queries/wildcards

• C

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  #include <wildcards.h>
  #include <stdio.h>
   
  // Queries can have wildcard terms that can match multiple instances of a
  // relationship or relationship target.
   
  typedef struct {
      int amount;
  } Eats;
   
  int main(int argc, char *argv[]) {
      ecs_world_t *ecs = ecs_init_w_args(argc, argv);
   
      ECS_COMPONENT(ecs, Eats);
      ECS_TAG(ecs, Apples);
      ECS_TAG(ecs, Pears);
   
      // Create a query that matches edible components
      ecs_query_t *q = ecs_query(ecs, {
          .terms = {{ .id = ecs_pair(ecs_id(Eats), EcsWildcard ) }}
      });
   
      // Create a few entities that match the query
      ecs_entity_t bob = ecs_entity(ecs, { .name = "Bob" });
      ecs_set_pair(ecs, bob, Eats, Apples, {10});
      ecs_set_pair(ecs, bob, Eats, Pears, {5});
   
      ecs_entity_t alice = ecs_entity(ecs, { .name = "Alice" });
      ecs_set_pair(ecs, alice, Eats, Apples, {4});
   
      // Iterate the query
      ecs_iter_t it = ecs_query_iter(ecs, q);
      while (ecs_query_next(&it)) {
          Eats *eats = ecs_field(&it, Eats, 0);
          ecs_id_t pair = ecs_field_id(&it, 0);
          ecs_entity_t food = ecs_pair_second(ecs, pair);
   
          for (int i = 0; i < it.count; i ++) {
              printf("%s eats %d %s\n", ecs_get_name(ecs, it.entities[i]),
                  eats[i].amount, ecs_get_name(ecs, food));
          }
      }
   
      // Output:
      //   Bob eats 10 Apples
      //   Bob eats 5 Pears
      //   Alice eats 4 Apples   
   
      return ecs_fini(ecs);
  }

• C++

  View on GitHub

  #include <wildcards.h>
  #include <iostream>
   
  // Queries can have wildcard terms that can match multiple instances of a
  // relationship or relationship target.
   
  struct Eats {
      int amount;
  };
   
  struct Apples { };
  struct Pears { };
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      // Create a query that matches edible components
      flecs::query<Eats> q = ecs.query_builder<Eats>()
          .term_at(0).second(flecs::Wildcard) // Change first argument to (Eats, *)
          .build();
   
      // Create a few entities that match the query
      ecs.entity("Bob")
          .set<Eats, Apples>({10})
          .set<Eats, Pears>({5});
   
      ecs.entity("Alice")
          .set<Eats, Apples>({4});
   
      // Iterate the query with a flecs::iter. This makes it possible to inspect
      // the pair that we are currently matched with.
      q.each([](flecs::iter& it, size_t index, Eats& eats) {
          flecs::entity e = it.entity(index);
          flecs::entity food = it.pair(0).second();
   
          std::cout << e.name() << " eats " 
              << eats.amount << " " << food.name() << std::endl;
      });
   
      // Output:
      //   Bob eats 10 Apples
      //   Bob eats 5 Pears
      //   Alice eats 4 Apples    
  }