Object Oriented Problem

Start simple. A record in pascal is a lot like a class. But a class has the functions that work on the class'es data fields. This is where to start -- a simple class with a few functions that is much like your modular programming. Work that up and slowly add things -- overload an operator, add a static variable, inherit (derive) a class from another. The more complex OOP stuff can be shelved for quite some time until the simpler stuff makes sense. Study classes before templates -- all the way thru the harder OOP concepts -- templates really require a good OOP knowledge.

Here's a pared down example of the things I mentioned in my earlier post.

The program reads an XML file specified on the command line and writes it as UTF-8 to standard output.

First we have a very basic wrapper class around a C library, Expat.

#ifndef WRAP_EXPAT_H
#define WRAP_EXPAT_H

#include <expat.h>
#include <string>
#include <vector>

class WrapExpat
{
public:
WrapExpat(bool nameSpaceAware = false);
virtual ~WrapExpat();
bool parse(const string& buffer);
std::string getLastError();
protected:
XML_Parser p;
};

#endif

Next we have a class derived from WrapExpat, XmlUtf8Reader, that stores the XML in a std::string object.

#ifndef XML_UTF_READER_H
#define XML_UTF_READER_H

#include <string>
#include "wrapexpat.h"

class XmlUtf8Reader : public WrapExpat
{
public:
XmlUtf8Reader(bool parseDeclaration = true, size_t size = BUFSIZ);
virtual ~XmlUtf8Reader();
std::string getBuffer();
private:
std::string buffer;
static void XMLCALL xmldeclhandler(
void *data,
const XML_Char *version,
const XML_Char *encoding,
int standalone);
static void XMLCALL defaulthandler(
void *data,
const XML_Char *s,
int len);
};

#endif

With these two classes in place, we can write the following miniature application:

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <memory>
#include "xmlutf8reader.h"

int main(int argc, char *argv[])
{
if (argc < 2)
{
std::cerr << "Usage: myprog <input file>" << std::endl;
return 1;
}
std::ifstream ifs(*(++argv));
if (!ifs)
{
return 2;
}
std::stringstream iss;
iss << ifs.rdbuf();
std::string buffer(iss.str());

std::auto_ptr<XmlUtf8Reader> reader(new XmlUtf8Reader());
if (!reader->parse(buffer))
{
std::cerr << reader->getLastError();
return 3;
}
std::cout << reader->getBuffer();
return 0;
}

Is this the kind of thing you have in mind?

If you're looking for step by step instructions, a tutorial would be a good place to start. The Wikipedia article on C++ (http://en.wikipedia.org/wiki/C_Plus_Plus) lists some of them.

What I would say, though, is that it's much more fun to start with a problem you want to solve. Perhaps a program that reads a *.wav file and saves a copy that runs twice as fast? (That's the example I meant to post but I don't have access to the files at the moment.) There are so many useful things one can write there really is no need to create a class Person, then a derived class Employee, then FullTimeEmployee and PartTimeEmployee, etc.