reflection/runtime_component

• C

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  #include <runtime_component.h>
  #include <stdio.h>
   
  int main(int argc, char *argv[]) {
      ecs_world_t *ecs = ecs_init_w_args(argc, argv);
   
      // Create component for a type that isn't known at compile time
      ecs_entity_t Position = ecs_struct(ecs, {
          .members = {
              { .name = "x", .type = ecs_id(ecs_f32_t) }, // builtin float type
              { .name = "y", .type = ecs_id(ecs_f32_t) }
          }
      });
   
      // Create entity, set value of position using reflection API
      ecs_entity_t ent = ecs_entity(ecs, { .name = "ent" });
   
      // Get type info because we need to pass in the size
      const ecs_type_info_t *ti = ecs_get_type_info(ecs, Position);
      void *ptr = ecs_ensure_id(ecs, ent, Position, (size_t)ti->size);
   
      ecs_meta_cursor_t cur = ecs_meta_cursor(ecs, Position, ptr);
      ecs_meta_push(&cur);          // {
      ecs_meta_set_float(&cur, 10); //   10
      ecs_meta_next(&cur);          //   ,
      ecs_meta_set_float(&cur, 20); //   20
      ecs_meta_pop(&cur);           // }
   
      // Convert component to string
      char *str = ecs_ptr_to_expr(ecs, Position, ptr);
      printf("%s\n", str); // {x: 10, y: 20}
      ecs_os_free(str);
   
      ecs_fini(ecs);
  }

• C++

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  #include <runtime_component.h>
  #include <iostream>
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      // Create component for a type that isn't known at compile time
      flecs::entity position = ecs.component("Position")
          .member<float>("x")
          .member<float>("y");
   
      // Create entity, set value of position using reflection API
      flecs::entity e = ecs.entity();
      void *ptr = e.ensure(position);
   
      flecs::cursor cur = ecs.cursor(position, ptr);
      cur.push();
      cur.set_float(10);
      cur.next();
      cur.set_float(20);
      cur.pop();
   
      // Convert component to string
      std::cout << ecs.to_expr(position, ptr).c_str() << "\n"; // {x: 10, y: 20}
  }