posts: multiple-dispatch: add 'yomm2' example

This commit is contained in:
Bruno BELANYI 2022-11-03 11:22:24 +01:00
parent 245d7d123d
commit bd5f947469

View file

@ -290,3 +290,40 @@ In the meantime, one can find some libraries (like [`yomm2`][yomm2]) that
reduce the amount of boiler-plate needed to emulate this feature. reduce the amount of boiler-plate needed to emulate this feature.
[yomm2]: https://github.com/jll63/yomm2 [yomm2]: https://github.com/jll63/yomm2
```cpp
#include <yorel/yomm2/keywords.hpp>
struct SpaceObject {
virtual ~SpaceObject() = default;
};
struct Asteroid : SpaceObject { /* fields, methods, etc... */ };
struct Spaceship : SpaceObject { /* fields, methods, etc... */ };
// Register all sub-classes of `SpaceObject` for use with open methods
register_classes(SpaceObject, Asteroid, Spaceship);
// Register the `collide` open method, which dispatches on two arguments
declare_method(void, collide, (virtual_<SpaceObject&>, virtual_<SpaceObject&>));
// Write the different implementations of `collide`
define_method(void, collide, (Asteroid& left, Asteroid& right)) { /* work */ }
define_method(void, collide, (Asteroid& left, Spaceship& right)) { /* work */ }
define_method(void, collide, (Spaceship& left, Asteroid& right)) { /* work */ }
define_method(void, collide, (Spaceship& left, Spaceship& right)) { /* work */ }
int main() {
yorel::yomm2::update_methods();
auto asteroid = std::make_unique<Asteroid>();
auto spaceship = std::make_unique<Spaceship>();
collide(*asteroid, *spaceship); // Calls (Asteroid, Spaceship) version
collide(*spaceship, *asteroid); // Calls (Spaceship, Asteroid) version
collide(*asteroid, *asteroid); // Calls (Asteroid, Asteroid) version
collide(*spaceship, *spaceship); // Calls (Spaceship, Spaceship) version
}
```