This application is an example of how to create extensible applications using plugins in C++. This code is for teaching purposses.
The app calculates the area and perimeter of some figures. The necessary code for each figure is in a shared library in the plugins directory. The app tries to load every .so/.dll/.dylib file in that folder (unless some other folder were passed as argument) at runtime.
There are two important classes: plugin::Figure and plugin::FigureLoader. The first one is an abstract class that every plugin must be inherit from. The second one is loader and owner of each plugin, it uses the system API to load shared libraries at runtime.
This class has one field for the name of the figure and three pure virtual functions:
userInput(): It's used to initialize all required values to make the mathematics.area(): Calculates and returns the value of the area.perimeter(): Calculates and returns the value of the perimeter.
Also, for every derived class (plugin) must be a C function (figureFactory()),
that creates and returns a pointer to the derived class. There is the macro
(DEFAULT_FIGURE_FACTORY) that defines this function using the default
constructor of the class.
It encapsulates the functionality to load a dynamic library and create a
figure. It uses system APIs made in C and that's why the factory
function needs to be declared as C code (and because name mangling is simpler
than C++). The constructor loads the shared library using dlopen() or
LoadLibrary() function depending on the OS, searches the
factory function and calls it to create an instance of the plugin.
git clone https://github.com/reroman/CPP-PluginApp.git
cd CPP-PluginApp
cmake -B build .
cmake --build build
You can disable the build of plugins executing cmake as follows:
cmake -B build -DBUILD_PLUGINS=OFF .
... and create your own, just put the files in the plugins directory.
To execute:
cd build
./figures plugins
If you don't pass a folder name it will take plugins directory by default.
Ricardo Román. Email: reroman4@gmail.com.