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:
- •
- 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) 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.