57 lines
2.0 KiB
C++
57 lines
2.0 KiB
C++
#include <basics.h>
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#include <iostream>
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// Prefabs are entities that can be used as templates for other entities. They
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// are created with a builtin Prefab tag, which by default excludes them from
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// queries and systems.
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//
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// Prefab instances are entities that have an IsA relationship to the prefab.
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// The IsA relationship causes instances to inherit the components from the
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// prefab. By default all instances for a prefab share its components.
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//
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// Inherited components save memory as they only need to be stored once for all
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// prefab instances. They also speed up the creation of prefabs, as inherited
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// components don't need to be copied to the instances.
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//
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// To get a private copy of a component, an instance can add it which is called
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// an override. Overrides can be manual (by using add) or automatic (see the
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// auto_override example).
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//
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// If a prefab has children, adding the IsA relationship instantiates the prefab
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// children for the instance (see hierarchy example).
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struct Defense {
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double value;
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};
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int main() {
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flecs::world ecs;
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// Create a SpaceShip prefab with a Defense component.
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flecs::entity SpaceShip = ecs.prefab("SpaceShip")
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.set<Defense>({ 50 });
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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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// Because of the IsA relationship, the instance now shares the Defense
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// component with the prefab, and can be retrieved as a regular component:
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const Defense *d_inst = inst.get<Defense>();
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std::cout << "defense: " << d_inst->value << "\n";
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// Because the component is shared, changing the value on the prefab will
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// also change the value for the instance:
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SpaceShip.set<Defense>({ 100 });
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std::cout << "defense after set: " << d_inst->value << "\n";
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// Prefab components can be iterated like regular components:
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ecs.each([](flecs::entity e, Defense& d) {
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std::cout << e.path() << ": " << d.value << "\n";
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});
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// Output:
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// defense: 50
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// defense after set: 100
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// ::my_spaceship: 100
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}
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