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Params::Util(3)	      User Contributed Perl Documentation      Params::Util(3)

NAME
       Params::Util - Simple, compact and correct param-checking functions

SYNOPSIS
	 # Import some functions
	 use Params::Util qw{_SCALAR _HASH _INSTANCE};

	 # If you are lazy, or need a lot of them...
	 use Params::Util ':ALL';

	 sub foo {
	     my	$object	 = _INSTANCE(shift, 'Foo') or return undef;
	     my	$image	 = _SCALAR(shift)	   or return undef;
	     my	$options = _HASH(shift)		   or return undef;
	     # etc...
	 }

DESCRIPTION
       "Params::Util" provides a basic set of importable functions that	makes
       checking	parameters a hell of a lot easier

       While they can be (and are) used	in other contexts, the main point
       behind this module is that the functions	both Do	What You Mean, and Do
       The Right Thing,	so they	are most useful	when you are getting params
       passed into your	code from someone and/or somewhere else	and you	can't
       really trust the	quality.

       Thus, "Params::Util" is of most use at the edges	of your	API, where
       params and data are coming in from outside your code.

       The functions provided by "Params::Util"	check in the most strictly
       correct manner known, are documented as thoroughly as possible so their
       exact behaviour is clear, and heavily tested so make sure they are not
       fooled by weird data and	Really Bad Things.

       To use, simply load the module providing	the functions you want to use
       as arguments (as	shown in the SYNOPSIS).

       To aid in maintainability, "Params::Util" will never export by default.

       You must	explicitly name	the functions you want to export, or use the
       ":ALL" param to just have it export everything (although	this is	not
       recommended if you have any _FOO	functions yourself with	which future
       additions to "Params::Util" may clash)

FUNCTIONS
   _STRING $string
       The "_STRING" function is intended to be	imported into your package,
       and provides a convenient way to	test to	see if a value is a normal
       non-false string	of non-zero length.

       Note that this will NOT do anything magic to deal with the special '0'
       false negative case, but	will return it.

	 # '0' not considered valid data
	 my $name = _STRING(shift) or die "Bad name";

	 # '0' is considered valid data
	 my $string = _STRING($_[0]) ? shift : die "Bad	string";

       Please also note	that this function expects a normal string. It does
       not support overloading or other	magic techniques to get	a string.

       Returns the string as a convenience if it is a valid string, or "undef"
       if not.

   _IDENTIFIER $string
       The "_IDENTIFIER" function is intended to be imported into your
       package,	and provides a convenient way to test to see if	a value	is a
       string that is a	valid Perl identifier.

       Returns the string as a convenience if it is a valid identifier,	or
       "undef" if not.

   _CLASS $string
       The "_CLASS" function is	intended to be imported	into your package, and
       provides	a convenient way to test to see	if a value is a	string that is
       a valid Perl class.

       This function only checks that the format is valid, not that the	class
       is actually loaded. It also assumes "normalized"	form, and does not
       accept class names such as "::Foo" or "D'Oh".

       Returns the string as a convenience if it is a valid class name,	or
       "undef" if not.

   _CLASSISA $string, $class
       The "_CLASSISA" function	is intended to be imported into	your package,
       and provides a convenient way to	test to	see if a value is a string
       that is a particularly class, or	a subclass of it.

       This function checks that the format is valid and calls the ->isa
       method on the class name. It does not check that	the class is actually
       loaded.

       It also assumes "normalized" form, and does not accept class names such
       as "::Foo" or "D'Oh".

       Returns the string as a convenience if it is a valid class name,	or
       "undef" if not.

   _CLASSDOES $string, $role
       This routine behaves exactly like "_CLASSISA", but checks with "->DOES"
       rather than "->isa".  This is probably only a good idea to use on Perl
       5.10 or later, when UNIVERSAL::DOES has been implemented.

   _SUBCLASS $string, $class
       The "_SUBCLASS" function	is intended to be imported into	your package,
       and provides a convenient way to	test to	see if a value is a string
       that is a subclass of a specified class.

       This function checks that the format is valid and calls the ->isa
       method on the class name. It does not check that	the class is actually
       loaded.

       It also assumes "normalized" form, and does not accept class names such
       as "::Foo" or "D'Oh".

       Returns the string as a convenience if it is a valid class name,	or
       "undef" if not.

   _NUMBER $scalar
       The "_NUMBER" function is intended to be	imported into your package,
       and provides a convenient way to	test to	see if a value is a number.
       That is,	it is defined and perl thinks it's a number.

       This function is	basically a Params::Util-style wrapper around the
       Scalar::Util "looks_like_number"	function.

       Returns the value as a convenience, or "undef" if the value is not a
       number.

