66 lines
2.6 KiB
C++
66 lines
2.6 KiB
C++
#include <slots.h>
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#include <iostream>
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// Slots can be combined with prefab hierarchies to make it easier to access
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// the child entities created for an instance.
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//
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// To create a slot, the SlotOf relationship is added to the child of a prefab,
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// with as relationship target the prefab for which to register the slot. When
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// the prefab is instantiated, each slot will be added as a relationship pair
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// to the instance that looks like this:
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// (PrefabChild, InstanceChild)
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//
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// For a SpaceShip prefab and an Engine child, that pair would look like this:
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// (SpaceShip.Engine, Instance.Engine)
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//
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// To get the entity for a slot, an application can use the regular functions
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// to inspect relationships and relationship targets (see code).
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//
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// Slots can be added to any level of a prefab hierarchy, as long as it is above
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// (a parent of) the slot itself. When the prefab tree is instantiated, the
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// slots are added to the entities that correspond with the prefab children.
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//
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// Without slots, an application would have to rely on manually looking up
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// entities by name to get access to the instantiated children, like what the
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// hierarchy example does.
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int main() {
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flecs::world ecs;
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// Create the same prefab hierarchy as from the hierarchy example, but now
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// with the SlotOf relationship.
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flecs::entity SpaceShip = ecs.prefab("SpaceShip");
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flecs::entity Engine = ecs.prefab("Engine")
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.child_of(SpaceShip)
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.slot_of(SpaceShip);
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flecs::entity Cockpit = ecs.prefab("Cockpit")
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.child_of(SpaceShip)
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.slot_of(SpaceShip);
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// Add an additional child to the Cockpit prefab to demonstrate how
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// slots can be different from the parent. This slot could have been
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// added to the Cockpit prefab, but instead we register it on the top
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// level SpaceShip prefab.
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flecs::entity PilotSeat = ecs.prefab("PilotSeat")
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.child_of(Cockpit)
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.slot_of(SpaceShip);
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// Create a prefab instance.
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flecs::entity inst = ecs.entity("my_spaceship").is_a(SpaceShip);
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// Get the instantiated entities for the prefab slots
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flecs::entity inst_engine = inst.target(Engine);
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flecs::entity inst_cockpit = inst.target(Cockpit);
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flecs::entity inst_seat = inst.target(PilotSeat);
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std::cout << "instance engine: " << inst_engine.path() << "\n";
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std::cout << "instance cockpit: " << inst_cockpit.path() << "\n";
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std::cout << "instance seat: " << inst_seat.path() << "\n";
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// Output:
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// instance engine: ::my_spaceship::Engine
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// instance cockpit: ::my_spaceship::Cockpit
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// instance seat: ::my_spaceship::Cockpit::PilotSeat
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}
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