flecs - Iterate Relation Component C++ Example

main.cpp

#include "flecs.h"
#include <iostream>

struct Position {
	float x;
	float y;
};

struct Start {};
struct End {};

int main(int argc, char* argv[])
{
	flecs::world ecs{argc, argv};

	ecs.component<Position>();

	// Constrcut example entities
	ecs.entity("L1")
		.set<Position, Start>({ 0.f, 0.f })
		.set<Position, End>({ 1.f, 1.f });

	auto first = ecs.entity("first");
	auto second = ecs.entity("second");

	ecs.entity("L2")
		.set<Position>(first, { 0.f, 0.f })
		.set<Position>(second, { 1.f, 1.f });

	// Filter for entities
	std::cout << std::endl << "Filter Each Entity" << std::endl;
	ecs.filter_builder<>()
		.with<Position>(flecs::Any) // Find any entity with a (Position, ?) pair
		.each([](flecs::entity e) {
			std::cout << e.name() << std::endl;
			flecs::entity target;
			for (int index = 0; target = e.target<Position>(index); index++)
			{
				auto value = e.get<Position>(target);
				std::cout << target.name() << " = { x:" << value->x << ", y:" << value->y << " }" << std::endl;
			}
			std::cout << std::endl;
		});

	std::cout << "Filter Each Relation" << std::endl;
	ecs.filter_builder<>()
		.with<Position>(flecs::Wildcard) // Find all instances with a (Position, ?) pair
		.build()
		.iter([](flecs::iter& it) {
				auto column = it.field<Position>(1);
				for (auto i : it) {
					auto& value = column[i];
					std::cout << it.entity(i).name() << ", " << it.pair(1).second().name() << " = { x:" << value.x << ", y:" << value.y << " }" << std::endl;
				}
			});

	return 0;
}