Howdy, Monks.

I'm in the process of putting together a couple of OO-based modules that wrap binaries and perform various sorts, subsets and munging operations on files.

The main problem I have is tracking all the files produced by each operation, and using that information to cut back on the amount of the information required by each method call.

In my quest to simplify (at least to the caller) the amount of parameters required I've tried the following:

• Track the last file or files produced, and various bits of data relating to those files.
  Assume that the last file produced is the one to operate on for the next operation, unless told otherwise.

This breaks very quickly - the user might do things in a valid but wierd order, or the code will pick the wrong file.

• Return the filenames of the output and ask for input filenames

Also not great - then we have to repeatedly recalculate supplimentary data about each file, and it could get really messy if we have lots of files produced for some reason.

Both ideas above don't handle the case where the underlying data is held in a number of files, because the code decided to split them up for parallel processing for example.
The user only needs to believe they have one logical file, not all the details underneath.

Anyway, after that rather lengthy introduction, how should I deal with this?

I though of returning some sort of Foo::IO object that contains all of the filenames that had been processed by a method, and all the information we might need. If the user wants to process the output from an early stage of the code, he just uses the old Foo::IO object.

General example:

my $munger=Munger->new( input => "data" );

# assume the original "data"
# since there's no Foo::IO argument
my $sort_result = $munger->sort(by => "date"); 

# Again, just use the input filename stored in 
# the main object - "data"
my $mangle_result = $munger->mangle(); 

# Use sorted file, and know that it's sorted by date
# Give it the sort result Foo::IO state object
my $subset_result = $munger->subset( by => date,
                                     $sort_result
                                    ); 
# etc.
[download]

When I mentioned my problem in the CB, jwest suggested using a object that contained several file objects that could be used for this sort of problem.

So, my questions are:

• Should I return some sort of Foo::IO/Foo::File object to encapsulate the files?
• How should I handle the IO object in relation to the main class (Foo) and the IO/File class?
• Is there some other way of handling state without real pain?
• Am I approaching this is the right way?

jwest's idea seems to make a lot of sense, but I've not yet been able to think out how the main class that does all the munging would use these state objects, and how it would all fit together.

Hopefully I've explained my problem with sufficient detail.
Thanks in advance.

BazB

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