script/functions

• C

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  #include <functions.h>
  #include <stdio.h>
   
  /* This example shows how to use user-defined functions in scripts. */
   
  const char *code = 
      "e {\n"
      "  Position: { sum(10, 20), (30).add(40) }\n"
      "}\n"
      ;
   
  typedef struct {
      int32_t x, y;
  } Position;
   
  void sum(
      const ecs_function_ctx_t *ctx,
      int argc,
      const ecs_value_t *argv,
      ecs_value_t *result)
  {
      (void)ctx;
      (void)argc;
   
      *(int64_t*)result->ptr = 
          *(int64_t*)argv[0].ptr +
          *(int64_t*)argv[1].ptr;
  }
   
  int main(int argc, char *argv[]) {
      ecs_world_t *world = ecs_init_w_args(argc, argv);
   
      ECS_COMPONENT(world, Position);
   
      // Add reflection data to component so we can assign it in script
      ecs_struct(world, {
          .entity = ecs_id(Position), // Make sure to use existing id
          .members = {
              { .name = "x", .type = ecs_id(ecs_i32_t) },
              { .name = "y", .type = ecs_id(ecs_i32_t) }
          }
      });
   
      // Define a sum function
      ecs_function(world, {
          .name = "sum",
          .return_type = ecs_id(ecs_i64_t),
          .params = {
              { .name = "a", .type = ecs_id(ecs_i64_t) },
              { .name = "b", .type = ecs_id(ecs_i64_t) }
          },
          .callback = sum
      });
   
      // Define an add method. A method is like a function, except that it can be
      // called on type instances, and receives the instance as first parameter.
      ecs_method(world, {
          .name = "add",
          .parent = ecs_id(ecs_i64_t), // Add method to i64
          .return_type = ecs_id(ecs_i64_t),
          .params = {
              { .name = "a", .type = ecs_id(ecs_i64_t) }
          },
          .callback = sum
      });
   
      if (ecs_script_run(world, "My script", code, NULL)) {
          printf("script failed to run\n");
          return -1;
      }
   
      // Get entity and Position component
      ecs_entity_t e = ecs_lookup(world, "e");
      const Position *p = ecs_get(world, e, Position);
   
      printf("{x: %d, y: %d}\n", p->x, p->y);
   
      return ecs_fini(world);
   
      // Output
      //  {30, 70}
  }