Create C++ MATLAB Data API Shared Library Header from Strongly Typed MATLAB Classes Contained in Package

This example shows how to create a C++ shared library header from strongly typed MATLAB^® classes contained within a package and integrate it with sample C++ application code.

Prerequisites

• Start this example by creating a new work folder that is visible to the MATLAB search path.

• Verify that you have a C++ compiler installed by typing mbuild -setup at the MATLAB command prompt.

• End users must have an installation of MATLAB Runtime to run the application. For details, see Install and Configure MATLAB Runtime.

  For testing purposes, you can use an installation of MATLAB instead of MATLAB Runtime.

Files

Location of Example Files

Example Files

matlabroot\extern\examples\compilersdk\c_cpp\strongly_typed

Purpose of Each Example File

Files	Purpose
+shapes	Package containing two classes: MyPosition.m and MyRectangle.m
MyPosition.m	A class within the +shapes package that accepts the X and Y coordinates of a point and creates a MyPosition object
MyRectangle.m	A class within the +shapes package that accepts two points specified as MyPosition objects and creates a MyRectangle object
calculatearea.m	A function that accepts a MyRectangle object as input and calculates the area of the rectangle
shapes_mda.cpp	C++ application code that integrates the header file generated by compiling the MATLAB code

Copy the example files to the current work folder.

appDir = fullfile(matlabroot,'extern','examples','compilersdk','c_cpp','strongly_typed');
copyfile(appDir)

Create Classes and Functions in MATLAB

1. Examine the code for MyPosition.m, MyRectangle.m, and calculatearea.m.

   • The +shapes package contains two MATLAB classes: MyPosition.m and MyRectangle.m.

   • The calculatearea.m MATLAB function located outside of the +shapes package accepts a MyRectangle object as input and calculates the area of the rectangle.

2. Create a MATLAB script named runshapes.m with the following code and execute it at the MATLAB command prompt. This script illustrates how the classes and function interact to generate an output.

    runshapes.m

   % Import shapes package
   import shapes.*;
   
   %% Create Rectangle 1 
   % Create MyPosition object for point 1
   p1 = MyPosition; 
   p1.X = 10;
   p1.Y = 5;
   % Create MyPosition object for point 2
   p2 = MyPosition; 
   p2.X = 50;
   p2.Y = 20;
   % Create MyRectangle object
   r1 = MyRectangle; 
   r1.UpperLeft = p1;
   r1.LowerRight = p2;
   % Calculate area of rectangle 1
   a1 = calculatearea(r1);
   % Display rectangle 1 info
   disp('Rectangle 1')
   disp(['Point 1 = ' '(' num2str(p1.X,'%.6f'), ',' num2str(p1.Y,'%.6f') ')'])
   disp(['Point 2 = ' '(' num2str(p2.X,'%.6f'), ',' num2str(p2.Y,'%.6f') ')'])
   disp(['Rectangle ' '(' num2str(p1.X,'%.6f'), ',' num2str(p1.Y,'%.6f') ')',...
       ' -> ' '(' num2str(p2.X,'%.6f'), ',' num2str(p2.Y,'%.6f') ')'])
   
   %% Create Rectangle 2 
   % Create rectangle 2 by enlarging rectangle 1
   r2 = r1.enlarge(10);
   % Get positions of rectnagle 2
   q1 = r2.UpperLeft();
   q2 = r2.LowerRight();
   % Calculate area of rectangle 2
   a2 = calculatearea(r2);
   % Display rectangle 2 info
   disp('Rectangle 2')
   disp(['Point 1 = ' '(' num2str(q1.X,'%.6f'), ',' num2str(q1.Y,'%.6f') ')'])
   disp(['Point 2 = ' '(' num2str(q2.X,'%.6f'), ',' num2str(q2.Y,'%.6f') ')'])
   disp(['Rectangle ' '(' num2str(q1.X,'%.6f'), ',' num2str(q1.Y,'%.6f') ')',...
       ' -> ' '(' num2str(q2.X,'%.6f'), ',' num2str(q2.Y,'%.6f') ')'])
   
   %% Display the area of the two rectangles
   disp(['Area of rectangle r1 = ' num2str(a1)])
   disp(['Area of rectangle r2 = ' num2str(a2)])

   runshapes

   Rectangle 1
   Point 1 = (10.000000,5.000000)
   Point 2 = (50.000000,20.000000)
   Rectangle (10.000000,5.000000) -> (50.000000,20.000000)
   Rectangle 2
   Point 1 = (0.000000,-5.000000)
   Point 2 = (60.000000,30.000000)
   Rectangle (0.000000,-5.000000) -> (60.000000,30.000000)
   Area of rectangle r1 = 600
   Area of rectangle r2 = 2100

Generate C++ Shared Library Header Using the mcc Command

if ~exist('output/cpp','dir')
    mkdir output/cpp
end
mcc -W 'cpplib:libshapes,generic' +shapes/MyPosition.m +shapes/MyRectangle.m calculatearea.m -d output/cpp

