-
-
22 Sep 2021 15:33:26 UTC
- Distribution: Const-Exporter
- Module version: v1.2.1
- Source (raw)
- Browse (raw)
- Changes
- How to Contribute
- Repository
- Issues
- Testers
- Kwalitee
Bus factor: 1- 92.20% Coverage
- License: artistic_2
- Perl: v5.10.0
- Activity
24 month- Tools
- Download (20.61KB)
- MetaCPAN Explorer
- Permissions
- Subscribe to distribution
- Permalinks
- This version
- Latest version
Looking for help!
The maintainer of this distribution is looking for people to help them improve this module! If you're interested then please contact them via email.- NAME
- VERSION
- SYNOPSIS
- DESCRIPTION
- KNOWN ISSUES
- SEE ALSO
- SOURCE
- BUGS
- AUTHOR
- CONTRIBUTORS
- COPYRIGHT AND LICENSE
NAME
Const::Exporter - Declare constants for export.
VERSION
version v1.2.1
SYNOPSIS
Define a constants module:
package MyApp::Constants; our $zoo => 1234; use Const::Exporter tag_a => [ # use MyApp::Constants /:tag_a/; 'foo' => 1, # exports "foo" '$bar' => 2, # exports "$bar" '@baz' => [qw/ a b c /], # exports "@baz" '%bo' => { a => 1 }, # exports "%bo" ], tag_b => [ # use MyApp::Constants /:tag_b/; 'foo', # exports "foo" (same as from ":tag_a") '$zoo', # exports "$zoo" (as defined above) ]; # `use Const::Exporter` can be specified multiple times use Const::Exporter tag_b => [ # we can add symbols to ":tab_b" 'moo' => $bar, # exports "moo" (same value as "$bar") ], enums => [ [qw/ goo gab gub /] => 0, # exports enumerated symbols, from 0..2 ], default => [qw/ foo $bar /]; # exported by default
and use that module:
package MyApp; use MyApp::Constants qw/ $zoo :tag_a /; ...
Dynamically Creating Constants
You may also import a predefined hash of constants for exporting dynamically:
use Const::Exporter; my %myconstants = ( 'foo' => 1, '$bar' => 2, '@baz' => [qw/ a b c /], '%bo' => { a => 1 }, ); # ... do stuff Const::Exporter->import( constants => [%myconstants], # define constants for exporting default => [ keys %myconstants ], # export everything in %myconstants by default );
DESCRIPTION
This module allows you to declare constants that can be exported to other modules.
To declare constants, simply group then into export tags:
package MyApp::Constants; use Const::Exporter tag_a => [ 'foo' => 1, 'bar' => 2, ], tag_b => [ 'baz' => 3, 'bar', ], default => [ 'foo', ];
Constants in the
default
tag are exported by default (that is, they are added to the@EXPORTS
array).When a constant is already defined in a previous tag, then no value is specified for it. (For example,
bar
intab_b
above.) If you do give a value, Const::Exporter will assume it's another symbol.Your module can include multiple calls to
use Const::Exporter
, so that you can reference constants in other expressions, e.g.use Const::Exporter tag => [ '$zero' => 0, ]; use Const::Exporter tag => [ '$one' => 1 + $zero, ];
or even something more complex:
use Const::Exporter http_ports => [ 'HTTP' => 80, 'HTTP_ALT' => 8080, 'HTTPS' => 443, ]; use Const::Exporter http_ports => [ '@HTTP_PORTS' => [ HTTP, HTTP_ALT, HTTPS ], ];
Constants can include traditional constant symbols, as well as scalars, arrays or hashes.
Constants can include values defined elsewhere in the code, e.g.
our $foo; BEGIN { $foo = calculate_value_for_constant(); } use Const::Exporter tag => [ '$foo' ];
Note that this will make the symbol read-only. You don't need to explicitly declare it as such.
Enumerated constants are also supported:
use Const::Exporter tag => [ [qw/ foo bar baz /] => 1, ];
will define the symbols
foo
(1),bar
(2) andbaz
(3).You can also specify a list of numbers, if you want to skip values:
use Const::Exporter tag => [ [qw/ foo bar baz /] => [1, 4], ];
will define the symbols
foo
(1),bar
(4) andbaz
(5).You can even specify string values:
use Const::Exporter tag => [ [qw/ foo bar baz /] => [qw/ feh meh neh /], ];
however, this is equivalent to
use Const::Exporter tag => [ 'foo' => 'feh', 'bar' => 'meh', 'baz' => 'neh', ];
Objects are also supported,
use Const::Exporter tag => [ '$foo' => Something->new( 123 ), ];
Export Tags
By default, all symbols are exportable (in
@EXPORT_OK
.)The
:default
tag is the same as not specifying any exports.The
:all
tag exports all symbols.KNOWN ISSUES
Support for older Perl versions
This module requires Perl v5.10 or newer.
Pull requests to support older versions of Perl are welcome. See "SOURCE".
Exporting Functions
Const::Exporter is not intended for use with modules that also export functions.
There are workarounds that you can use, such as getting Const::Exporter to export your functions, or munging
@EXPORT
etc. separately, but these are not supported and changes in the future my break our code.Mixing POD with Tags
The following code is a syntax error, at least with some versions of Perl:
use Const::Exporter =head2 a =cut a => [ foo => 1 ], =head2 b =cut b => [ bar => 2 ];
If you want to mix POD with your declarations, use multiple use lines, e.g.
=head2 a =cut use Const::Exporter a => [ foo => 1 ]; =head2 b =cut use Const::Exporter b => [ bar => 2 ];
SEE ALSO
See Exporter for a discussion of export tags.
Similar Modules
- Exporter::Constants
-
This module only allows you to declare function symbol constants, akin to the constant module, without tags.
- Constant::Exporter
-
This module only allows you to declare function symbol constants, akin to the constant module, although you can specify tags.
- Constant::Export::Lazy
-
This module only allows you to declare function symbol constants, akin to the constant module by defining functions that are only called as needed. The interface is rather complex.
- Const::Fast::Exporter
-
This module will export all constants declared in the package's namespace.
SOURCE
The development version is on github at https://github.com/robrwo/Const-Exporter and may be cloned from git://github.com/robrwo/Const-Exporter.git
BUGS
Please report any bugs or feature requests on the bugtracker website https://github.com/robrwo/Const-Exporter/issues
When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.
AUTHOR
Robert Rothenberg <rrwo@cpan.org>
CONTRIBUTORS
Slaven Rezić <slaven@rezic.de>
B. Estrade <estrabd@cpan.org>
COPYRIGHT AND LICENSE
This software is Copyright (c) 2014-2021 by Robert Rothenberg.
This is free software, licensed under:
The Artistic License 2.0 (GPL Compatible)
Module Install Instructions
To install Const::Exporter, copy and paste the appropriate command in to your terminal.
cpanm Const::Exporter
perl -MCPAN -e shell install Const::Exporter
For more information on module installation, please visit the detailed CPAN module installation guide.