Страницы справочника OS X

Эта страница руководства для  версии 10.9 Mac OS X

Читать страницы руководства

Eval::Closure(3)                     User Contributed Perl Documentation                    Eval::Closure(3)



NAME
       Eval::Closure - safely and cleanly create closures via string eval

VERSION
       version 0.06

SYNOPSIS
         use Eval::Closure;

         my $code = eval_closure(
             source      => 'sub { $foo++ }',
             environment => {
                 '$foo' => \1,
             },
         );

         warn $code->(); # 1
         warn $code->(); # 2

         my $code2 = eval_closure(
             source => 'sub { $code->() }',
         ); # dies, $code isn't in scope

DESCRIPTION
       String eval is often used for dynamic code generation. For instance, "Moose" uses it heavily, to
       generate inlined versions of accessors and constructors, which speeds code up at runtime by a
       significant amount. String eval is not without its issues however - it's difficult to control the
       scope it's used in (which determines which variables are in scope inside the eval), and it can be
       quite slow, especially if doing a large number of evals.

       This module attempts to solve both of those problems. It provides an "eval_closure" function, which
       evals a string in a clean environment, other than a fixed list of specified variables. It also caches
       the result of the eval, so that doing repeated evals of the same source, even with a different
       environment, will be much faster (but note that the description is part of the string to be evaled,
       so it must also be the same (or non-existent) if caching is to work properly).

FUNCTIONS
   eval_closure(%args)
       This function provides the main functionality of this module. It is exported by default. It takes a
       hash of parameters, with these keys being valid:

       source
           The string to be evaled. It should end by returning a code reference. It can access any variable
           declared in the "environment" parameter (and only those variables). It can be either a string, or
           an arrayref of lines (which will be joined with newlines to produce the string).

       environment
           The environment to provide to the eval. This should be a hashref, mapping variable names
           (including sigils) to references of the appropriate type. For instance, a valid value for
           environment would be "{ '@foo' => [] }" (which would allow the generated function to use an array
           named @foo). Generally, this is used to allow the generated function to access externally defined
           variables (so you would pass in a reference to a variable that already exists).

       description
           This lets you provide a bit more information in backtraces. Normally, when a function that was
           generated through string eval is called, that stack frame will show up as "(eval n)", where 'n'
           is a sequential identifier for every string eval that has happened so far in the program. Passing
           a "description" parameter lets you override that to something more useful (for instance, Moose
           overrides the description for accessors to something like "accessor foo at MyClass.pm, line
           123").

       line
           This lets you override the particular line number that appears in backtraces, much like the
           "description" option. The default is 1.

       terse_error
           Normally, this function appends the source code that failed to compile, and prepends some
           explanatory text. Setting this option to true suppresses that behavior so you get only the
           compilation error that Perl actually reported.

BUGS
       No known bugs.

       Please report any bugs through RT: email "bug-eval-closure at rt.cpan.org", or browse to
       http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Eval-Closure
       <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Eval-Closure>.

SUPPORT
       You can find this documentation for this module with the perldoc command.

           perldoc Eval::Closure

       You can also look for information at:

       •   AnnoCPAN: Annotated CPAN documentation

           http://annocpan.org/dist/Eval-Closure <http://annocpan.org/dist/Eval-Closure>

       •   CPAN Ratings

           http://cpanratings.perl.org/d/Eval-Closure <http://cpanratings.perl.org/d/Eval-Closure>

       •   RT: CPAN's request tracker

           http://rt.cpan.org/NoAuth/Bugs.html?Dist=Eval-Closure
           <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Eval-Closure>

       •   Search CPAN

           http://search.cpan.org/dist/Eval-Closure <http://search.cpan.org/dist/Eval-Closure>

AUTHOR
       Jesse Luehrs <doy at tozt dot net>

       Based on code from Class::MOP::Method::Accessor, by Stevan Little and the Moose Cabal.

SEE ALSO
       •   Class::MOP::Method::Accessor

           This module is a factoring out of code that used to live here

COPYRIGHT AND LICENSE
       This software is copyright (c) 2011 by Jesse Luehrs.

       This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
       programming language system itself.



perl v5.12.5                                     2011-06-05                                 Eval::Closure(3)