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

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>.

SEE ALSO

       o   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:

       o   MetaCPAN

	   <https://metacpan.org/release/Eval-Closure>

       o   Github

	   <https://github.com/doy/eval-closure>

       o   RT: CPAN's request tracker

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

       o   CPAN Ratings

	   <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@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 v5.18.2							    2013-07-30							  Eval::Closure(3)