1Package::Stash(3)     User Contributed Perl Documentation    Package::Stash(3)
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NAME

6       Package::Stash - Routines for manipulating stashes
7

VERSION

9       version 0.39
10

SYNOPSIS

12         my $stash = Package::Stash->new('Foo');
13         $stash->add_symbol('%foo', {bar => 1});
14         # $Foo::foo{bar} == 1
15         $stash->has_symbol('$foo') # false
16         my $namespace = $stash->namespace;
17         *{ $namespace->{foo} }{HASH} # {bar => 1}
18

DESCRIPTION

20       Manipulating stashes (Perl's symbol tables) is occasionally necessary,
21       but incredibly messy, and easy to get wrong. This module hides all of
22       that behind a simple API.
23
24       NOTE: Most methods in this class require a variable specification that
25       includes a sigil. If this sigil is absent, it is assumed to represent
26       the IO slot.
27
28       Due to limitations in the typeglob API available to perl code, and to
29       typeglob manipulation in perl being quite slow, this module provides
30       two implementations - one in pure perl, and one using XS. The XS
31       implementation is to be preferred for most usages; the pure perl one is
32       provided for cases where XS modules are not a possibility. The current
33       implementation in use can be set by setting
34       $ENV{PACKAGE_STASH_IMPLEMENTATION} or $Package::Stash::IMPLEMENTATION
35       before loading Package::Stash (with the environment variable taking
36       precedence), otherwise, it will use the XS implementation if possible,
37       falling back to the pure perl one.
38

METHODS

40   new $package_name
41       Creates a new "Package::Stash" object, for the package given as the
42       only argument.
43
44   name
45       Returns the name of the package that this object represents.
46
47   namespace
48       Returns the raw stash itself.
49
50   add_symbol $variable $value %opts
51       Adds a new package symbol, for the symbol given as $variable, and
52       optionally gives it an initial value of $value. $variable should be the
53       name of variable including the sigil, so
54
55         Package::Stash->new('Foo')->add_symbol('%foo')
56
57       will create %Foo::foo.
58
59       Valid options (all optional) are "filename", "first_line_num", and
60       "last_line_num".
61
62       $opts{filename}, $opts{first_line_num}, and $opts{last_line_num} can be
63       used to indicate where the symbol should be regarded as having been
64       defined.  Currently these values are only used if the symbol is a
65       subroutine ('"&"' sigil) and only if "$^P & 0x10" is true, in which
66       case the special %DB::sub hash is updated to record the values of
67       "filename", "first_line_num", and "last_line_num" for the subroutine.
68       If these are not passed, their values are inferred (as much as
69       possible) from "caller" information.
70
71   remove_glob $name
72       Removes all package variables with the given name, regardless of sigil.
73
74   has_symbol $variable
75       Returns whether or not the given package variable (including sigil)
76       exists.
77
78   get_symbol $variable
79       Returns the value of the given package variable (including sigil).
80
81   get_or_add_symbol $variable
82       Like "get_symbol", except that it will return an empty hashref or
83       arrayref if the variable doesn't exist.
84
85   remove_symbol $variable
86       Removes the package variable described by $variable (which includes the
87       sigil); other variables with the same name but different sigils will be
88       untouched.
89
90   list_all_symbols $type_filter
91       Returns a list of package variable names in the package, without
92       sigils. If a "type_filter" is passed, it is used to select package
93       variables of a given type, where valid types are the slots of a
94       typeglob ('SCALAR', 'CODE', 'HASH', etc). Note that if the package
95       contained any "BEGIN" blocks, perl will leave an empty typeglob in the
96       "BEGIN" slot, so this will show up if no filter is used (and similarly
97       for "INIT", "END", etc).
98
99   get_all_symbols $type_filter
100       Returns a hashref, keyed by the variable names in the package. If
101       $type_filter is passed, the hash will contain every variable of that
102       type in the package as values, otherwise, it will contain the typeglobs
103       corresponding to the variable names (basically, a clone of the stash).
104
105       This is especially useful for debuggers and profilers, which use
106       %DB::sub to determine where the source code for a subroutine can be
107       found.  See
108       <http://perldoc.perl.org/perldebguts.html#Debugger-Internals> for more
109       information about %DB::sub.
110

