How to call a function within a class in legacy code tool structure?

Hello,

I do have a .cpp file that I want to integrate with Matlab through legacy code tool. My original code involves functions defined within a class, what is the proper way to write "def.OutputFcnSpec" command?

Answer 1

[Shantanu Dixit]

Hi Eiman,

To integrate a class method from a '.cpp' file with MATLAB using the 'Legacy Code Tool', you can create a wrapper function for the class method. This wrapper acts as an intermediary between MATLAB and the C++ class, allowing to reference it in the 'def.OutputFcnSpec' command.

Below is an example snippet for invoking C++ function using Legacy Code Tool:

Header File ("MyClass.h")

#ifndef _MYCLASS_H_
#define _MYCLASS_H_

class MyClass {
private:
    int state;
public:
    MyClass() : state(0) {}
    int increment(int val) { state += val; return state; }
};

extern MyClass* myInstance;

extern void createMyClass();   // Creates the instance
extern void deleteMyClass();   // Deletes the instance
extern int incrementWrapper(int val); // Wrapper for 'increment' method

#endif /* _MYCLASS_H_ */

Source File ("MyClass.cpp")

#include "MyClass.h"
MyClass* myInstance;

void createMyClass() { myInstance = new MyClass(); }
void deleteMyClass() { delete myInstance; }
int incrementWrapper(int val) { return myInstance->increment(val); }

MATLAB Legacy Code Tool usage

% Initialization
def = legacy_code('initialize');
def.SFunctionName = 'sfun_myclass';
def.StartFcnSpec = 'createMyClass()';

% Referencing the wrapper function
def.OutputFcnSpec = 'int32 y1 = incrementWrapper(int32 u1)';
def.TerminateFcnSpec = 'deleteMyClass()';
def.HeaderFiles = {'MyClass.h'};
def.SourceFiles = {'MyClass.cpp'};
def.Options.language = 'C++';

% Generate the S-Function for Simulink
legacy_code('generate_for_sim', def);

You can also refer to the useful MathWorks documentation on Integrating C/C++ code using Legacy Code Tool

• https://www.mathworks.com/help/simulink/sfg/integrating-existing-c-functions-into-simulink-models-with-the-legacy-code-tool.html
• https://www.mathworks.com/help/simulink/slref/c-object-methods-as-legacy-functions.html

Hope this helps!