systems/each_w_iter_callback

• C++

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  #include <each_w_iter_callback.h>
  #include <iostream>
   
  // This example is the same as the each example, but in addition also shows how 
  // to get access to the flecs::iter object. Flecs iterators provide access to a
  // lot of information about the currently iterated result, such as the matched
  // entities, table, component ids, whether fields are set or not and more.
   
  struct Position { 
      double x, y;
  };
   
  struct Velocity { 
      double x, y;
  };
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      flecs::system s = ecs.system<Position, const Velocity>() 
          // Arguments passed to each match components passed to system
          .each([](flecs::iter& it, size_t row, Position& p, const Velocity& v) {
              flecs::entity e = it.entity(row);
              p.x += v.x;
              p.y += v.y;
              std::cout << e.name() << ": {" << p.x << ", " << p.y << "}\n";
          });
   
      // 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});
   
      // Run the system
      s.run();
   
      // Output
      //  e1: {11, 22}
      //  e2: {13, 24}
  }