gistfile1.m

int lmoaux_pushObjCRetValue(lua_State *L, NSInvocation *invocation) {
    void *ret;
    const char *pRetCode = [[invocation methodSignature] methodReturnType];
    switch (*pRetCode) {

        case '@':
            ret = malloc(sizeof(id)); [invocation getReturnValue:ret]; lua_pushlightuserdata(L, (id)*ret);
            break;
        case 'f':
            ret = malloc(sizeof(float)); [invocation getReturnValue:ret]; lua_pushnumber(L, (float)*ret);
            break;
        case 'i':
            ret = malloc(sizeof(int)); [invocation getReturnValue:ret]; lua_pushinteger(L, (int)*ret);
            break;
        case 'l':
            ret = malloc(sizeof(long)); [invocation getReturnValue:ret]; lua_pushnumber(L, (long)*ret);
            break;
        case 'd':
            ret = malloc(sizeof(double)); [invocation getReturnValue:ret]; lua_pushnumber(L, (double)*ret);
        default:
            break;
    }
}