Should an object write itself out to a file, or should another object act on it to perform I/O?

Question

NOTE: Sorry for the long question!

I\'m trying to understand some key areas behind object orientation and I couldn\'t decide one way or another about my par

Answer 1

Do this:

public interface Writable {
    public void Save(Writer w);
}

public interface Writer {
    public void WriteTag(String tag, String cdata);
}

public class Bob : Writable {
    private String ssn = "123-23-1234";
    public void Save(Writer w) {
        w.WriteTag("ssn", ssn);
    }
}

public class XmlWriter : Writer {
    public XmlWriter(Sting filename) {...}
    public void WriteTag(String tag, Sting cdata) {...}
}

Obviously this isn't a complete solution but you should get the general idea.