Reference to non-existent field 'mathworks'

I've been writing Matlab code that generates XML script. I haven't run into any problems until I try to bring data from another script into the XML writing one. I have researched the problem and tried their fixes, like replacing load() with importdata(), removing all clc and clear commands, etc. The error in particular occurs on the line

docNode = com.mathworks.xml.XMLUtils.createDocument('XMLName');

Matlab gives an error "Reference to non-existent field 'mathworks'". I can't seem to find any solutions that I haven't tried and don't know what else to do. If I try running the script without any data being imported it works without any problems. What could be blocking Matlab from being able to read its own XMLUtils files? I can answer any questions you have about the code itself, but cannot upload the code for security reasons.

[Geoff Hayes]

Jake - which version of MATLAB are you using? I'm running R2014a on OS X, and when I run the following (in the command window)

 >> methods view com.mathworks.xml.XMLUtils

I observe a list of all the methods for this class. What do you see when you try the same?

[Jake Conley]

I am running Matlab R2015b. When I run the above in my command window, I hit an error:

>> methods view com.mathworks.xml.XMLUtils  
Error using methods
Unknown command option.

Did I input the command wrong? I am not too familiar with the proper syntax for the methods function.

[Geoff Hayes]

my bad - I should have looked more closely at what I pasted (there was some auto-correction and so the method is methodsview, one word)

 >> methods view com.mathworks.xml.XMLUtils

[Jake Conley]

Thank you for the help Geoff! Jan solved the problem, turns out I was using "com" as a variable that Matlab was trying to call in the docNode line.

Cheers!

Answer 1

[Jan]

Does a variable named "com" exist in your code? Perhaps it is created by a load? Check this by using the debugger: Type this in the command window

dbstop if error

and run your code again. When it stops, check "com":

which com -all

[EDITED] After your comment:

As Geoff has said already: If com is a struct, the command with the same name is shadowed and cannot be called. This is the same as:

sum = 1
sum(1:5)  % error, because "sum" is a variable now

There are some solutions:

1. Use another name for the variable. This is the best.

2. Clear the variable temporarily:

comback = com;
clear('com');
docNode = com.mathworks.xml.XMLUtils.createDocument('XMLName');
com = comback;  % Huh, ugly.

3. Try if builtin gets the correct function:

docNode = builtin('com.mathworks.xml.XMLUtils.createDocument', 'XMLName');

I cannot test this currently, but it does not look nice also. Prefer not to shadow builtin function names by local variables.

[Jake Conley]

"com" is a 1x8 structure generated by the first script. Checking "com" when the XML script hits the error shows no changes to "com". Using which com -all results in "com is a variable".

There is one structure loaded by the first script using the importdata() function, but it is not required by the XML writing script. I have tried the importdata() and load() functions with the same results. The loaded structure is a 1x1 structure with 8 fields, each with a 10x1 array of values.

When running dbstop if error, the XML writing script hits the same error of:

Reference to non-existent field 'mathworks'.

Error in ScriptName(line 3)

docNode = com.mathworks.xml.XMLUtils.createDocument('XMLName');

I also checked the file and product requirements to see if there was a missing file required to run the script, but the fList just has the script location (no other required files) and pList just has the base Matlab product:

Name: 'MATLAB'
        Version: '8.6'
  ProductNumber: 1
        Certain: 1

I know that this is a difficult question to debug without the full script and files available to test. Thank you for your help.

[Geoff Hayes]

Jake - is the variable com in the same workspace as you are trying to call

 docNode = com.mathworks.xml.XMLUtils.createDocument('XMLName');

If so, then it sounds like MATLAB is trying to use the com variable for com.mathworks... and since mathworks isn't a field in com, then the error makes sense. Try renaming com to something else.

[Jake Conley]

YOU GOT IT! Congratulations! I'm an idiot apparently, hahaha. That is exactly what Matlab was trying to do. I renamed "com" and the script runs without a problem.

Thank you!

[Jan]

See [EDITED] in my answer.