queries/with

• C++

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  #include <with.h>
  #include <iostream>
   
  struct Position { 
      double x, y;
  };
   
  struct Npc { };
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      // Create a query for Position, Npc. By adding the Npc component using the
      // "with" method, the component is not a part of the query type, and as a
      // result does not become part of the function signatures of each and iter.
      // This is useful for things like tags, which because they don't have a 
      // value are less useful to pass to the each/iter functions as argument.
      flecs::query<Position> q = ecs.query_builder<Position>()
          .with<Npc>()
          .build();
   
      // Create a few test entities for the Position, Npc query
      ecs.entity("e1")
          .set<Position>({10, 20})
          .add<Npc>();
   
      ecs.entity("e2")
          .set<Position>({10, 20})
          .add<Npc>();
   
      // This entity will not match as it does not have Position, Npc
      ecs.entity("e3")
          .set<Position>({10, 20});
   
   
      // Note how the Npc tag is not part of the each signature
      q.each([](flecs::entity e, Position& p) {
          std::cout << e.name() << ": {" << p.x << ", " << p.y << "}\n";
      });
   
      // Output:
      //  e1: {10, 20}
      //  e2: {10, 20}
  }