Design pattern for multiple output formats

Question

I have a class structure which represents (internally) the data I wish to output to a file.

Some of the member variables are private to the data class so that it can manage itself and stop things going awry.

I then want this data to be output into a number of file formats. I could do something like

savefile_formatA(DataClass* pDataClass, ofstream& fout);
savefile_formatB(DataClass* pDataClass, ofstream& fout);

except that the functions need to then see the private member variables of DataClass. I could of course just make savefile_formatXYZ() friend functions but then I would need to add a friend declaration for every different format.

Is there a standard design pattern for solving this kind of thing? How would you solve this problem?

Thanks!

Answer 1

I think the problem you have here is one of design. Serializing to a file shouldn't be modifying that data in anyway, so why should those functions be private? If all you are doing is examining data and writing it out, you should have an adequate public interface.