The following files are created in the output>cpp>v2>generic_interface folder:

• readme.txt

• libshapes.ctf

• libshapesv2.hpp

For details, see Data Type Mappings Between C++ and Strongly Typed MATLAB Code.

 libshapesv2.hpp

#include "MatlabTypesInterface.hpp"

namespace shapes {
    class MyPosition : public MATLABObject<MATLABControllerType> { 
    public:

        // constructors
        MyPosition() : MATLABObject() {}

        MyPosition(std::shared_ptr<MATLABControllerType> matlabPtr) :
            MATLABObject(matlabPtr, u"shapes.MyPosition")
        {}

        MyPosition(std::shared_ptr<MATLABControllerType> matlabPtr, matlab::data::Array obj) :
            MATLABObject(matlabPtr, obj)
        {}

        // properties
        double getX() { return MATLABGetScalarProperty<double>(u"X"); }
        void setX(double value) { return MATLABSetScalarProperty(u"X", value); }
        double getY() { return MATLABGetScalarProperty<double>(u"Y"); }
        void setY(double value) { return MATLABSetScalarProperty(u"Y", value); }

        // methods
    };
}

namespace shapes {
    class MyRectangle : public MATLABObject<MATLABControllerType> { 
    public:

        // constructors
        MyRectangle() : MATLABObject() {}

        MyRectangle(std::shared_ptr<MATLABControllerType> matlabPtr) :
            MATLABObject(matlabPtr, u"shapes.MyRectangle")
        {}

        MyRectangle(std::shared_ptr<MATLABControllerType> matlabPtr, matlab::data::Array obj) :
            MATLABObject(matlabPtr, obj)
        {}

        // properties
        shapes::MyPosition getUpperLeft() {
            matlab::data::Array obj = MATLABGetScalarProperty<matlab::data::Array>(u"UpperLeft");
            return shapes::MyPosition(m_matlabPtr, obj);
        }
        void setUpperLeft(shapes::MyPosition obj) {
            MATLABSetScalarProperty(u"UpperLeft", matlab::data::Array(obj));
        }
        shapes::MyPosition getLowerRight() {
            matlab::data::Array obj = MATLABGetScalarProperty<matlab::data::Array>(u"LowerRight");
            return shapes::MyPosition(m_matlabPtr, obj);
        }
        void setLowerRight(shapes::MyPosition obj) {
            MATLABSetScalarProperty(u"LowerRight", matlab::data::Array(obj));
        }

        // methods
        matlab::data::Array show() { 
            matlab::data::ArrayFactory _arrayFactory;
            std::vector<matlab::data::Array> _args = {
                m_object };
            matlab::data::Array _result = MATLABCallOneOutputMethod(u"show", _args);
            return _result;
        }

        matlab::data::Array enlarge(double n) { 
            matlab::data::ArrayFactory _arrayFactory;
            matlab::data::ArrayDimensions _dims1 = {1, 1};
            std::vector<matlab::data::Array> _args = {
                m_object,
                _arrayFactory.createArray<double>(_dims1, {n}) };
            matlab::data::Array _result = MATLABCallOneOutputMethod(u"enlarge", _args);
            return _result;
        }

    };
}

matlab::data::Array calculatearea(std::shared_ptr<MATLABControllerType> _matlabPtr, shapes::MyRectangle rect) { 
    matlab::data::ArrayFactory _arrayFactory;
    matlab::data::ArrayDimensions _dims1 = {1, 1};
    std::vector<matlab::data::Array> _args = {
        rect };
    matlab::data::Array _result = _matlabPtr->feval(u"calculatearea", _args);
    return _result;
}

Integrate C++ MATLAB Data API Shared Library Header with C++ Application

1. Examine the C++ application code contained in the shapes_mda.cpp file.

   Note

   When writing C++ application code, you must include the header file (.hpp file) generated by the mcc command or the Library Compiler app and the MatlabCppSharedLib.hpp header file using #include directives.

2. Compile and link the C++ application at the MATLAB command prompt.

   mbuild shapes_mda.cpp -outdir output/cpp

3. Run the application from the system command prompt by passing the deployable archive (.ctf file) as an input. Before running the application at the system command prompt, verify that you have MATLAB Runtime installed on your machine prior to running the application at the system command prompt. For details, see Install and Configure MATLAB Runtime.

   For testing purposes, you can run the application from the MATLAB command prompt.

   !output\cpp\shapes_mda.exe output\cpp\v2\generic_interface\libshapes.ctf

   Rectangle 1  
   Point (10.000000, 5.000000) 
   Point (50.000000, 20.000000) 
   Rectangle (10.000000, 5.000000) -> (50.000000, 20.000000) 
   Rectangle 2  
   Point (0.000000, -5.000000) 
   Point (60.000000, 30.000000) 
   Rectangle (0.000000, -5.000000) -> (60.000000, 30.000000) 
   Area of rectangle r1 = 600 
   Area of rectangle r2 = 2100