Example MATLAB class wrapper for a C++ class

An example of how to safely encapsulate a C++ class in a MATLAB class, via a mex interface.

Description

This package provides an example of how to wrap a C++ class in a MATLAB class, via a mex interface, safely, without memory leaks, whilst achieving an interface in MATLAB that is similar to the underlying C++ interface.

After downloading, first mex the C++ wrapper using:
>> mex class_interface_mex.cpp

Then test the various methods:
>> a = class_interface(); % Create a class instance
>> train(a) % Train the class - dummy method
>> test(a) % Test the class - dummy method
>> clear a; % Destroy the instance

Look in class_interface.m and class_interface_mex.cpp to see how this is implemented, and copy the structure to interface with your own C++ classes.

This submission is inspired by the following newsgroup thread:
http://www.mathworks.com/matlabcentral/newsreader/view_thread/278243
Thanks to all those who have contributed.

Acknowledgements

This file inspired Ray Casting For Deformable Triangular 3 D Meshes.

• MATLAB release: MATLAB 8.0 (R2012b)
• Other requirements: C++ compiler

[Oliver Woodford]

Szigeti: your compile error is not related to this submission.

Fernando: the error you get seems self explanatory. You need to make sure class_handle.hpp, which comes with this submission, is in the same folder as the cpp file being compiled.

[Szigeti]

Hello
I have run the example successfully, and even managed to make new functions, in my class, and gave a matrix as an out parameter. However I want to import my code into the given class, as a function. It opens a dll in C++ to a COM 2 device. I have overloaded some operator like [], =, *; I have read that matlab support overloading, but this is not matlab code. So I am confused a bit. In my opinion the vs 2010 compiler that I have mex -setup-ed, should work. But it gives me this error. class_interface_mex.obj : error LNK2019: unresolved external symbol "public: class std::vector<int,class std::allocator<int> > & __cdecl EEGContainer::operator[](int)" (??AEEGContainer@@QEAAAEAV?$vector@HV?$allocator@H@std@@@std@@H@Z) referenced in function "public: double * * __cdecl dummy::getEeg(void)" (?getEeg@dummy@@QEAAPEAPEANXZ)
class_interface_mex.obj : error LNK2019: unresolved external symbol "public: int __cdecl EEGContainer::getDataLenght(void)" (?getDataLenght@EEGContainer@@QEAAHXZ) referenced in function "public: double * * __cdecl dummy::getEeg(void)" (?getEeg@dummy@@QEAAPEAPEANXZ)
class_interface_mex.obj : error LNK2019: unresolved external symbol "public: __cdecl EEGContainer::~EEGContainer(void)" (??1EEGContainer@@QEAA@XZ) referenced in function "public: double * * __cdecl dummy::getEeg(void)" (?getEeg@dummy@@QEAAPEAPEANXZ)
class_interface_mex.obj : error LNK2019: unresolved external symbol "public: class EEGContainer & __cdecl EEGContainer::operator=(class EEGContainer const &)" (??4EEGContainer@@QEAAAEAV0@AEBV0@@Z) referenced in function "public: double * * __cdecl dummy::getEeg(void)" (?getEeg@dummy@@QEAAPEAPEANXZ)
class_interface_mex.obj : error LNK2019: unresolved external symbol "public: __cdecl EEGContainer::EEGContainer(int)" (??0EEGContainer@@QEAA@H@Z) referenced in function "public: double * * __cdecl dummy::getEeg(void)" (?getEeg@dummy@@QEAAPEAPEANXZ)
class_interface_mex.obj : error LNK2019: unresolved external symbol "public: __cdecl BMRecorder::BMRecorder(void)" (??0BMRecorder@@QEAA@XZ) referenced in function "public: double * * __cdecl dummy::getEeg(void)" (?getEeg@dummy@@QEAAPEAPEANXZ)
class_interface_mex.mexw64 : fatal error LNK1120: 6 unresolved externals

[Fernando]

hello everyone, I am having trouble when mexing the class_interface_mex.cpp in matlab. The error that matlab gives me is the follwing:

>> mex class_interface_mex.cpp
class_interface_mex.cpp
\\aus.aero-ad.tamu.edu\UgradUsers$\f0p1107\Home\MATLAB\class_interface_mex.cpp(2) : fatal error C1083: Cannot open include file: 'class_handle.hpp': No such file or directory

C:\PROGRA~1\MATLAB\R2012A\BIN\MEX.PL: Error: Compile of '\\aus.aero-ad.tamu.edu\UgradUsers$\f0p1107\Home\MATLAB\class_interface_mex.cpp' failed.

Error using mex (line 206)
Unable to complete successfully.

Could anyone help me by letting me know how I can get rid of this error? I am no expert at coding so please try to keep your answer as simple as possible. Any help will be much appreciated.

Thank you!

[Richard Crozier]

Hmmm, the FEX comment box gobbled my libraries, it's the following two that I needed

cstring
typeinfo

[Richard Crozier]

I had to include both of the following to get it to compile on Linux

#include <cstring>
#include <typeinfo>

I'm using gcc 4.4.6. It ordered me to use typeinfo, I needed cstring to get strcmp.

Thanks for this though, it's incredibly useful to me!

[Gabri Gwala]

Thank you Andreas for you suggestion about compiling in Unix!!!

[Artem]

That's it, Oliver! Thanks a lot, a wonderful contribution!

[Oliver Woodford]

Artem: If you want to put this in a class directory then the mex file needs to go in a subdirectory of that folder called private.

[Artem]

Oliver, It is just 'mex class_interface_mex.cpp', right? It works fine if the mex-file is in a non-@ directory, but in the class dir it fails.

[Oliver Woodford]

Artem: Did you mex the file, as explained in the file description?

[Artem]

Great contribution!
I wonder if it is possible to put the class in @class_interface directory? In my case, Matlab cannot find class_interface_mex() function. Any suggestions?

[Andreas]

code needs some tweaking to compile on non-windows systems. What's the reason for using 'raw_name()' instead of 'name()'. The former is MS specific.

--- orig/class_handle.hpp 2012-11-08 15:34:08.000000000 +0100
+++ new/class_handle.hpp 2012-11-27 16:46:50.831263148 +0100
@@ -4,12 +4,28 @@
#include <stdint.h>
#include <string>

+#if !(defined _WIN32 || defined _WIN64) // needed to compile on linux.
+ #include <string.h>
+ #include <typeinfo>
+ #define raw_name name // it would be better to change the code so that we use 'name()' instead of 'raw_name()'
+#endif
+

--- orig/class_interface_mex.cpp 2012-11-08 16:10:26.000000000 +0100
+++ new/class_interface_mex.cpp 2012-11-27 16:46:47.375263270 +0100
@@ -1,6 +1,10 @@
#include "mex.h"
#include "class_handle.hpp"

+#if !(defined _WIN32 || defined _WIN64) // needed to compile on linux.
+ #include <string.h>
+#endif
+
// The class that we are interfacing to
class dummy
{

[Francesco Montorsi]

Works great! perfect to start interfacing C++ object-oriented code to MATLAB

[Matthew]

Great submission developed from an informative newsgroup thread (referred to in description).