entities/on_validate

• C

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  #include <on_validate.h>
  #include <stdio.h>
   
  // The on_validate hook is invoked when a component is set, before the on_set
  // hook and OnSet observers are invoked. When the hook returns false, the
  // on_set hook and OnSet observers are not invoked for the entity. This can be
  // used to guard application logic from invalid component values.
   
  typedef struct {
      double x, y;
  } Position;
   
  // Returns false when the position is outside of the world bounds.
  bool validate_position(ecs_world_t *world, ecs_entity_t e, void *ptr) {
      (void)world; (void)e;
      Position *p = ptr;
      return p->x >= 0 && p->x <= 100 && p->y >= 0 && p->y <= 100;
  }
   
  void on_set_position(ecs_iter_t *it) {
      Position *p = ecs_field(it, Position, 0);
   
      for (int i = 0; i < it->count; i ++) {
          printf("%s set to {%.0f, %.0f}\n",
              ecs_get_name(it->stage, it->entities[i]), p[i].x, p[i].y);
      }
  }
   
  int main(int argc, char *argv[]) {
      ecs_world_t *world = ecs_init_w_args(argc, argv);
   
      ECS_COMPONENT(world, Position);
   
      ecs_set_hooks(world, Position, {
          .on_validate = validate_position,
          .on_set = on_set_position
      });
   
      ecs_entity_t e = ecs_entity(world, { .name = "Entity" });
   
      // Position is inside world bounds, on_set is invoked
      ecs_set(world, e, Position, {50, 50});
   
      // Position is outside world bounds, on_set is not invoked
      ecs_set(world, e, Position, {150, 50});
   
      return ecs_fini(world);
   
      // Output:
      //   Entity set to {50, 50}
  }

• C++

  View on GitHub

  #include <on_validate.h>
  #include <iostream>
   
  // The on_validate hook is invoked when a component is set, before the on_set
  // hook and OnSet observers are invoked. When the hook returns false, the
  // on_set hook and OnSet observers are not invoked for the entity. This can be
  // used to guard application logic from invalid component values.
   
  struct Position {
      double x, y;
  };
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      ecs.component<Position>()
          // Returns false when the position is outside of the world bounds.
          .on_validate([](flecs::entity, Position& p) {
              return p.x >= 0 && p.x <= 100 && p.y >= 0 && p.y <= 100;
          })
          .on_set([](flecs::entity e, Position& p) {
              std::cout << e.name() << " set to {"
                  << p.x << ", " << p.y << "}" << std::endl;
          });
   
      flecs::entity e = ecs.entity("Entity");
   
      // Position is inside world bounds, on_set is invoked
      e.set<Position>({50, 50});
   
      // Position is outside world bounds, on_set is not invoked
      e.set<Position>({150, 50});
   
      // Output:
      //   Entity set to {50, 50}
  }