entities/basics

• C

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  #include <basics.h>
  #include <stdio.h>
   
  typedef struct {
      double x, y;
  } Position;
   
  int main(int argc, char *argv[]) {
      ecs_world_t *ecs = ecs_init_w_args(argc, argv);
   
      ECS_COMPONENT(ecs, Position);
      ECS_TAG(ecs, Walking);
   
      // Create an entity with name Bob
      ecs_entity_t bob = ecs_set_name(ecs, 0, "Bob");
   
      // The set operation finds or creates a component, and sets it.
      ecs_set(ecs, bob, Position, {10, 20});
      // The add operation adds a component without setting a value. This is
      // useful for tags, or when adding a component with its default value.    
      ecs_add(ecs, bob, Walking);
   
      // Get the value for the Position component
      const Position *ptr = ecs_get(ecs, bob, Position);
      printf("{%f, %f}\n", ptr->x, ptr->y);
   
      // Overwrite the value of the Position component
      ecs_set(ecs, bob, Position, {20, 30});
   
      // Create another named entity
      ecs_entity_t alice = ecs_set_name(ecs, 0, "Alice");
      ecs_set(ecs, alice, Position, {10, 20});
      ecs_add(ecs, alice, Walking);
   
      // Print all the components the entity has. This will output:
      //    Position, Walking, (Identifier,Name)
      char *str = ecs_type_str(ecs, ecs_get_type(ecs, alice));
      printf("[%s]\n", str);
      ecs_os_free(str);
   
      // Remove tag
      ecs_remove(ecs, alice, Walking);
   
      // Iterate all entities with Position
      ecs_iter_t it = ecs_each(ecs, Position);
      while (ecs_each_next(&it)) {
          Position *p = ecs_field(&it, Position, 0);
          for (int i = 0; i < it.count; i ++) {
              printf("%s: {%f, %f}\n", ecs_get_name(ecs, it.entities[i]),
                  p[i].x, p[i].y);
          }
      }
   
      return ecs_fini(ecs);
   
      // Output
      //  {10.000000, 20.000000}
      //  [Position, Walking, (Identifier,Name)]
      //  Alice: {10.000000, 20.000000}
      //  Bob: {20.000000, 30.000000}
  }

• C++

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  #include <basics.h>
  #include <iostream>
   
  struct Position {
      double x, y;
  };
   
  struct Walking { };
   
  int main(int, char *[]) {
      flecs::world ecs;
   
      // Create an entity with name Bob
      flecs::entity bob = ecs.entity("Bob")
          // The set operation finds or creates a component, and sets it.
          // Components are automatically registered with the world.
          .set<Position>({10, 20}) 
          // The add operation adds a component without setting a value. This is
          // useful for tags, or when adding a component with its default value.
          .add<Walking>();
   
      // Get the value for the Position component
      const Position& c = bob.get<Position>();
      std::cout << "{" << c.x << ", " << c.y << "}" << "\n";
   
      // Overwrite the value of the Position component
      bob.set<Position>({20, 30});
   
      // Create another named entity
      flecs::entity alice = ecs.entity("Alice")
          .set<Position>({10, 20});
   
      // Add a tag after entity is created
      alice.add<Walking>();
   
      // Print all of the components the entity has. This will output:
      //    Position, Walking, (Identifier,Name)
      std::cout << "[" << alice.type().str() << "]" << "\n";
   
      // Remove tag
      alice.remove<Walking>();
   
      // Iterate all entities with Position
      ecs.each([](flecs::entity e, Position& p) {
          std::cout << e.name() << ": {" << p.x << ", " << p.y << "}" << "\n";
      });
   
      // Output
      //  {10, 20}
      //  [Position, Walking, (Identifier,Name)]
      //  Alice: {10, 20}
      //  Bob: {20, 30}
  }