1Tree::Simple::Visitor(3U)ser Contributed Perl DocumentatiTornee::Simple::Visitor(3)
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NAME

6       Tree::Simple::Visitor - Visitor object for Tree::Simple objects
7

SYNOPSIS

9         use Tree::Simple;
10         use Tree::Simple::Visitor;
11
12         # create a visitor instance
13         my $visitor = Tree::Simple::Visitor->new();
14
15         # create a tree to visit
16         my $tree = Tree::Simple->new(Tree::Simple->ROOT)
17                                ->addChildren(
18                                    Tree::Simple->new("1.0"),
19                                    Tree::Simple->new("2.0")
20                                                ->addChild(
21                                                    Tree::Simple->new("2.1.0")
22                                                    ),
23                                    Tree::Simple->new("3.0")
24                                    );
25
26         # by default this will collect all the
27         # node values in depth-first order into
28         # our results
29         $tree->accept($visitor);
30
31         # get our results and print them
32         print join ", ", $visitor->getResults();  # prints "1.0, 2.0, 2.1.0, 3.0"
33
34         # for more complex node objects, you can specify
35         # a node filter which will be used to extract the
36         # information desired from each node
37         $visitor->setNodeFilter(sub {
38                       my ($t) = @_;
39                       return $t->getNodeValue()->description();
40                       });
41
42         # NOTE: this object has changed, but it still remains
43         # backwards compatible to the older version, see the
44         # DESCRIPTION section below for more details
45

DESCRIPTION

47       This object has been revised into what I think is more intelligent
48       approach to Visitor objects. This is now a more suitable base class for
49       building your own Visitors. It is also the base class for the visitors
50       found in the Tree::Simple::VisitorFactory distribution, which includes
51       a number of useful pre-built Visitors.
52
53       While I have changed a number of things about this module, I have kept
54       it backwards compatible to the old way of using it. So the original
55       example code still works:
56
57         my @accumulator;
58         my $visitor = Tree::Simple::Visitor->new(sub {
59                               my ($tree) = @_;
60                               push @accumlator, $tree->getNodeValue();
61                               },
62                               Tree::Simple::Visitor->RECURSIVE);
63
64         $tree->accept($visitor);
65
66         print join ", ", @accumulator;  # prints "1.0, 2.0, 2.1.0, 3.0"
67
68       But is better expressed as this:
69
70         my $visitor = Tree::Simple::Visitor->new();
71         $tree->accept($visitor);
72         print join ", ", $visitor->getResults();  # prints "1.0, 2.0, 2.1.0, 3.0"
73
74       This object is still pretty much a wrapper around the Tree::Simple
75       "traverse" method, and can be thought of as a depth-first traversal
76       Visitor object.
77

METHODS

79       new ($func, $depth)
80           The new style interface means that all arguments to the constructor
81           are now optional. As a means of defining the usage of the old and
82           new, when no arguments are sent to the constructor, it is assumed
83           that the new style interface is being used. In the new style, the
84           $depth is always assumed to be equivalent to "RECURSIVE" and the
85           $func argument can be set with "setNodeFilter" instead. This is the
86           recommended way of doing things now. If you have been using the old
87           way, it is still there, and I will maintain backwards compatability
88           for a few more version before removing it entirely. If you are
89           using this module (and I don't even know if anyone actually is) you
90           have been warned. Please contact me if this will be a problem.
91
92           The old style constructor documentation is retained her for
93           reference:
94
95           The first argument to the constructor is a code reference to a
96           function which expects a Tree::Simple object as its only argument.
97           The second argument is optional, it can be used to set the depth to
98           which the function is applied. If no depth is set, the function is
99           applied to the current Tree::Simple instance. If $depth is set to
100           "CHILDREN_ONLY", then the function will be applied to the current
101           Tree::Simple instance and all its immediate children. If $depth is
102           set to "RECURSIVE", then the function will be applied to the
103           current Tree::Simple instance and all its immediate children, and
104           all of their children recursively on down the tree. If no $depth is
105           passed to the constructor, then the function will only be applied
106           to the current Tree::Simple object and none of its children.
107
108       includeTrunk ($boolean)
109           Based upon the value of $boolean, this will tell the visitor to
110           collect the trunk of the tree as well. It is defaulted to false (0)
111           in the new style interface, but is defaulted to true (1) in the old
112           style interface.
113
114       getNodeFilter
115           This method returns the CODE reference set with "setNodeFilter"
116           argument.
117
118       clearNodeFilter
119           This method clears node filter field.
120
121       setNodeFilter ($filter_function)
122           This method accepts a CODE reference as its $filter_function
123           argument. This code reference is used to filter the tree nodes as
124           they are collected. This can be used to customize output, or to
125           gather specific information from a more complex tree node. The
126           filter function should accept a single argument, which is the
127           current Tree::Simple object.
128
129       getResults
130           This method returns the accumulated results of the application of
131           the node filter to the tree.
132
133       setResults
134           This method should not really be used outside of this class, as it
135           just would not make any sense to. It is included in this class and
136           in this documenation to facilitate subclassing of this class for
137           your own needs. If you desire to clear the results, then you can
138           simply call "setResults" with no argument.
139
140       visit ($tree)
141           The "visit" method accepts a Tree::Simple and applies the function
142           set in "new" or "setNodeFilter" appropriately. The results of this
143           application can be retrieved with "getResults"
144

CONSTANTS

146       These constants are part of the old-style interface, and therefore will
147       eventually be deprecated.
148
149       RECURSIVE
150           If passed this constant in the constructor, the function will be
151           applied recursively down the hierarchy of Tree::Simple objects.
152
153       CHILDREN_ONLY
154           If passed this constant in the constructor, the function will be
155           applied to the immediate children of the Tree::Simple object.
156

BUGS

158       None that I am aware of. The code is pretty thoroughly tested (see CODE
159       COVERAGE section in Tree::Simple) and is based on an (non-publicly
160       released) module which I had used in production systems for about 2
161       years without incident. Of course, if you find a bug, let me know, and
162       I will be sure to fix it.
163

SEE ALSO

165       I have written a set of pre-built Visitor objects, available on CPAN as
166       Tree::Simple::VisitorFactory.
167

AUTHOR

169       stevan little, <stevan@iinteractive.com>
170
172       Copyright 2004-2006 by Infinity Interactive, Inc.
173
174       <http://www.iinteractive.com>
175
176       This library is free software; you can redistribute it and/or modify it
177       under the same terms as Perl itself.
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181perl v5.12.0                      2007-11-11          Tree::Simple::Visitor(3)
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