand, however I have no solution.

Answer 2

[Matt J]

But why would this information be more useful to you in the loadobj workspace than in the workspace where you actually invoke the load() command? When the load command is invoked, you have the name of the .mat file and can do any addditional manipulations you want with it right then and there. If the code for these extra manipulations would be repetitive, then you can use an ordinary wrapper function or method to do the loading:

function   S = load_custom(filename)

    [pth,fname]=fileparts(which(filename));
    
    FilePath=fullfile(pth,fname);

    S = load(FilePath);
    
    disp("The file contents were loaded from " + FilePath );
    
end

[Nir Gutman]

The thing is... My object needs to know where is the .mat file.

But I am not the one who is doing the loading. Loading the file can be caused by (For example):

• a third party code
• double clicking the file in Explorer

[Matt J]

Are you the one doing the saving? The only thing I can think of is at the time of saving you write the .mat file name to a class property...

[Nir Gutman]

Thanks for the reply.

I'm the one doing the saving, and I keep and know the location and name of the .mat file at the moment of saving.

Unfortunately, when the file is being moved to another folder and then being loaded, the information is no longer valid.

Any ideas?

Thanks,

Nir G.

[Matt J]

My only idea, I'm afraid, is to submit an enhancement request to TMW to pass the source/destination matfile name to loadobj/saveobjas additional input arguments... I think it would open lots of useful possibilities!