| Eval::Closure(3pm) - phpMan
Eval::Closure(3pm) User Contributed Perl Documentation Eval::Closure(3pm)
NAME
Eval::Closure - safely and cleanly create closures via string eval
VERSION
version 0.11
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).
In perl 5.18 and greater, the environment hash can contain variables with a sigil of
"&". This will create a lexical sub in the evaluated code (see "The 'lexical_subs'
feature" in feature). Using a "&" sigil on perl versions before lexical subs were
available will throw an error.
alias
If set to true, the coderef returned closes over the variables referenced in the
environment hashref. (This feature requires Devel::LexAlias.) If set to false, the
coderef closes over a shallow copy of the variables.
If this argument is omitted, Eval::Closure will currently assume false, but this
assumption may change in a future version.
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 to GitHub Issues at https://github.com/doy/eval-closure/issues
<https://github.com/doy/eval-closure/issues>.
SEE ALSO
· Class::MOP::Method::Accessor
This module is a factoring out of code that used to live here
SUPPORT
You can find this documentation for this module with the perldoc command.
perldoc Eval::Closure
You can also look for information at:
· MetaCPAN
https://metacpan.org/release/Eval-Closure <https://metacpan.org/release/Eval-Closure>
· Github
https://github.com/doy/eval-closure <https://github.com/doy/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>
· CPAN Ratings
http://cpanratings.perl.org/d/Eval-Closure <http://cpanratings.perl.org/d/Eval-
Closure>
NOTES
Based on code from Class::MOP::Method::Accessor, by Stevan Little and the Moose Cabal.
AUTHOR
Jesse Luehrs <doy AT tozt.net>
COPYRIGHT AND LICENSE
This software is copyright (c) 2013 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 2013-07-30 Eval::Closure(3pm)
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