66 lines
1.7 KiB
C++
66 lines
1.7 KiB
C++
#include <hierarchy.h>
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#include <iostream>
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struct Position {
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double x, y;
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};
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struct Star { };
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struct Planet { };
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struct Moon { };
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void iterate_tree(flecs::entity e, Position p_parent = {0, 0}) {
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// Print hierarchical name of entity & the entity type
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std::cout << e.path() << " [" << e.type().str() << "]\n";
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// Get entity position
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const Position *p = e.get<Position>();
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// Calculate actual position
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Position p_actual = {p->x + p_parent.x, p->y + p_parent.y};
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std::cout << "{" << p_actual.x << ", " << p_actual.y << "}\n\n";
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// Iterate children recursively
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e.children([&](flecs::entity child) {
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iterate_tree(child, p_actual);
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});
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}
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int main(int, char *[]) {
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flecs::world ecs;
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// Create a simple hierarchy.
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// Hierarchies use ECS relationships and the builtin flecs::ChildOf relationship to
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// create entities as children of other entities.
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flecs::entity sun = ecs.entity("Sun")
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.add<Star>()
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.set<Position>({1, 1});
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ecs.entity("Mercury")
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.child_of(sun) // Shortcut for add(flecs::ChildOf, sun)
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.add<Planet>()
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.set<Position>({1, 1});
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ecs.entity("Venus")
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.child_of(sun)
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.add<Planet>()
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.set<Position>({2, 2});
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flecs::entity earth = ecs.entity("Earth")
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.child_of(sun)
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.add<Planet>()
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.set<Position>({3, 3});
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flecs::entity moon = ecs.entity("Moon")
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.child_of(earth)
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.add<Moon>()
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.set<Position>({0.1, 0.1});
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// Is the Moon a child of Earth?
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std::cout << "Child of Earth? " << moon.has(flecs::ChildOf, earth) << "\n\n";
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// Do a depth-first walk of the tree
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iterate_tree(sun);
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}
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