NAME

       Data::TableReader::Field - Field specification for Data::TableReader

VERSION

       version 0.011

DESCRIPTION

       This class describes aspects of one of the fields you want to find in your spreadsheet.

ATTRIBUTES

   name
       Required.  Used for the hashref key if you pull records as hashes, and used in diagnostic
       messages.

   header
       A string or regex describing the column header you want to find in the spreadsheet.  If
       you specify a regex, it is used directly.  If you specify a string, it becomes the regex
       matching any string with the same words (\w+) and non-whitespace (\S+) characters in the
       same order, case insensitive, surrounded by any amount of non-alphanumeric garbage
       ("[\W_]*").  When no header is specified, the "name" is used as a string after first
       breaking it into words on underscore or camel-case or numeric boundaries.

       This deserves some examples:

         Name           Implied Default Header
         "zipcode"      "zipcode"
         "ZipCode"      "Zip Code"
         "Zip_Code"     "zip Code"
         "zip5"         "zip 5"

         Header         Regex                                  Could Match...
         "ZipCode"      /^[\W_]*ZipCode[\W_]*$/i               "zipcode:"
         "zip_code"     /^[\W_]*zip_code[\W_]*$/i              "--ZIP_CODE--"
         "zip code"     /^[\W_]*zip[\W_]*code[\W_]*$/i         "ZIP\nCODE    "
         "zip-code"     /^[\W_]*zip[\W_]*-[\W_]*code[\W_]*$/i  "ZIP-CODE:"
         qr/Zip.*Code/  /Zip.*Code/                            "Post(Zip)Code"

       If this default matching doesn't meet your needs or paranoia level, then you should always
       specify your own header regexes.

       (If your data actually doesn't have any header at all and you want to brazenly assume the
       columns match the fields, see reader attribute "header_row_at" in Data::TableReader)

   required
       Whether or not this field must be found in order to detect a table.  Defaults is true.
       Note this does not require the field of a row to contain data in order to read a record
       from the table; it just requires a column to exist.

   trim
         # remove leading/trailing whitespace
         trim => 1

         # remove leading/trailing whitespace but also remove "N/A" and "NULL"
         trim => qr( ^ \s* N/A \s* $ | ^ \s* NULL \s* $ | ^ \s+ | \s+ $ )xi

         # custom search/replace in a coderef
         trim => sub { s/[\0-\1F\7F]+/ /g; s/^\s+//; s/\s+$//; };

       If set to a non-reference, this is treated as a boolean of whether to remove leading and
       trailing whitespace.  If set to a coderef, the coderef will be called for each value with
       $_ set to the current value; it should modify $_ as appropriate (return value is ignored).
       It can also be set to a regular expression of all the patterns to remove, as per
       "s/$regexp//g".

       Default is 1, which is equivalent to a regular expression of "qr/(^\s+)|(\s+$)/".

   blank
       The value to extract when the spreadsheet cell is an empty string or undef.  (after any
       processing done by "trim")  Default is "undef".  Another common value would be "".

   type
       A Type::Tiny type (or any object or class with a "validate" method) or a coderef which
       returns a validation error message (undef if it is valid).

         use Types::Standard;
         ...
            type => Maybe[Int]

         # or without Type::Tiny
            type => sub { $_[0] =~ /^\w+/? undef : "word-characters only" },

       This is an optional feature and there is no default.  The behavior of a validation failure
       depends on the options to TableReader.

   array
       Boolean of whether this field can be found multiple times in one table.  Default is false.
       If true, the value of the field will always be an arrayref (even if only one column
       matched).

   follows
       Name (or arrayref of names) of a field which this field must follow, in a first-to-last
       ordering of the columns.  This field must occur immediately after the named field(s), or
       after another field which also has a "follows" restriction and follows the named field(s).

       The purpose of this attribute is to resolve ambiguous columns.  Suppose you expect columns
       with the following headers:

         Father    |          |      |       | Mother    |          |      |
         FirstName | LastName | Tel. | Email | FirstName | LastName | Tel. | Email

       You can use "qr/Father\nFirstName/" to identify the first column, but after FirstName the
       rest are ambiguous.  But, TableReader can figure it out if you say:

         { name => 'father_first', header => qr/Father\nFirstName/ },
         { name => 'father_last',  header => 'LastName', follows => 'father_first' },
         { name => 'father_tel',   header => 'Tel.',     follows => 'father_first' },
         { name => 'father_email', header => 'Email',    follows => 'father_first' },
         ..

       and so on.  Note how 'father_first' is used for each as the "follows" name; this way if
       any non-required fields (like maybe "Tel") are completely removed from the file,
       TableReader will still be able to find "LastName" and "Email".

       You can also use this to accumulate an array of columns that lack headers:

         Scores |      |       |      |       |       |       | OtherData
         12%    | 35%  | 42%   | 18%  | 65%   | 99%   | 55%   | xyz

         { name => 'scores', array => 1, trim => 1 },
         { name => 'scores', array => 1, trim => 1, header => '', follows => 'scores' },

       The second field definition has an empty header, which would normally make it rather
       ambiguous and potentially capture blank-header columns that might not be part of the
       array.  But, because it must follow a column named 'scores' there's no ambiguity; you get
       exactly any column starting from the header 'Scores' until a column of any other header.

   follows_list
       Convenience accessor for "@{ ->follows }", useful because "follows" might only be a
       scalar.

   header_regex
       "header", coerced to a regex if it wasn't already

AUTHOR

       Michael Conrad <mike@nrdvana.net>

COPYRIGHT AND LICENSE

       This software is copyright (c) 2019 by Michael Conrad.

       This is free software; you can redistribute it and/or modify it under the same terms as
       the Perl 5 programming language system itself.