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Man Pages


Manual Reference Pages  -  SYMBOL::UTIL (3)

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NAME

Symbol::Util - Additional utils for Perl symbols manipulation

CONTENTS

SYNOPSIS



  use Symbol::Util :all;

  my $caller = caller;
  *{ fetch_glob("${caller}::foo") } = sub { "this is foo" };
  my $coderef = fetch_glob("${caller}::bar", "CODE");
  sub baz { 42; }
  export_glob($caller, "baz");

  print join "\n", keys %{ stash("main") };

  delete_glob("${caller}::foo", "CODE");

  use constant PI => 3.14159265;
  delete_sub "PI";   # remove constant from public API

  require YAML;
  export_package(__PACKAGE__, "YAML", "Dump");   # import YAML::Dump
  unexport_package(__PACKAGE, "YAML");   # remove imported symbols

  no Symbol::Util;   # clean all symbols imported from Symbol::Util



DESCRIPTION

This module provides a set of additional functions useful for Perl symbols manipulation.

All Perl symbols from the same package are organized as a stash. Each symbol (glob) contains one or more of following slots: SCALAR, ARRAY, HASH, CODE, IO, FORMAT. These slots are also accessible as standard variables or bare words.

The Perl symbols table is directly accessible with typeglob prefix but it can be difficult to read and problematic if strict mode is used. Also the access to stash, glob and one of its slot have different syntax notation.

stash and fetch_glob functions gets stash or glob without need to use no strict refs.

delete_glob function allows to delete specific slot of symbol name without deleting others.

delete_sub removes the symbol from class API. This symbol won’t be available as an object method.

export_glob function exports a glob to the target package.

export_package works like Exporter module and allows to export symbols from one package to other.

unexport_package allows to delete previously exported symbols.

USAGE

By default, the class does not export its symbols.
use Symbol::Util ’:all’; Imports all available symbols.
no Symbol::Util; Deletes all imported symbols from caller name space.

FUNCTIONS

stash( name : Str ) : HashRef Returns a reference to the stash for the specified name. If the stash does not already exist then it will be created. The name of the stash does not include the :: at the end. It is safe to use this function with use strict refs.



  print join "\n", keys %{ stash("main") };



fetch_glob( name : Str ) : GlobRef
fetch_glob( name : Str, slot : Str ) : Ref Returns a reference to the glob for the specified symbol name. If the symbol does not already exist then it will be created. If the symbol name is unqualified then it will be looked up in the calling package. It is safe to use this function with use strict refs.

If the slot argument is defined and this slot contains defined value, reference to this value is returned. The slot argument can be one of the following strings: SCALAR, ARRAY, HASH, CODE, IO, FORMAT).



  my $caller = caller;
  *{ fetch_glob("${caller}::foo") } = sub { "this is foo" };
  my $coderef = fetch_glob("${caller}::foo", "CODE");



list_glob_slots( name ) : Maybe[Array] Returns a list of slot names for glob with specified name which contain defined value. If the glob is undefined, the undef value is returned. If the glob is defined and has no defined slots, the empty list is returned.

The SCALAR slot is used only if it contains defined value.



  my $foo = 42;
  my @foo = (1, 2);
  sub foo { 1; };
  print join ",", list_glob_slots("foo");   # SCALAR,ARRAY,CODE



export_glob( target, name : Str ) : GlobRef
export_glob( target, name : Str, slots : Array ) : Ref Exports a glob name to the target package. Optionally exports only specified slots of the glob.



  sub my_function { ... };
  sub import {
      my $caller = caller;
      export_glob($caller, "my_function");
  }



delete_glob( name : Str, slots : Array[Str] ) : Maybe[GlobRef] Deletes the specified symbol name if slots are not specified, or deletes the specified slots in the symbol name (could be one or more of the following strings: SCALAR, ARRAY, HASH, CODE, IO, FORMAT).

Function returns the glob reference if there are any slots defined.



  our $FOO = 1;
  sub FOO { "bar" };

  delete_glob("FOO", "CODE");

  print $FOO;  # prints "1"
  FOO();       # error: sub not found



delete_sub( name : Str ) : Maybe[GlobRef] Deletes (or hides) the specified subroutine name from class API. It means that this subroutine will be no longer available as a class method. The purpose of this function is the same as namespace::clean pragma has: it cleans a package’s namespace from unwanted subroutines. Function doesn’t delete other slots than CODE slot of the glob.

Function returns the glob reference if there are any other slots still defined than <CODE> slot.



  package My::Class;

  use constant PI => 3.14159265;

  use Symbol::Util delete_sub;
  delete_sub "PI";   # remove constant from public API
  no Symbol::Util;   # remove also Symbol::Util::* from public API

  sub area {
      my ($self, $r) = @_;
      return PI * $r ** 2;
  }

  print My::Class->area(2);   # prints 12.5663706
  print My::Class->PI;        # Cant locate object method



export_package( target : Str, package : Str, names : Array[Str] ) : Bool
export_package( target : Str, package : Str, spec : HashRef, names : Array[Str] ) : Bool Exports symbols from package to target. If spec is defined as hash reference, it contains the specification for exporter. Otherwise the standard global variables of package are used (@EXPORT, @EXPORT_OK and %EXPORT_TAGS) to build the specification for exporter. The optional list of names defines an import list.

The spec is a reference to hash with following keys:
EXPORT Contains the list of default imports. It is the same as @EXPORT variable.
OK Contains the list of allowed imports. It is the same as @EXPORT_OK variable.
TAGS Contains the hash with tags. It is the same as %EXPORT_TAGS variable.

See Exporter documentation for explanation of these global variables and list of names.

The export_package function can export symbols from an external package to an external package. This function can also be used as a helper in import method.



  package My::Package;
  sub myfunc { };
  sub import {
      my ($package, @names) = @_;
      my $caller = caller();
      return export_package($caller, $package, {
          OK => [ qw( myfunc ) ],
      }, @names);
  };



All exported symbols are tracked and later can be removed with unexport_package function.

The function returns true value if there were no errors.

unexport_package( target : Str, package : Str ) : Bool Deletes symbols previously exported from package to target with export_package function. If the symbol was CODE reference it is deleted with delete_sub function. Otherwise it is deleted with delete_glob function with proper slot as an argument.

Deleting with delete_sub function means that this symbol is not available via class API as an object method.



  require YAML;
  export_package(__PACKAGE__, "YAML", "Dump");
  unexport_package(__PACKAGE__, "YAML");
  print Dump @INC;     # OK
  __PACKAGE__->Dump;   # Cant locate object method



This function can be used as a helper in unimport method.



  package My::Package;
  sub unimport {
      my ($package, @names) = @_;
      my $caller = caller();
      return unexport_package($caller, $package);
  };

  package main;
  use My::Package qw(something);
  no My::Package;
  main->something;   # Cant locate object method



The function returns true value if there were no errors.

SEE ALSO

Symbol, Sub::Delete, namespace::clean, Exporter.

BUGS

fetch_glob returns undef value if SCALAR slot contains undef value.

delete_glob and delete_sub delete SCALAR slot if it exists and contains undef value.

delete_glob and delete_sub always delete FORMAT slot.

If you find the bug or want to implement new features, please report it at <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Symbol-Util>

AUTHOR

Piotr Roszatycki <dexter@cpan.org>

LICENSE

Copyright (c) 2009, 2012 Piotr Roszatycki <dexter@cpan.org>.

This is free software; you can redistribute it and/or modify it under the same terms as perl itself.

See <http://dev.perl.org/licenses/artistic.html>

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perl v5.20.3 SYMBOL::UTIL (3) 2012-03-15

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