1Tree::Simple::Visitor(3U)ser Contributed Perl DocumentatiTornee::Simple::Visitor(3)
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6 Tree::Simple::Visitor - Visitor object for Tree::Simple objects
7
9 use Tree::Simple;
10 use Tree::Simple::Visitor;
11 # create a visitor instance
13 my $visitor = Tree::Simple::Visitor->new();
14 # 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 # by default this will collect all the
27 # node values in depth-first order into
28 # our results
29 $tree->accept($visitor);
30 # get our results and print them
32 print join ", ", $visitor->getResults(); # prints "1.0, 2.0, 2.1.0, 3.0"
33 # 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 # 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
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
49 for building your own Visitors. It is also the base class for the
50 visitors found in the Tree::Simple::VisitorFactory distribution, which
51 includes a number of useful pre-built Visitors.
52 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 my @accumulator;
58 my $visitor = Tree::Simple::Visitor->new(sub {
59 my ($tree) = @_;
60 push @accumulator, $tree->getNodeValue();
61 },
62 Tree::Simple::Visitor->RECURSIVE);
63 $tree->accept($visitor);
65 print join ", ", @accumulator; # prints "1.0, 2.0, 2.1.0, 3.0"
67 But is better expressed as this:
69 my $visitor = Tree::Simple::Visitor->new();
71 $tree->accept($visitor);
72 print join ", ", $visitor->getResults(); # prints "1.0, 2.0, 2.1.0, 3.0"
73 This object is still pretty much a wrapper around the Tree::Simple
75 "traverse" method, and can be thought of as a depth-first traversal
76 Visitor object.
77
79 new ($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
87 old way, it is still there, and I will maintain backwards
88 compatibility for a few more version before removing it entirely.
89 If you are using this module (and I do not even know if anyone
90 actually is) you have been warned. Please contact me if this will
91 be a problem.
92 The old style constructor documentation is retained her for
94 reference:
95 The first argument to the constructor is a code reference to a
97 function which expects a Tree::Simple object as its only argument.
98 The second argument is optional, it can be used to set the depth to
99 which the function is applied. If no depth is set, the function is
100 applied to the current Tree::Simple instance. If $depth is set to
101 "CHILDREN_ONLY", then the function will be applied to the current
102 Tree::Simple instance and all its immediate children. If $depth is
103 set to "RECURSIVE", then the function will be applied to the
104 current Tree::Simple instance and all its immediate children, and
105 all of their children recursively on down the tree. If no $depth is
106 passed to the constructor, then the function will only be applied
107 to the current Tree::Simple object and none
108 of its children.
109 includeTrunk ($boolean)
111 Based upon the value of $boolean, this will tell the visitor to
112 collect the trunk of the tree as well. It is defaulted to false (0)
113 in the new style interface, but is defaulted to true (1) in the old
114 style interface.
115 getNodeFilter
117 This method returns the CODE reference set with "setNodeFilter"
118 argument.
119 clearNodeFilter
121 This method clears node filter field.
122 setNodeFilter ($filter_function)
124 This method accepts a CODE reference as its $filter_function
125 argument. This code reference is used to filter the tree nodes as
126 they are collected. This can be used to customize output, or to
127 gather specific information from a more complex tree node. The
128 filter function should accept a single argument, which is the
129 current Tree::Simple object.
130 getResults
132 This method returns the accumulated results of the application of
133 the node filter to the tree.
134 setResults
136 This method should not really be used outside of this class, as it
137 just would not make any sense to. It is included in this class and
138 in this documentation to facilitate subclassing of this class for
139 your own needs. If you desire to clear the results, then you can
140 simply call "setResults" with no argument.
141 visit ($tree)
143 The "visit" method accepts a Tree::Simple and applies the function
144 set in "new" or "setNodeFilter" appropriately. The results of this
145 application can be retrieved with "getResults"
146
148 These constants are part of the old-style interface, and therefore will
149 eventually be deprecated.
150 RECURSIVE
152 If passed this constant in the constructor, the function will be
153 applied recursively down the hierarchy of Tree::Simple objects.
154 CHILDREN_ONLY
156 If passed this constant in the constructor, the function will be
157 applied to the immediate children of the Tree::Simple object.
158
160 None that I am aware of. The code is pretty thoroughly tested (see CODE
161 COVERAGE section in Tree::Simple) and is based on an (non-publicly
162 released) module which I had used in production systems for about 2
163 years without incident. Of course, if you find a bug, let me know, and
164 I will be sure to fix it.
165
167 I have written a set of pre-built Visitor objects, available on CPAN as
168 Tree::Simple::VisitorFactory.
169
171 stevan little, <stevan@iinteractive.com>
172
174 <https://github.com/ronsavage/Tree-Simple>.
175
177 Copyright 2004-2006 by Infinity Interactive, Inc.
178 <http://www.iinteractive.com>
180 This library is free software; you can redistribute it and/or modify it
182 under the same terms as Perl itself.
183perl v5.30.1 2020-01-30 Tree::Simple::Visitor(3)