phpman > perldoc > Eval::Closure(3pm)

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

VERSION
    version 0.14

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
    *   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>

    *   Github

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

    *   RT: CPAN's request tracker

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

    *   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 AT tozt.net>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2016 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.