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internal package Foswiki::ListIterator

See PublishedAPI for packages intended to be used by Plugin and Contrib authors, or browse all packages.
See also Developing plugins, Developer's Bible, Technical Overview

internal package Foswiki::ListIterator is a Foswiki::Iterator

implements Foswiki::Iterator

Iterator over a perl list

WARNING: this Iterator will skip any elements that are == undef. SMELL: hasNext should not 'return 1 if defined($this->{next}), but rather use a boolean - to allow array elements to be undef too.

new(\@list)

Create a new iterator over the given list. Designed primarily for operations over fully defined lists of object references. The list is not damaged in any way.

hasNext() -> $boolean

Returns false when the iterator is exhausted.

my $it = new Foswiki::ListIterator(\@list);
while ($it->hasNext()) {
   ...

skip(count) -> $countremaining

skip X elements (returns 0 if successful, or number of elements remaining to skip if there are not enough elements to skip) skip must set up next as though hasNext was called.

next() -> $data

Return the next entry in the list.

The iterator object can be customised to pre- and post-process entries from the list before returning them. This is done by setting two fields in the iterator object:

  • {filter} can be defined to be a sub that filters each entry. The entry will be ignored (next() will not return it) if the filter returns false.
  • {process} can be defined to be a sub to process each entry before it is returned by next. The value returned from next is the value returned by the process function.

For example,
my @list = ( 1, 2, 3 );

my $it = new Foswiki::ListIterator(\@list);
$it->{filter} = sub { return $_[0] != 2 };
$it->{process} = sub { return $_[0] + 1 };
while ($it->hasNext()) {
    my $x = $it->next();
    print "$x, ";
}
will print
2, 4

ObjectMethod all() → @list

Exhaust the iterator. Return all remaining elements in the iteration as a list. The returned list should be considered to be immutable.

This method is cheap if it is called when the cursor is at the first element in the iteration, and expensive otherwise, as it requires a list copy to be made.

reset() -> $boolean

Start at the begining of the list
$it->reset();
while ($it->hasNext()) {
   ...

r1 - 19 Apr 2011 - 03:38:03 - ProjectContributor
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