Eval::Closure(3pm) User Contributed Perl Documentation Eval::Closure(3pm)
NAME
Eval::Closure - safely and cleanly create closures via string eval
VERSION
version 0.08
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's easy to miss compilation errors,
since eval catches them and sticks them in $@ instead.
This module attempts to solve these problems. It provides an "eval_closure" function, which evals a string in a clean environment, other
than a fixed list of specified variables. Compilation errors are rethrown automatically.
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:
o AnnoCPAN: Annotated CPAN documentation
http://annocpan.org/dist/Eval-Closure <http://annocpan.org/dist/Eval-Closure>
o CPAN Ratings
http://cpanratings.perl.org/d/Eval-Closure <http://cpanratings.perl.org/d/Eval-Closure>
o 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>
o 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
o 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) 2012 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 v5.14.2 2012-02-09 Eval::Closure(3pm)