Template::Iterator(3)

NAME
Template::Iterator - Data iterator used by the FOREACH directive

SYNOPSIS
    my $iter = Template::Iterator->new(\@data, \%options);

DESCRIPTION
The "Template::Iterator" module defines a generic data iterator for use by the "FOREACH" directive.

It may be used as the base class for custom iterators.

PUBLIC METHODS

  new($data)
Constructor method. A reference to a list of values is passed as the first parameter. Subsequent calls to get_first() and get_next() calls will return each element from the list.

    my $iter = Template::Iterator->new([ 'foo', 'bar', 'baz' ]);

The constructor will also accept a reference to a hash array and will expand it into a list in which each entry is a hash array containing a '"key"' and '"value"' item, sorted according to the hash keys.

    my $iter = Template::Iterator->new({
        foo => 'Foo Item',
        bar => 'Bar Item',
    });

This is equivalent to:

    my $iter = Template::Iterator->new([
        { key => 'bar', value => 'Bar Item' },
        { key => 'foo', value => 'Foo Item' },
    ]);

When passed a single item which is not an array reference, the constructor will automatically create a list containing that single item.

    my $iter = Template::Iterator->new('foo');

This is equivalent to:

    my $iter = Template::Iterator->new([ 'foo' ]);

Note that a single item which is an object based on a blessed ARRAY references will NOT be treated as an array and will be folded into a list containing that one object reference.

    my $list = bless [ 'foo', 'bar' ], 'MyListClass';
    my $iter = Template::Iterator->new($list);

equivalent to:

    my $iter = Template::Iterator->new([ $list ]);

If the object provides an as_list() method then the Template::Iterator constructor will call that method to return the list of data. For example:

    package MyListObject;

    sub new {
        my $class = shift;
        bless [ @_ ], $class;
    }

    package main;

    my $list = MyListObject->new('foo', 'bar');
    my $iter = Template::Iterator->new($list);

This is then functionally equivalent to:

    my $iter = Template::Iterator->new([ $list ]);

The iterator will return only one item, a reference to the "MyListObject" object, $list.

By adding an as_list() method to the "MyListObject" class, we can force the "Template::Iterator" constructor to treat the object as a list and use the data contained within.

    package MyListObject;

    ...

    sub as_list {
        my $self = shift;
        return $self;
    }

    package main;

    my $list = MyListObject->new('foo', 'bar');
    my $iter = Template::Iterator->new($list);

The iterator will now return the two items, '"foo"' and '"bar"', which the "MyObjectList" encapsulates.

  get_first()
Returns a "($value, $error)" pair for the first item in the iterator set. The $error returned may be zero or undefined to indicate a valid datum was successfully returned. Returns an error of "STATUS_DONE" if the list is empty.

  get_next()
Returns a "($value, $error)" pair for the next item in the iterator set. Returns an error of "STATUS_DONE" if all items in the list have been visited.

  get_all()
Returns a "(\@values, $error)" pair for all remaining items in the iterator set. Returns an error of "STATUS_DONE" if all items in the list have been visited.

  size()
Returns the size of the data set or undef if unknown.

  max()
Returns the maximum index number (i.e. the index of the last element) which is equivalent to size() - 1.

  index()
Returns the current index number which is in the range 0 to max().

  count()
Returns the current iteration count in the range 1 to size(). This is equivalent to index() + 1.

  first()
Returns a boolean value to indicate if the iterator is currently on the first iteration of the set.

  last()
Returns a boolean value to indicate if the iterator is currently on the last iteration of the set.

  prev()
Returns the previous item in the data set, or "undef" if the iterator is on the first item.

  next()
Returns the next item in the data set or "undef" if the iterator is on the last item.

  number()
This is an alias to 'count' to provide backward compatibility. View count.

  parity()
Returns the text string "even" or "odd" to indicate the parity of the current iteration count (starting at 1). This is typically used to create striped zebra tables.

    <table>
    [% FOREACH name IN ['Arthur', 'Ford', 'Trillian'] -%]
      <tr class="[% loop.parity %]">
        <td>[% name %]</td>
      </tr>
    [% END %]
    </table>

This will produce the following output:

    <table>
      <tr class="odd">
        <td>Arthur</td>
      </tr>
      <tr class="even">
        <td>Ford</td>
      </tr>
      <tr class="odd">
        <td>Trillian</td>
      </tr>
    </table>

You can then style the "tr.odd" and "tr.even" elements using CSS:

    tr.odd td {
        background-color: black;
        color: white;
    }

    tr.even td {
        background-color: white;
        color: black;
    }

  odd()
Returns a boolean (0/1) value to indicate if the current iterator count (starting at 1) is an odd number. In other words, this will return a true value for the first iterator, the third, fifth, and so on.

  even()
Returns a boolean (0/1) value to indicate if the current iterator count (starting at 1) is an even number. In other words, this will return a true value for the second iteration, the fourth, sixth, and so on.

AUTHOR
Andy Wardley <abw@wardley.org> <http://wardley.org/>

COPYRIGHT
Copyright (C) 1996-2022 Andy Wardley. All Rights Reserved.

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

SEE ALSO
Template