   _POSINT $integer
       The "_POSINT" function is intended to be	imported into your package,
       and provides a convenient way to	test to	see if a value is a positive
       integer (of any length).

       Returns the value as a convenience, or "undef" if the value is not a
       positive	integer.

       The name	itself is derived from the XML schema constraint of the	same
       name.

   _NONNEGINT $integer
       The "_NONNEGINT"	function is intended to	be imported into your package,
       and provides a convenient way to	test to	see if a value is a non-
       negative	integer	(of any	length). That is, a positive integer, or zero.

       Returns the value as a convenience, or "undef" if the value is not a
       non-negative integer.

       As with other tests that	may return false values, care should be	taken
       to test via "defined" in	boolean	validly	contexts.

	 unless	( defined _NONNEGINT($value) ) {
	    die	"Invalid value";
	 }

       The name	itself is derived from the XML schema constraint of the	same
       name.

   _SCALAR \$scalar
       The "_SCALAR" function is intended to be	imported into your package,
       and provides a convenient way to	test for a raw and unblessed "SCALAR"
       reference, with content of non-zero length.

       For a version that allows zero length "SCALAR" references, see the
       "_SCALAR0" function.

       Returns the "SCALAR" reference itself as	a convenience, or "undef" if
       the value provided is not a "SCALAR" reference.

   _SCALAR0 \$scalar
       The "_SCALAR0" function is intended to be imported into your package,
       and provides a convenient way to	test for a raw and unblessed "SCALAR0"
       reference, allowing content of zero-length.

       For a simpler "give me some content" version that requires non-zero
       length, "_SCALAR" function.

       Returns the "SCALAR" reference itself as	a convenience, or "undef" if
       the value provided is not a "SCALAR" reference.

   _ARRAY $value
       The "_ARRAY" function is	intended to be imported	into your package, and
       provides	a convenient way to test for a raw and unblessed "ARRAY"
       reference containing at least one element of any	kind.

       For a more basic	form that allows zero length ARRAY references, see the
       "_ARRAY0" function.

       Returns the "ARRAY" reference itself as a convenience, or "undef" if
       the value provided is not an "ARRAY" reference.

   _ARRAY0 $value
       The "_ARRAY0" function is intended to be	imported into your package,
       and provides a convenient way to	test for a raw and unblessed "ARRAY"
       reference, allowing "ARRAY" references that contain no elements.

       For a more basic	"An array of something"	form that also requires	at
       least one element, see the "_ARRAY" function.

       Returns the "ARRAY" reference itself as a convenience, or "undef" if
       the value provided is not an "ARRAY" reference.

   _ARRAYLIKE $value
       The "_ARRAYLIKE"	function tests whether a given scalar value can
       respond to array	dereferencing.	If it can, the value is	returned.  If
       it cannot, "_ARRAYLIKE" returns "undef".

   _HASH $value
       The "_HASH" function is intended	to be imported into your package, and
       provides	a convenient way to test for a raw and unblessed "HASH"
       reference with at least one entry.

       For a version of	this function that allows the "HASH" to	be empty, see
       the "_HASH0" function.

       Returns the "HASH" reference itself as a	convenience, or	"undef"	if the
       value provided is not an	"HASH" reference.

   _HASH0 $value
       The "_HASH0" function is	intended to be imported	into your package, and
       provides	a convenient way to test for a raw and unblessed "HASH"
       reference, regardless of	the "HASH" content.

       For a simpler "A	hash of	something" version that	requires at least one
       element,	see the	"_HASH"	function.

       Returns the "HASH" reference itself as a	convenience, or	"undef"	if the
       value provided is not an	"HASH" reference.

   _HASHLIKE $value
       The "_HASHLIKE" function	tests whether a	given scalar value can respond
       to hash dereferencing.  If it can, the value is returned.  If it
       cannot, "_HASHLIKE" returns "undef".

   _CODE $value
       The "_CODE" function is intended	to be imported into your package, and
       provides	a convenient way to test for a raw and unblessed "CODE"
       reference.

       Returns the "CODE" reference itself as a	convenience, or	"undef"	if the
       value provided is not an	"CODE" reference.

   _CODELIKE $value
       The "_CODELIKE" is the more generic version of "_CODE". Unlike "_CODE",
       which checks for	an explicit "CODE" reference, the "_CODELIKE" function
       also includes things that act like them,	such as	blessed	objects	that
       overload	'&{}'.

       Please note that	in the case of objects overloaded with '&{}', you will
       almost always end up also testing it in 'bool' context at some stage.

