Philip Crow > Class-Colon > Class::Colon

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NAME ^

Class::Colon - Makes objects out of colon delimited records and vice versa

VERSION ^

This document covers version 0.03 of Class::Colon.

SYNOPSIS ^

    use Date;
    use Class::Colon
        Person  => [ qw ( first middle family date_of_birth=Date=new ) ],
        Address => [ qw ( street city province code country          ) ];

    Person->DELIM(','); # change from colon to comma for delimeter
    my $names = Person->READ_FILE($file_name);
    foreach my $name (@$names) {
        print $name->family, ",", $name->first, $name->middle, "\n";
    }

    open ADDRESS_FILE, "addresses.dat" or die "...\n";
    my $addresses = Address->READ_HANDLE(*ADDRESS_FILE);
    foreach my $address (@$addresses) {
        print $address->street . "\n"
        print $address->city . ", " . $address->province . "\n";
        print $address->country, "\n" if $address->country;
    }
    close ADDRESS_FILE;

    my $sample_address = Address->OBJECTIFY(
        "1313 Mocking Bird Ln:Adamstown:PA:12345:USA"
    );  # convert one string to an object

    my $first_address = $addresses->[0]->STRINGIFY();
    # puts it back in delimited form

    Address->WRITE_FILE("output.dat", $addresses);
    
    open ADDRESS_FILE, ">newaddr.dat" or die "...\n";
    Address->WRITE_HANDLE(*ADDRESS_FILE, $addresses);
    close ADDRESS_FILE;

DESCRIPTION ^

To turn your colon delimited file into a list of objects, use Class::Colon, giving it the name you want to use for the class and an anonymous array of column names which will become attributes of the objects in the class. List the names in the order they appear in the input. Missing fields will be set to "". Extra fields will be ignored. Use lower case names for the fields. Upper case names are reserved for use as methods of the class.

Most fields will be simple scalars, but if one of the fields should be an object, its entry should be of the form

    attribute_name=package_name=constructor_name

as shown above for date_of_birth which is of type Date whose constructor is new. In that example, I could have omitted the constructor name, since new is the default.

You may objectify as many different record types as you like in one use statement. You may have multiple use statements throughout your program or module. If you are using this package from another package, you should worry a little about namespace collision. There is only one list of classes made by this package. The names must be unique or Bad Things will happen. Feel free to include your module name in the names of the fabricated classes as in:

    package YourModule;
    use Class::Colon YourModule::Person => [ qw( field names here ) ];

You wouldn't have to use the double colon, but it makes sense to me.

If your delimiter is not colon, call DELIM on your class before calling READ_*. Pass it as a string. It can be any length, but is taken literally.

Feel free to add code to the generated package(s) before or after using Class::Colon. But, keep in mind possible name conflicts. As pointed out below (under METHODS), all ALL_CAPS names are reserved.

ABSTRACT ^

  This module turns colon separated data files into lists of objects.

EXPORT

None, this is object oriented.

METHODS ^

There are currently only a few methods. There are two class methods for reading, READ_FILE and READ_HANDLE, (these work for every class you requested in your use Class::Colon statement). There are corresponding class methods for writing, WRITE_FILE and WRITE_HANDLE. If you want to handle the I/O manually (or maybe you don't need I/O), there are two methods to help, OBJECTIFY (takes a string returns an object) and STRINGIFY (the opposite). There is also a set of dual use accessors, one for each field in each class. You name these yourself in the use statement. Finally, there is a DELIM method which allows you to set the delimiter. This can be any literal string, it applies to all fields in the file. There is a separate delimiter for each class. It defaults to colon.

You should consider every ALL_CAPS name reserved. I reserve the right to add methods in the future, their names will be ALL_CAPS, as the current method names are. Therefore, don't use ALL_CAPS for field names.

In addition to retrieving the attributes through accessor methods, you could peek directly at the data. It is stored in a hash so the following are equivalent:

    my $country = $address->country();

and

    my $country = $address->{country};

Using this fact might make some things neater in your code (like print statements). It also saves a tiny amount of time. Our OO teachers will smack our hands, if they hear about this little arrangement, so keep quite about it :-). I have no plans to change the implementation, but they tell me never to make such promises.

DELIM

Call this through one of the names you supplied in your use statement. Pass it a string. For example, you could say

    Person->DELIM(';');

this would change the delimiter from colon to semi-colon for Person. No other classes would be affected.

READ_FILE and READ_HANDLE

Call these mehtods through one of the names you supplied in your use statement.

Both READ_FILE and READ_HANDLE return an array reference with one element for each line in your input file. All lines are represented even if they are blank or start with #. The array elements are objects of the same type as the name you used to call the method. Think of these as super constructors, instead of making one object at a time, they make as many as they can from your input.

READ_FILE takes the name of a file, which it opens, reads, and closes.

READ_HANDLE takes an open handle ready for reading. You must ensure that the handle is properly opened and closed.

OBJECTIFY

If you want to control the read loop for your data, this method is here to help you. Call it through a class name. Pass it one line (chomp it yourself). Receive one object.

WRITE_FILE and WRITE_HANDLE

Call these mehtods through one of the names you supplied in your use statement.

Both WRITE_FILE and WRITE_HANDLE return an array reference with one element for each line in your input file. The lines are made by joining the fields in the order they appeared in the use statement using the current DELIM.

WRITE_FILE takes the name of a file, which it opens, writes, and closes.

WRITE_HANDLE takes a handle open for writing. You must ensure that the handle is properly opened and closed.

STRINGIFY

Call this through an object you got by using Class::Colon. Receive a colon delimited string suitable for writing back to your file. The string comes with no newline, unless the last field happens to have one. You may need to supply a newline, especially if you chomped.

accessors

For each attribute you name in your use statement, there is a corresponding dual use accessor. The names of the accessors are the same as the names you used (how convenient). You can also fish directly in the hash based object using the name of attribute as the key, but don't tell your OO instructor.

BUGS and OMISSIONS ^

There is no quoting. If a colon (or the DELIM of your choice) is quoted, it still counts as a field separator.

Comments and blank lines are treated as regular records.

AUTHOR ^

Phil Crow, <philcrow2000@yahoo.com>

COPYRIGHT AND LICENSE ^

Copyright 2003 by Phil Crow, all rights reserved.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl 5.8.1 itself.

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