1Data::Visitor::CallbackU(s3e)r Contributed Perl DocumentaDtaitoan::Visitor::Callback(3)
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NAME

6       Data::Visitor::Callback - A Data::Visitor with callbacks.
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VERSION

9       version 0.30
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SYNOPSIS

12               use Data::Visitor::Callback;
13
14               my $v = Data::Visitor::Callback->new(
15                       # you can provide callbacks
16                       # $_ will contain the visited value
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18                       value => sub { ... },
19                       array => sub { ... },
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21
22                       # you can also delegate to method names
23                       # this specific example will force traversal on objects, by using the
24                       # 'visit_ref' callback which normally traverse unblessed references
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26                       object => "visit_ref",
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28
29                       # you can also use class names as callbacks
30                       # the callback will be invoked on all objects which inherit that class
31
32                       'Some::Class' => sub {
33                               my ( $v, $obj ) = @_; # $v is the visitor
34
35                               ...
36                       },
37               );
38
39               $v->visit( $some_perl_value );
40

DESCRIPTION

42       This is a Data::Visitor subclass that lets you invoke callbacks instead
43       of needing to subclass yourself.
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METHODS

46       new %opts, %callbacks
47           Construct a new visitor.
48
49           The options supported are:
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51           ignore_return_values
52               When this is true (off by default) the return values from the
53               callbacks are ignored, thus disabling the fmapping behavior as
54               documented in Data::Visitor.
55
56               This is useful when you want to modify $_ directly
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58           tied_as_objects
59               Whether ot not to visit the "tied" in perlfunc of a tied
60               structure instead of pretending the structure is just a normal
61               one.
62
63               See "visit_tied" in Data::Visitor.
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CALLBACKS

66       Use these keys for the corresponding callbacks.
67
68       The callback is in the form:
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70               sub {
71                       my ( $visitor, $data ) = @_;
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73                       # or you can use $_, it's aliased
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75                       return $data; # or modified data
76               }
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78       Within the callback $_ is aliased to the data, and this is also passed
79       in the parameter list.
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81       Any method can also be used as a callback:
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83               object => "visit_ref", # visit objects anyway
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85       visit
86           Called for all values
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88       value
89           Called for non objects, non container (hash, array, glob or scalar
90           ref) values.
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92       ref_value
93           Called after "value", for references to regexes, globs and code.
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95       plain_value
96           Called after "value" for non references.
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98       object
99           Called for blessed objects.
100
101           Since "visit_object" in Data::Visitor will not recurse downwards
102           unless you delegate to "visit_ref", you can specify "visit_ref" as
103           the callback for "object" in order to enter objects.
104
105           It is reccomended that you specify the classes (or base classes)
106           you want though, instead of just visiting any object forcefully.
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108       Some::Class
109           You can use any class name as a callback. This is colled only after
110           the "object" callback.
111
112           If the object "isa" the class then the callback will fire.
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114           These callbacks are called from least derived to most derived by
115           comparing the classes' "isa" at construction time.
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117       object_no_class
118           Called for every object that did not have a class callback.
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120       object_final
121           The last callback called for objects, useful if you want to post
122           process the output of any class callbacks.
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124       array
125           Called for array references.
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127       hash
128           Called for hash references.
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130       glob
131           Called for glob references.
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133       scalar
134           Called for scalar references.
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136       tied
137           Called on the return value of "tied" for all tied containers. Also
138           passes in the variable as the second argument.
139
140       seen
141           Called for a reference value encountered a second time.
142
143           Passes in the result mapping as the second argument.
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AUTHORS

146       ·   Yuval Kogman <nothingmuch@woobling.org>
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148       ·   Marcel Grünauer <marcel@cpan.org>
149

151       This software is copyright (c) 2013 by Yuval Kogman.
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153       This is free software; you can redistribute it and/or modify it under
154       the same terms as the Perl 5 programming language system itself.
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158perl v5.30.0                      2019-07-26        Data::Visitor::Callback(3)
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