File Coverage

blib/lib/Iterator/Paged.pm

Criterion	Covered	Total	%
statement	20	25	80.0
branch	4	4	100.0
condition			n/a
subroutine	6	8	75.0
pod	4	5	80.0
total	34	42	80.9

package Iterator::Paged;

use strict;
use warnings 'all';

our $VERSION = '1.001';


#==============================================================================
sub new
{
  my ($class, %args) = @_;

  my $s = bless {
    data        => [ ],
    page_number => 0,
    idx         => 0,
    %args,
  }, $class;
  $s->_init;
  return $s;
}# end new()

sub _init { }


#==============================================================================
# Default just returns another random set of 10 digits:
sub next_page { shift->{page_number}++; [ map { rand() } 1..10 ] }


#==============================================================================
sub next
{
  my $s = shift;

  if( exists( $s->{data}->[ $s->{idx} ] ) )
  {
    return $s->{data}->[ $s->{idx}++ ];
  }
  else
  {
    # End of the current resultset, see if we can get another page of records:
    if( my $page = $s->next_page )
    {
      $s->{data} = $page;
      $s->{idx} = 0;
      return $s->{data}->[ $s->{idx}++ ];
    }
    else
    {
      # No more pages, no more data:
      return;
    }# end if()
  }# end if()
}# end next()


#==============================================================================
sub reset
{
  my $s = shift;

  $s->{idx} = 0;
}# end next()


#==============================================================================
sub page_number { shift->{page_number} }


1;# return true:

=pod

=head1 NAME

Iterator::Paged - Simple iterator with events for accessing more records.

=head1 SYNOPSIS

  use Iterator::Paged;

  my $iter = Iterator::Paged->new();
  while( my $item = $iter->next )
  {
    warn $iter->page_number . ": $item\n";
    last if $iter->page_number > 100;
  }# end while()

Or, more likely, in a subclass:

  package My::Iterator;

  use strict;
  use warnings 'all';
  use base 'Iterator::Paged';

  sub next_page
  {
    my ($s) = @_;

    # Return an arrayref of the next "page" of data:
    return if $s->{page_number}++ >= 4;
    return [ $s->{idx}.. $s->{idx} + 5  ];
  }# end get_page()

Then, using that class:

  use My::Iterator;

  my $iter = My::Iterator->new();

  while( my $item = $iter->next )
  {
    warn "Page " . $iter->page_number . ": $item\n";
  }# end while()

That last example will print the following:

  Page 1: 0
  Page 1: 1
  Page 1: 2
  Page 1: 3
  Page 1: 4
  Page 1: 5
  Page 2: 6
  Page 2: 7
  Page 2: 8
  Page 2: 9
  Page 2: 10
  Page 2: 11
  Page 3: 12
  Page 3: 13
  Page 3: 14
  Page 3: 15
  Page 3: 16
  Page 3: 17
  Page 4: 18
  Page 4: 19
  Page 4: 20
  Page 4: 21
  Page 4: 22
  Page 4: 23

=head1 DESCRIPTION

Iterator::Paged provides a simple (subclassable) iterator that will attempt to
fetch the next "page" of results when the current set is exhausted.

For example, suppose you have an iterator for results on Google.com that fetches
the first page of results and upon the next call to C fetches the second page,
then third page, fourth and so on.

=head1 PUBLIC PROPERTIES

=head2 next

Returns the next record.

=head2 page_number

Gets the current page number the iterator is on.

=head1 PUBLIC METHODS

=head2 reset

Sets the page number and internal index to C<0>.

=head1 ABSTRACT METHODS

The following methods should be implemented by subclasses of Iterator::Paged.

=head2 next_page( )

This method should somehow fetch the next "page" of records and upon success,
return an arrayref of records.

If no more records are available, the method should return C like so:

  # No records found:
  return;

=head1 PROTECTED METHODS

The following methods I be implemented by subclasses of Iterator::Paged.

=head2 _init( )

If your iterator class should be initialized after C and before C,
use C<_init> for that purpose.

=head1 AUTHOR

John Drago

=head1 COPYRIGHT

Copyright 2009 John Drago  all rights reserved.

=head1 LICENSE

This software is free software and may be used and redistributed under the same
terms as Perl itself.

=cut