oracular (3) Tree::Simple::Visitor.3pm.gz

NAME

       Tree::Simple::Visitor - Visitor object for Tree::Simple objects

SYNOPSIS

         use Tree::Simple;
         use Tree::Simple::Visitor;

         # create a visitor instance
         my $visitor = Tree::Simple::Visitor->new();

         # create a tree to visit
         my $tree = Tree::Simple->new(Tree::Simple->ROOT)
                                ->addChildren(
                                    Tree::Simple->new("1.0"),
                                    Tree::Simple->new("2.0")
                                                ->addChild(
                                                    Tree::Simple->new("2.1.0")
                                                    ),
                                    Tree::Simple->new("3.0")
                                    );

         # by default this will collect all the
         # node values in depth-first order into
         # our results
         $tree->accept($visitor);

         # get our results and print them
         print join ", ", $visitor->getResults();  # prints "1.0, 2.0, 2.1.0, 3.0"

         # for more complex node objects, you can specify
         # a node filter which will be used to extract the
         # information desired from each node
         $visitor->setNodeFilter(sub {
                       my ($t) = @_;
                       return $t->getNodeValue()->description();
                       });

         # NOTE: this object has changed, but it still remains
         # backwards compatible to the older version, see the
         # DESCRIPTION section below for more details

DESCRIPTION

       This object has been revised into what I think is more intelligent approach to Visitor objects.  This is
       now a more suitable base class for building your own Visitors. It is also the base class for the visitors
       found in the Tree::Simple::VisitorFactory distribution, which includes a number of useful pre-built
       Visitors.

       While I have changed a number of things about this module, I have kept it backwards compatible to the old
       way of using it. So the original example code still works:

         my @accumulator;
         my $visitor = Tree::Simple::Visitor->new(sub {
                               my ($tree) = @_;
                               push @accumulator, $tree->getNodeValue();
                               },
                               Tree::Simple::Visitor->RECURSIVE);

         $tree->accept($visitor);

         print join ", ", @accumulator;  # prints "1.0, 2.0, 2.1.0, 3.0"

       But is better expressed as this:

         my $visitor = Tree::Simple::Visitor->new();
         $tree->accept($visitor);
         print join ", ", $visitor->getResults();  # prints "1.0, 2.0, 2.1.0, 3.0"

       This object is still pretty much a wrapper around the Tree::Simple "traverse" method, and can be thought
       of as a depth-first traversal Visitor object.

METHODS

       new ($func, $depth)
           The new style interface means that all arguments to the constructor are now optional.  As a means of
           defining the usage of the old and new, when no arguments are sent to the constructor, it is assumed
           that the new style interface is being used. In the new style, the $depth is always assumed to be
           equivalent to "RECURSIVE" and the $func argument can be set with "setNodeFilter" instead. This is the
           recommended way of doing things now.  If you have been using the old way, it is still there, and I
           will maintain backwards compatibility for a few more version before removing it entirely. If you are
           using this module (and I do not even know if anyone actually is) you have been warned. Please contact
           me if this will be a problem.

           The old style constructor documentation is retained her for reference:

           The first argument to the constructor is a code reference to a function which expects a Tree::Simple
           object as its only argument. The second argument is optional, it can be used to set the depth to
           which the function is applied. If no depth is set, the function is applied to the current
           Tree::Simple instance. If $depth is set to "CHILDREN_ONLY", then the function will be applied to the
           current Tree::Simple instance and all its immediate children. If $depth is set to "RECURSIVE", then
           the function will be applied to the current Tree::Simple instance and all its immediate children, and
           all of their children recursively on down the tree. If no $depth is passed to the constructor, then
           the function will only be applied to the current Tree::Simple object and none
            of its children.

       includeTrunk ($boolean)
           Based upon the value of $boolean, this will tell the visitor to collect the trunk of the tree as
           well. It is defaulted to false (0) in the new style interface, but is defaulted to true (1) in the
           old style interface.

       getNodeFilter
           This method returns the CODE reference set with "setNodeFilter" argument.

       clearNodeFilter
           This method clears node filter field.

       setNodeFilter ($filter_function)
           This method accepts a CODE reference as its $filter_function argument. This code reference is used to
           filter the tree nodes as they are collected. This can be used to customize output, or to gather
           specific information from a more complex tree node. The filter function should accept a single
           argument, which is the current Tree::Simple object.

       getResults
           This method returns the accumulated results of the application of the node filter to the tree.

       setResults
           This method should not really be used outside of this class, as it just would not make any sense to.
           It is included in this class and in this documentation to facilitate subclassing of this class for
           your own needs. If you desire to clear the results, then you can simply call "setResults" with no
           argument.

       visit ($tree)
           The "visit" method accepts a Tree::Simple and applies the function set in "new" or "setNodeFilter"
           appropriately. The results of this application can be retrieved with "getResults"

CONSTANTS

       These constants are part of the old-style interface, and therefore will eventually be deprecated.

       RECURSIVE
           If passed this constant in the constructor, the function will be applied recursively down the
           hierarchy of Tree::Simple objects.

       CHILDREN_ONLY
           If passed this constant in the constructor, the function will be applied to the immediate children of
           the Tree::Simple object.

BUGS

       None that I am aware of. The code is pretty thoroughly tested (see CODE COVERAGE section in Tree::Simple)
       and is based on an (non-publicly released) module which I had used in production systems for about 2
       years without incident. Of course, if you find a bug, let me know, and I will be sure to fix it.

       Bugs should be reported via the CPAN bug tracker at

       <https://github.com/ronsavage/Tree-Simple/issues>

SEE ALSO

       I have written a set of pre-built Visitor objects, available on CPAN as Tree::Simple::VisitorFactory.

AUTHOR

       stevan little, <stevan@iinteractive.com>

REPOSITORY

       <https://github.com/ronsavage/Tree-Simple>.

COPYRIGHT AND LICENSE

       Copyright 2004-2006 by Infinity Interactive, Inc.

       <http://www.iinteractive.com>

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