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#============================================================= -*-Perl-*-
#
# Template::Iterator
#
# DESCRIPTION
#
# Module defining an iterator class which is used by the FOREACH
# directive for iterating through data sets. This may be
# sub-classed to define more specific iterator types.
#
# AUTHOR
# Andy Wardley <abw@wardley.org>
#
# COPYRIGHT
# Copyright (C) 1996-2007 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.
#
#============================================================================
package Template::Iterator;
use strict;
use warnings;
use base 'Template::Base';
use Template::Constants;
use Template::Exception;
use Scalar::Util qw(blessed);
use constant ODD => 'odd';
use constant EVEN => 'even';
our $VERSION = 2.68;
our $DEBUG = 0 unless defined $DEBUG;
our $AUTOLOAD;
#========================================================================
# ----- CLASS METHODS -----
#========================================================================
#------------------------------------------------------------------------
# new(\@target, \%options)
#
# Constructor method which creates and returns a reference to a new
# Template::Iterator object. A reference to the target data (array
# or hash) may be passed for the object to iterate through.
#------------------------------------------------------------------------
sub new {
my $class = shift;
my $data = shift || [ ];
my $params = shift || { };
if (ref $data eq 'HASH') {
# map a hash into a list of { key => ???, value => ??? } hashes,
# one for each key, sorted by keys
$data = [ map { { key => $_, value => $data->{ $_ } } }
sort keys %$data ];
}
elsif (blessed($data) && $data->can('as_list')) {
$data = $data->as_list();
}
elsif (ref $data ne 'ARRAY') {
# coerce any non-list data into an array reference
$data = [ $data ] ;
}
bless {
_DATA => $data,
_ERROR => '',
}, $class;
}
#========================================================================
# ----- PUBLIC OBJECT METHODS -----
#========================================================================
#------------------------------------------------------------------------
# get_first()
#
# Initialises the object for iterating through the target data set. The
# first record is returned, if defined, along with the STATUS_OK value.
# If there is no target data, or the data is an empty set, then undef
# is returned with the STATUS_DONE value.
#------------------------------------------------------------------------
sub get_first {
my $self = shift;
my $data = $self->{ _DATA };
$self->{ _DATASET } = $self->{ _DATA };
my $size = scalar @$data;
my $index = 0;
return (undef, Template::Constants::STATUS_DONE) unless $size;
# initialise various counters, flags, etc.
@$self{ qw( SIZE MAX INDEX COUNT FIRST LAST ) }
= ( $size, $size - 1, $index, 1, 1, $size > 1 ? 0 : 1, undef );
@$self{ qw( PREV NEXT ) } = ( undef, $self->{ _DATASET }->[ $index + 1 ]);
return $self->{ _DATASET }->[ $index ];
}
#------------------------------------------------------------------------
# get_next()
#
# Called repeatedly to access successive elements in the data set.
# Should only be called after calling get_first() or a warning will
# be raised and (undef, STATUS_DONE) returned.
#------------------------------------------------------------------------
sub get_next {
my $self = shift;
my ($max, $index) = @$self{ qw( MAX INDEX ) };
my $data = $self->{ _DATASET };
# warn about incorrect usage
unless (defined $index) {
my ($pack, $file, $line) = caller();
warn("iterator get_next() called before get_first() at $file line $line\n");
return (undef, Template::Constants::STATUS_DONE); ## RETURN ##
}
# if there's still some data to go...
if ($index < $max) {
# update counters and flags
$index++;
@$self{ qw( INDEX COUNT FIRST LAST ) }
= ( $index, $index + 1, 0, $index == $max ? 1 : 0 );
@$self{ qw( PREV NEXT ) } = @$data[ $index - 1, $index + 1 ];
