1Eval::Closure(3) User Contributed Perl Documentation Eval::Closure(3)
2
6 Eval::Closure - safely and cleanly create closures via string eval
7
9 version 0.05
10
12 use Eval::Closure;
13 my $code = eval_closure(
15 source => 'sub { $foo++ }',
16 environment => {
17 '$foo' => \1,
18 },
19 );
20 warn $code->(); # 1
22 warn $code->(); # 2
23 my $code2 = eval_closure(
25 source => 'sub { $code->() }',
26 ); # dies, $code isn't in scope
27
29 String eval is often used for dynamic code generation. For instance,
30 "Moose" uses it heavily, to generate inlined versions of accessors and
31 constructors, which speeds code up at runtime by a significant amount.
32 String eval is not without its issues however - it's difficult to
33 control the scope it's used in (which determines which variables are in
34 scope inside the eval), and it can be quite slow, especially if doing a
35 large number of evals.
36 This module attempts to solve both of those problems. It provides an
38 "eval_closure" function, which evals a string in a clean environment,
39 other than a fixed list of specified variables. It also caches the
40 result of the eval, so that doing repeated evals of the same source,
41 even with a different environment, will be much faster (but note that
42 the description is part of the string to be evaled, so it must also be
43 the same (or non-existent) if caching is to work properly).
44
46 eval_closure(%args)
47 This function provides the main functionality of this module. It is
48 exported by default. It takes a hash of parameters, with these keys
49 being valid:
50 source
52 The string to be evaled. It should end by returning a code
53 reference. It can access any variable declared in the "environment"
54 parameter (and only those variables). It can be either a string, or
55 an arrayref of lines (which will be joined with newlines to produce
56 the string).
57 environment
59 The environment to provide to the eval. This should be a hashref,
60 mapping variable names (including sigils) to references of the
61 appropriate type. For instance, a valid value for environment would
62 be "{ '@foo' => [] }" (which would allow the generated function to
63 use an array named @foo). Generally, this is used to allow the
64 generated function to access externally defined variables (so you
65 would pass in a reference to a variable that already exists).
66 description
68 This lets you provide a bit more information in backtraces.
69 Normally, when a function that was generated through string eval is
70 called, that stack frame will show up as "(eval n)", where 'n' is a
71 sequential identifier for every string eval that has happened so
72 far in the program. Passing a "description" parameter lets you
73 override that to something more useful (for instance, Moose
74 overrides the description for accessors to something like "accessor
75 foo at MyClass.pm, line 123").
76 line
78 This lets you override the particular line number that appears in
79 backtraces, much like the "description" option. The default is 1.
80 terse_error
82 Normally, this function appends the source code that failed to
83 compile, and prepends some explanatory text. Setting this option to
84 true suppresses that behavior so you get only the compilation error
85 that Perl actually reported.
86
88 No known bugs.
89 Please report any bugs through RT: email "bug-eval-closure at
91 rt.cpan.org", or browse to
92 http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Eval-Closure
93 <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Eval-Closure>.
94
96 You can find this documentation for this module with the perldoc
97 command.
98 perldoc Eval::Closure
100 You can also look for information at:
102 · AnnoCPAN: Annotated CPAN documentation
104 http://annocpan.org/dist/Eval-Closure
106 <http://annocpan.org/dist/Eval-Closure>
107 · CPAN Ratings
109 http://cpanratings.perl.org/d/Eval-Closure
111 <http://cpanratings.perl.org/d/Eval-Closure>
112 · RT: CPAN's request tracker
114 http://rt.cpan.org/NoAuth/Bugs.html?Dist=Eval-Closure
116 <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Eval-Closure>
117 · Search CPAN
119 http://search.cpan.org/dist/Eval-Closure
121 <http://search.cpan.org/dist/Eval-Closure>
122
124 Jesse Luehrs <doy at tozt dot net>
125 Based on code from Class::MOP::Method::Accessor, by Stevan Little and
127 the Moose Cabal.
128
130 · Class::MOP::Method::Accessor
131 This module is a factoring out of code that used to live here
133
135 This software is copyright (c) 2011 by Jesse Luehrs.
136 This is free software; you can redistribute it and/or modify it under
138 the same terms as the Perl 5 programming language system itself.
139perl v5.12.3 2011-04-25 Eval::Closure(3)