queries/iter_targets

• C

  View on GitHub

  #include <iter_targets.h>
  #include <stdio.h>
   
  // This example shows how to iterate matching targets of a relationship without
  // iterating the same entity multiple times.
  //
  // When creating a (Relationship, *) query, the query will return one result per
  // matching relationship pair, which returns the same entity multiple times. 
  // This example uses a (Relationship, _) query which at most returns a single
  // result per matching pair, and the returned table record to iterate the
  // targets for the current result.
   
  int main(int argc, char *argv[]) {
      ecs_world_t *ecs = ecs_init_w_args(argc, argv);
   
      ECS_TAG(ecs, Eats);
      ECS_TAG(ecs, Pizza);
      ECS_TAG(ecs, Salad);
   
      ecs_entity_t bob = ecs_entity(ecs, { .name = "Bob" });
      ecs_add_pair(ecs, bob, Eats, Pizza);
      ecs_add_pair(ecs, bob, Eats, Salad);
   
      ecs_query_t *q = ecs_query(ecs, {
          // EcsAny ensures that only a single result is returned per entity, as 
          // opposed to EcsWildcard which returns a result per matched pair.
          .terms = {{ .id = ecs_pair(Eats, EcsAny) }}
      });
      
      ecs_iter_t it = ecs_query_iter(ecs, q);
      while (ecs_query_next(&it)) {
          const ecs_type_t *type = ecs_table_get_type(it.table);
          const ecs_table_record_t *tr = it.trs[0];
   
          for (int i = 0; i < it.count; i ++) {
              printf("%s eats:\n", ecs_get_name(ecs, it.entities[i]));
              for (int t = 0; t < tr->count; t ++) {
                  ecs_entity_t tgt = ecs_pair_second(
                      ecs, type->array[t + tr->index]);
                  printf(" - %s\n", ecs_get_name(ecs, tgt));
              }
          }
      }
   
      return ecs_fini(ecs);
   
      // Output:
      //  Bob eats: 
      //   - Pizza
      //   - Salad
  }

• C++

  View on GitHub

  #include <iter_targets.h>
  #include <iostream>
   
  // This example shows how to iterate matching targets of a relationship without
  // iterating the same entity multiple times.
  //
  // When creating a (Relationship, *) query, the query will return one result per
  // matching relationship pair, which returns the same entity multiple times. 
  // This example uses a (Relationship, _) query which at most returns a single
  // result per matching pair, and a targets() function that iterates the targets
  // for the current entity.
   
  struct Eats { };
  struct Pizza { };
  struct Salad { };
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      ecs.entity("Bob")
          .add<Eats, Pizza>()
          .add<Eats, Salad>();
   
      ecs.query_builder()
          .with<Eats>(flecs::Any) // flecs::Any ensures that only a single result
                                  // is returned per entity, as opposed to 
                                  // flecs::Wildcard which returns a result per
                                  // matched pair.
   
          .each([](flecs::iter& it, size_t row) {
              flecs::entity e = it.entity(row);
              std::cout << e.name() << " eats: \n";
   
              it.targets(0, [](flecs::entity tgt) {
                  std::cout << " - " << tgt.name() << "\n";
              });
          });
   
      // Output:
      //  Bob eats: 
      //   - Pizza
      //   - Salad
  }