       For example:

	 sub foo {
	     my	$code1 = _CODELIKE(shift) or die "No code param	provided";
	     my	$code2 = _CODELIKE(shift);
	     if	( $code2 ) {
		  print	"Got optional second code param";
	     }
	 }

       As such,	you will most likely always want to make sure your class has
       at least	the following to allow it to evaluate to true in boolean
       context.

	 # Always evaluate to true in boolean context
	 use overload 'bool' =>	sub () { 1 };

       Returns the callable value as a convenience, or "undef" if the value
       provided	is not callable.

       Note - This function was	formerly known as _CALLABLE but	has been
       renamed for greater symmetry with the other _XXXXLIKE functions.

       The use of _CALLABLE has	been deprecated. It will continue to work, but
       with a warning, until end-2006, then will be removed.

       I apologize for any inconvenience caused.

   _INVOCANT $value
       This routine tests whether the given value is a valid method invocant.
       This can	be either an instance of an object, or a class name.

       If so, the value	itself is returned.  Otherwise,	"_INVOCANT" returns
       "undef".

   _INSTANCE $object, $class
       The "_INSTANCE" function	is intended to be imported into	your package,
       and provides a convenient way to	test for an object of a	particular
       class in	a strictly correct manner.

       Returns the object itself as a convenience, or "undef" if the value
       provided	is not an object of that type.

   _INSTANCEDOES $object, $role
       This routine behaves exactly like "_INSTANCE", but checks with "->DOES"
       rather than "->isa".  This is probably only a good idea to use on Perl
       5.10 or later, when UNIVERSAL::DOES has been implemented.

   _REGEX $value
       The "_REGEX" function is	intended to be imported	into your package, and
       provides	a convenient way to test for a regular expression.

       Returns the value itself	as a convenience, or "undef" if	the value
       provided	is not a regular expression.

   _SET	\@array, $class
       The "_SET" function is intended to be imported into your	package, and
       provides	a convenient way to test for set of at least one object	of a
       particular class	in a strictly correct manner.

       The set is provided as a	reference to an	"ARRAY"	of objects of the
       class provided.

       For an alternative function that	allows zero-length sets, see the
       "_SET0" function.

       Returns the "ARRAY" reference itself as a convenience, or "undef" if
       the value provided is not a set of that class.

   _SET0 \@array, $class
       The "_SET0" function is intended	to be imported into your package, and
       provides	a convenient way to test for a set of objects of a particular
       class in	a strictly correct manner, allowing for	zero objects.

       The set is provided as a	reference to an	"ARRAY"	of objects of the
       class provided.

       For an alternative function that	requires at least one object, see the
       "_SET" function.

       Returns the "ARRAY" reference itself as a convenience, or "undef" if
       the value provided is not a set of that class.

   _HANDLE
       The "_HANDLE" function is intended to be	imported into your package,
       and provides a convenient way to	test whether or	not a single scalar
       value is	a file handle.

       Unfortunately, in Perl the definition of	a file handle can be a little
       bit fuzzy, so this function is likely to	be somewhat imperfect (at
       first anyway).

       That said, it is	implement as well or better than the other file	handle
       detectors in existence (and we stole from the best of them).

   _DRIVER $string
	 sub foo {
	   my $class = _DRIVER(shift, 'My::Driver::Base') or die "Bad driver";
	   ...
	 }

       The "_DRIVER" function is intended to be	imported into your package,
       and provides a convenient way to	load and validate a driver class.

       The most	common pattern when taking a driver class as a parameter is to
       check that the name is a	class (i.e. check against _CLASS) and then to
       load the	class (if it exists) and then ensure that the class returns
       true for	the isa	method on some base driver name.

       Return the value	as a convenience, or "undef" if	the value is not a
       class name, the module does not exist, the module does not load,	or the
       class fails the isa test.

TO DO
       - Add _CAN to help resolve the UNIVERSAL::can debacle

       - Implement an assertion-like version of	this module, that dies on
       error.

       - Implement a Test:: version of this module, for	use in testing

SUPPORT
       Bugs should be reported via the CPAN bug	tracker	at

       <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Params-Util>

AUTHOR
       Adam Kennedy <adamk AT cpan.org>

       Jens Rehsack <rehsack AT	cpan.org>

SEE ALSO
       Params::Validate

COPYRIGHT
       Copyright 2005 -	2012 Adam Kennedy.

       Copyright 2020 -	2020 Jens Rehsack.

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

       The full	text of	the license can	be found in the	LICENSE	file included
       with this module.

perl v5.32.1			  2020-11-02		       Params::Util(3)

NAME | SYNOPSIS | DESCRIPTION | FUNCTIONS | TO DO | SUPPORT | AUTHOR | SEE ALSO | COPYRIGHT

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