queries/each_callback

• C++

  View on GitHub

  #include <each_callback.h>
  #include <iostream>
   
  // This example shows how to write a query with the each callback, which
  // provides the easiest API for iterating over matched components.
   
  struct Position { 
      double x, y;
  };
   
  struct Velocity { 
      double x, y;
  };
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      // Create a query for Position, Velocity.
      flecs::query<Position, const Velocity> q = 
          ecs.query<Position, const Velocity>();
   
      // Create a few test entities for a Position, Velocity query
      ecs.entity("e1")
          .set<Position>({10, 20})
          .set<Velocity>({1, 2});
   
      ecs.entity("e2")
          .set<Position>({10, 20})
          .set<Velocity>({3, 4});
   
      // This entity will not match as it does not have Position, Velocity
      ecs.entity("e3")
          .set<Position>({10, 20});
   
      // Arguments passed to each match query type
      q.each([](Position& p, const Velocity& v) {
          p.x += v.x;
          p.y += v.y;
          std::cout << "{" << p.x << ", " << p.y << "}\n";
      });
   
      // Output
      //  {11, 22}
      //  {13, 24}
  }