Attrs example.

attrs.c

// https://gist.github.com/soasme/7ede641156d2a7bee4b8bec2e87c2197

#include <stdio.h>
#include "attrs.h"

AttrsError CoordinatePrint(AttrsArgs args) {
    AttrsRef self = AttrsGetSelf(args);
    
    FILE*    f    = AttrsGetPtrArg(args, "f", FILE*); // Or, FILE* f = (FILE*) AttrsGetPtr (AttrsGetArg(args, "f"));
    int      x    = AttrsGetInt(self, "x"); // Or, int x = AttrsGetInt(args, "self.x");
    int      y    = AttrsGetInt(self, "y"); // Or, int x = AttrsGetInt(args, "self.y");
    
    fprintf(f, "Coordinate(%u,%u)", x, y);
}

int main(int argc, char* argv[]) {
  // call before any Attrs function.
  AttrsInit();

  // make a class
  AttrsNewClass("Coordinate",
    "x = type: int, default: 0;"
    "y = type: int, default: 0;"
    "r = type: int, default: 1, private: true;"
    "o = type: Coordinate, private: true;"
    "def Print(f: File);"
  )

  // bind method
  AttrsDef("Coordinate:Print(f)", CoordinatePrint);

  // check a class.
  bool has_coordinate = AttrsGetFields("Coordinate");

  // inspect all fields.
  AttrsField* fields = AttrsGetFields("Coordinate");

  // check a field.
  bool has_a = AttrsHasField("Coordinate", "a");

  // inspect a field.
  AttrsField field = AttrsGetField("Coordinate", "a");

  // create a new object.
  AttrsRef c = AttrsCall("Coordinate:New(a, b)", 1, 2);

  // call a method.
  AttrsCall("Coordinate:Print(f)", c, AttrsBuiltin("stdout"));

  // call when Attrs is no longer used.
  AttrsDestroy();

  return 0;
}