reflection/units

• C

  View on GitHub

  #include <units.h>
  #include <stdio.h>
   
  typedef struct {
      double temperature;
      double pressure;
      double precipitation;
  } WeatherStation;
   
  void print_value(ecs_world_t *world, const ecs_meta_cursor_t *cur) {
      // Get unit entity and component
      ecs_entity_t u = ecs_meta_get_unit(cur);
      const EcsUnit *u_data = ecs_get(world, u, EcsUnit);
      
      // Print value with unit symbol
      printf("%s: %.1f %s\n", ecs_meta_get_member(cur), ecs_meta_get_float(cur),
          u_data->symbol);
  }
   
  int main(int argc, char *argv[]) {
      ecs_world_t *ecs = ecs_init_w_args(argc, argv);
   
      // Import units module.
      ECS_IMPORT(ecs, FlecsUnits);
   
      ECS_COMPONENT(ecs, WeatherStation);
   
      // Register reflection data with units. This can improve the way information
      // is visualized in tools, such as the explorer.
      ecs_struct(ecs, {
          .entity = ecs_id(WeatherStation),
          .members = {
              {
                  .name = "temperature", 
                  .type = ecs_id(ecs_f64_t), 
                  .unit = EcsCelsius 
              },
              { 
                  .name = "pressure", 
                  .type = ecs_id(ecs_f64_t), 
                  .unit = EcsBar 
              },
              {
                  .name = "precipitation", 
                  .type = ecs_id(ecs_f64_t), 
                  .unit = EcsMilliMeters 
              },
          }
      });
   
      ecs_entity_t e = ecs_insert(ecs, ecs_value(WeatherStation, {24, 1.2, 0.5}));
   
      // Use cursor API to print values with units
      WeatherStation *ptr = ecs_ensure(ecs, e, WeatherStation);
      ecs_meta_cursor_t cur = ecs_meta_cursor(ecs, ecs_id(WeatherStation), ptr);
   
      ecs_meta_push(&cur);
      print_value(ecs, &cur);
      ecs_meta_next(&cur);
      print_value(ecs, &cur);
      ecs_meta_next(&cur);
      print_value(ecs, &cur);
      ecs_meta_pop(&cur);
   
      return ecs_fini(ecs);
   
      // Output:
      //  temperature: 24.0 °C
      //  pressure: 1.2 bar
      //  precipitation: 0.5 mm
  }

• C++

  View on GitHub

  #include <units.h>
  #include <iostream>
   
  struct WeatherStation {
      double temperature;
      double pressure;
      double precipitation;
  };
   
  void print_value(const flecs::cursor& cur) {
      // Get unit entity and component
      flecs::entity u = cur.get_unit();
      const flecs::Unit& u_data = u.get<flecs::Unit>();
   
      // Print value with unit symbol
      std::cout << cur.get_member() << ": " << cur.get_float() 
          << " " << u_data.symbol << "\n";
  }
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      // Import units module.
      ecs.import<flecs::units>();
   
      // Register reflection data with units. This can improve the way information
      // is visualized in tools, such as the explorer.
      ecs.component<WeatherStation>()
          .member<double, flecs::units::temperature::Celsius>("temperature")
          .member<double, flecs::units::pressure::Bar>("pressure")
          .member<double, flecs::units::length::MilliMeters>("precipitation");
   
      flecs::entity e = ecs.entity().set<WeatherStation>({24, 1.2, 0.5});
   
      // Use cursor API to print values with units
      WeatherStation& ptr = e.ensure<WeatherStation>();
      flecs::cursor cur = ecs.cursor<WeatherStation>(&ptr);
      cur.push();
      print_value(cur);
      cur.next();
      print_value(cur);
      cur.next();
      print_value(cur);
      cur.pop();
   
      // Output:
      //  temperature: 24 °C
      //  pressure: 1.2 bar
      //  precipitation: 0.5 mm
  }