return $data->[ $index ]; ## RETURN ##
}
else {
return (undef, Template::Constants::STATUS_DONE); ## RETURN ##
}
}
#------------------------------------------------------------------------
# get_all()
#
# Method which returns all remaining items in the iterator as a Perl list
# reference. May be called at any time in the life-cycle of the iterator.
# The get_first() method will be called automatically if necessary, and
# then subsequent get_next() calls are made, storing each returned
# result until the list is exhausted.
#------------------------------------------------------------------------
sub get_all {
my $self = shift;
my ($max, $index) = @$self{ qw( MAX INDEX ) };
my @data;
# handle cases where get_first() has yet to be called.
unless (defined $index) {
my ($first, $status) = $self->get_first;
# refresh $max and $index, after get_first updates MAX and INDEX
($max, $index) = @$self{ qw( MAX INDEX ) };
# empty lists are handled here.
if ($status && $status == Template::Constants::STATUS_DONE) {
return (undef, Template::Constants::STATUS_DONE); ## RETURN ##
}
push @data, $first;
## if there's nothing left in the iterator, return the single value.
unless ($index < $max) {
return \@data;
}
}
# if there's still some data to go...
if ($index < $max) {
$index++;
push @data, @{ $self->{ _DATASET } } [ $index..$max ];
# update counters and flags
@$self{ qw( INDEX COUNT FIRST LAST ) }
= ( $max, $max + 1, 0, 1 );
return \@data; ## RETURN ##
}
else {
return (undef, Template::Constants::STATUS_DONE); ## RETURN ##
}
}
sub odd {
shift->{ COUNT } % 2 ? 1 : 0
}
sub even {
shift->{ COUNT } % 2 ? 0 : 1
}
sub parity {
shift->{ COUNT } % 2 ? ODD : EVEN;
}
#------------------------------------------------------------------------
# AUTOLOAD
#
# Provides access to internal fields (e.g. size, first, last, max, etc)
#------------------------------------------------------------------------
sub AUTOLOAD {
my $self = shift;
my $item = $AUTOLOAD;
$item =~ s/.*:://;
return if $item eq 'DESTROY';
# alias NUMBER to COUNT for backwards compatibility
$item = 'COUNT' if $item =~ /NUMBER/i;
return $self->{ uc $item };
}
#========================================================================
# ----- PRIVATE DEBUG METHODS -----
#========================================================================
#------------------------------------------------------------------------
# _dump()
#
# Debug method which returns a string detailing the internal state of
# the iterator object.
#------------------------------------------------------------------------
sub _dump {
my $self = shift;
join('',
" Data: ", $self->{ _DATA }, "\n",
" Index: ", $self->{ INDEX }, "\n",
"Number: ", $self->{ NUMBER }, "\n",
" Max: ", $self->{ MAX }, "\n",
" Size: ", $self->{ SIZE }, "\n",
" First: ", $self->{ FIRST }, "\n",
" Last: ", $self->{ LAST }, "\n",
"\n"
);
}
1;
__END__
=head1 NAME
Template::Iterator - Data iterator used by the FOREACH directive
=head1 SYNOPSIS
my $iter = Template::Iterator->new(\@data, \%options);
=head1 DESCRIPTION
The C<Template::Iterator> module defines a generic data iterator for use
by the C<FOREACH> directive.
It may be used as the base class for custom iterators.
=head1 PUBLIC METHODS
=head2 new($data)
Constructor method. A reference to a list of values is passed as the
first parameter. Subsequent calls to L<get_first()> and L<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 'C<key>' and 'C<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 C<as_list()> method then the L<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([ $list ]);
The iterator will return only one item, a reference to the C<MyListObject>
object, C<$list>.
By adding an C<as_list()> method to the C<MyListObject> class, we can force
the C<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, 'C<foo>' and 'C<bar>', which the
C<MyObjectList> encapsulates.
=head2 get_first()
Returns a C<($value, $error)> pair for the first item in the iterator set.
The C<$error> returned may be zero or undefined to indicate a valid datum
was successfully returned. Returns an error of C<STATUS_DONE> if the list
is empty.
=head2 get_next()
Returns a C<($value, $error)> pair for the next item in the iterator set.
Returns an error of C<STATUS_DONE> if all items in the list have been
visited.
=head2 get_all()
Returns a C<(\@values, $error)> pair for all remaining items in the iterator
set. Returns an error of C<STATUS_DONE> if all items in the list have been
visited.
=head2 size()
Returns the size of the data set or undef if unknown.
=head2 max()
Returns the maximum index number (i.e. the index of the last element)
which is equivalent to L<size()> - C<1>.
=head2 index()
Returns the current index number which is in the range C<0> to L<max()>.
=head2 count()
Returns the current iteration count in the range C<1> to L<size()>. This is
equivalent to L<index()> + C<1>.
=head2 first()
Returns a boolean value to indicate if the iterator is currently on
the first iteration of the set.
=head2 last()
Returns a boolean value to indicate if the iterator is currently on
the last iteration of the set.
=head2 prev()
Returns the previous item in the data set, or C<undef> if the iterator is
on the first item.
=head2 next()
Returns the next item in the data set or C<undef> if the iterator is on the
last item.
=head2 parity()
Returns the text string C<even> or C<odd> to indicate the parity of the
current iteration count (starting at 1). This is typically used to create
striped I<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 C<tr.odd> and C<tr.even> elements using CSS:
tr.odd td {
background-color: black;
color: white;
}
tr.even td {
background-color: white;
color: black;
}
=head2 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.
=head2 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.
=head1 AUTHOR
Andy Wardley E<lt>abw@wardley.orgE<gt> L<http://wardley.org/>
=head1 COPYRIGHT
Copyright (C) 1996-2007 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.
=head1 SEE ALSO
L<Template>
=cut
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