Tiny Smalltalk-like objects in C.

tinySmalltalk.c

#include <stdio.h>
#include <stdlib.h>

typedef struct Object Object;

typedef struct MethodChain {
  const char* selector;
  Object* (*handler)(Object* self);
  struct MethodChain* next;
} MethodChain;

struct Object {
  MethodChain* methods;
};

Object* msg_send(Object* self, const char* selector) {
  if (!self) {
    printf("Error sending message %s.\n", selector);
  }

  MethodChain* currentMethod = self->methods;
  while (currentMethod && currentMethod->selector != selector) {
    currentMethod = currentMethod->next;
  }

  if (currentMethod && currentMethod->selector == selector) {
    return currentMethod->handler(self);
  } else {
    printf("Error sending message %s.\n", selector);
    return NULL;
  }
}

Object* greet(Object* self) {
  printf("Hello world!\n");
  return NULL;
}

int main() {
  const char* greetSelector = "greet";
  MethodChain transcriptMethodCheer = {0};
  transcriptMethodCheer.handler = greet;
  transcriptMethodCheer.selector = greetSelector;
  Object transcript = {0};
  transcript.methods = &transcriptMethodCheer;
  Object* Transcript = &transcript;

  msg_send(Transcript, greetSelector);
  return 0;
}