# Module::Load::Conditional - man - phpman

## NAME
    [Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown) - Looking up module information / loading at runtime

## SYNOPSIS
        use [Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown) qw[can_load check_install requires];


        my $use_list = {
                CPANPLUS        => 0.05,
                LWP             => 5.60,
                '[Test::More](https://www.chedong.com/phpMan.php/perldoc/Test%3A%3AMore/markdown)'    => undef,
        };

        print can_load( modules => $use_list )
                ? 'all modules loaded successfully'
                : 'failed to load required modules';


        my $rv = check_install( module => 'LWP', version => 5.60 )
                    or print 'LWP is not installed!';

        print 'LWP up to date' if $rv->{uptodate};
        print "LWP version is $rv->{version}\n";
        print "LWP is installed as file $rv->{file}\n";


        print "LWP requires the following modules to be installed:\n";
        print join "\n", requires('LWP');

        ### allow [M::L::C](https://www.chedong.com/phpMan.php/perldoc/M%3A%3AL%3A%3AC/markdown) to peek in your %INC rather than just
        ### scanning @INC
        $[Module::Load::Conditional::CHECK_INC_HASH](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3ACHECKINCHASH/markdown) = 1;

        ### reset the 'can_load' cache
        undef $[Module::Load::Conditional::CACHE](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3ACACHE/markdown);

        ### don't have [Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown) issue warnings --
        ### default is '1'
        $[Module::Load::Conditional::VERBOSE](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3AVERBOSE/markdown) = 0;

        ### The last error that happened during a call to 'can_load'
        my $err = $[Module::Load::Conditional::ERROR](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3AERROR/markdown);

## DESCRIPTION
    [Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown) provides simple ways to query and possibly load any of the modules you
    have installed on your system during runtime.

    It is able to load multiple modules at once or none at all if one of them was not able to load.
    It also takes care of any error checking and so forth.

## Methods
  $href = check_install( module => NAME [, version => VERSION, verbose => BOOL ] );
    "check_install" allows you to verify if a certain module is installed or not. You may call it
    with the following arguments:

    module
        The name of the module you wish to verify -- this is a required key

    version
        The version this module needs to be -- this is optional

    verbose
        Whether or not to be verbose about what it is doing -- it will default to
        $[Module::Load::Conditional::VERBOSE](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3AVERBOSE/markdown)

    It will return undef if it was not able to find where the module was installed, or a hash
    reference with the following keys if it was able to find the file:

    file
        Full path to the file that contains the module

    dir Directory, or more exact the @INC entry, where the module was loaded from.

    version
        The version number of the installed module - this will be "undef" if the module had no (or
        unparsable) version number, or if the variable $[Module::Load::Conditional::FIND_VERSION](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3AFINDVERSION/markdown) was
        set to true. (See the "GLOBAL VARIABLES" section below for details)

    uptodate
        A boolean value indicating whether or not the module was found to be at least the version
        you specified. If you did not specify a version, uptodate will always be true if the module
        was found. If no parsable version was found in the module, uptodate will also be true, since
        "check_install" had no way to verify clearly.

        See also $[Module::Load::Conditional::DEPRECATED](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3ADEPRECATED/markdown), which affects the outcome of this value.

  $bool = can_load( modules => { NAME => VERSION [,NAME => VERSION] }, [verbose => BOOL, nocache => BOOL, autoload => BOOL] )
    "can_load" will take a list of modules, optionally with version numbers and determine if it is
    able to load them. If it can load *ALL* of them, it will. If one or more are unloadable, none
    will be loaded.

    This is particularly useful if you have More Than One Way (tm) to solve a problem in a program,
    and only wish to continue down a path if all modules could be loaded, and not load them if they
    couldn't.

    This function uses the "load" function or the "autoload_remote" function from [Module::Load](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad/markdown) under
    the hood.

    "can_load" takes the following arguments:

    modules
        This is a hashref of module/version pairs. The version indicates the minimum version to
        load. If no version is provided, any version is assumed to be good enough.

    verbose
        This controls whether warnings should be printed if a module failed to load. The default is
        to use the value of $[Module::Load::Conditional::VERBOSE](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3AVERBOSE/markdown).

    nocache
        "can_load" keeps its results in a cache, so it will not load the same module twice, nor will
        it attempt to load a module that has already failed to load before. By default, "can_load"
        will check its cache, but you can override that by setting "nocache" to true.

    autoload
        This controls whether imports the functions of a loaded modules to the caller package. The
        default is no importing any functions.

        See the "autoload" function and the "autoload_remote" function from [Module::Load](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad/markdown) for
        details.

  @list = requires( MODULE );
    "requires" can tell you what other modules a particular module requires. This is particularly
    useful when you're intending to write a module for public release and are listing its
    prerequisites.

    "requires" takes but one argument: the name of a module. It will then first check if it can
    actually load this module, and return undef if it can't. Otherwise, it will return a list of
    modules and pragmas that would have been loaded on the module's behalf.

    Note: The list "require" returns has originated from your current perl and your current install.

## Global Variables
    The behaviour of [Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown) can be altered by changing the following global
    variables:

  $[Module::Load::Conditional::VERBOSE](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3AVERBOSE/markdown)
    This controls whether [Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown) will issue warnings and explanations as to why
    certain things may have failed. If you set it to 0, [Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown) will not output
    any warnings. The default is 0;

  $[Module::Load::Conditional::FIND_VERSION](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3AFINDVERSION/markdown)
    This controls whether [Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown) will try to parse (and eval) the version from
    the module you're trying to load.

    If you don't wish to do this, set this variable to "false". Understand then that version
    comparisons are not possible, and [Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown) can not tell you what module version
    you have installed. This may be desirable from a security or performance point of view. Note
    that $FIND_VERSION code runs safely under "taint mode".

    The default is 1;

  $[Module::Load::Conditional::CHECK_INC_HASH](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3ACHECKINCHASH/markdown)
    This controls whether "[Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown)" checks your %INC hash to see if a module is
    available. By default, only @INC is scanned to see if a module is physically on your filesystem,
    or available via an "@INC-hook". Setting this variable to "true" will trust any entries in %INC
    and return them for you.

    The default is 0;

  $[Module::Load::Conditional::FORCE_SAFE_INC](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3AFORCESAFEINC/markdown)
    This controls whether "[Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown)" sanitises @INC by removing ""."". The current
    default setting is 0, but this may change in a future release.

  $[Module::Load::Conditional::CACHE](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3ACACHE/markdown)
    This holds the cache of the "can_load" function. If you explicitly want to remove the current
    cache, you can set this variable to "undef"

  $[Module::Load::Conditional::ERROR](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3AERROR/markdown)
    This holds a string of the last error that happened during a call to "can_load". It is useful to
    inspect this when "can_load" returns "undef".

  $[Module::Load::Conditional::DEPRECATED](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional%3A%3ADEPRECATED/markdown)
    This controls whether "[Module::Load::Conditional](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad%3A%3AConditional/markdown)" checks if a dual-life core module has been
    deprecated. If this is set to true "check_install" will return false to "uptodate", if a
    dual-life module is found to be loaded from $Config{privlibexp}

    The default is 0;

See Also
    "[Module::Load](https://www.chedong.com/phpMan.php/perldoc/Module%3A%3ALoad/markdown)"

## BUG REPORTS
    Please report bugs or other issues to <<bug-module-load-conditional@rt.cpan.org>>.

## AUTHOR
    This module by Jos Boumans <<kane@cpan.org>>.

## COPYRIGHT
    This library is free software; you may redistribute and/or modify it under the same terms as
    Perl itself.