WORKING WITH VARIABLES

112       It is important to note, that when working with scalar variables, the
113       default behavior is to copy values.
114
115         my $stash = Package::Stash->new('Some::Namespace');
116         my $variable = 1;
117         # $Some::Namespace::name is a copy of $variable
118         $stash->add_symbol('$name', $variable);
119         $variable++
120         # $Some::Namespace::name == 1 , $variable == 2
121
122       This will likely confuse people who expect it to work the same as
123       typeglob assignment, which simply creates new references to existing
124       variables.
125
126         my $variable = 1;
127         {
128             no strict 'refs';
129             # assign $Package::Stash::name = $variable
130             *{'Package::Stash::name'} = \$variable;
131         }
132         $variable++ # affects both names
133
134       If this behaviour is desired when working with Package::Stash, simply
135       pass Package::Stash a scalar ref:
136
137         my $stash = Package::Stash->new('Some::Namespace');
138         my $variable = 1;
139         # $Some::Namespace::name is now $variable
140         $stash->add_symbol('$name', \$variable);
141         $variable++
142         # $Some::Namespace::name == 2 , $variable == 2
143
144       This will be what you want as well if you're ever working with Readonly
145       variables:
146
147         use Readonly;
148         Readonly my $value, 'hello';
149
150         $stash->add_symbol('$name', \$value); # reference
151         print $Some::Namespace::name; # hello
152         # Tries to modify the read-only 'hello' and dies.
153         $Some::Namespace::name .= " world";
154
155         $stash->add_symbol('$name', $value); # copy
156         print $Some::Namespace::name; # hello
157         # No problem, modifying a copy, not the original
158         $Some::Namespace::name .= " world";
159

SEE ALSO

161       •   Class::MOP::Package
162
163           This module is a factoring out of code that used to live here
164

HISTORY

166       Based on code from Class::MOP::Package, by Stevan Little and the Moose
167       Cabal.
168

BUGS / CAVEATS

170       •   Prior to perl 5.10, scalar slots are only considered to exist if
171           they are defined
172
173           This is due to a shortcoming within perl itself. See "Making
174           References" in perlref point 7 for more information.
175
176       •   GLOB and FORMAT variables are not (yet) accessible through this
177           module.
178
179       •   Also, see the BUGS section for the specific backends
180           (Package::Stash::XS and Package::Stash::PP)
181
182       Bugs may be submitted through the RT bug tracker
183       <https://rt.cpan.org/Public/Dist/Display.html?Name=Package-Stash> (or
184       bug-Package-Stash@rt.cpan.org <mailto:bug-Package-Stash@rt.cpan.org>).
185

AUTHORS

187       •   Stevan Little <stevan.little@iinteractive.com>
188
189       •   Jesse Luehrs <doy@tozt.net>
190

CONTRIBUTORS

192       •   Karen Etheridge <ether@cpan.org>
193
194       •   Carlos Lima <carlos@multi>
195
196       •   Dave Rolsky <autarch@urth.org>
197
198       •   Justin Hunter <justin.d.hunter@gmail.com>
199
200       •   Christian Walde <walde.christian@googlemail.com>
201
202       •   Kent Fredric <kentfredric@gmail.com>
203
204       •   Niko Tyni <ntyni@debian.org>
205
206       •   Renee <reb@perl-services.de>
207
208       •   Tim Bunce <Tim.Bunce@pobox.com>
209
211       This software is copyright (c) 2020 by Jesse Luehrs.
212
213       This is free software; you can redistribute it and/or modify it under
214       the same terms as the Perl 5 programming language system itself.
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218perl v5.34.0                      2021-07-22                 Package::Stash(3)
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