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 conveince 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 "normalised" 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 "normalised" 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 "normalised" 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 convience, 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 convience, 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 $integer
The _NONNEGINT
function is intended to be imported into your package, and provides a convenient way to test to see if a value is a non-negative integer (of any length). That is, a positive integer, or zero.
Returns the value as a convience, or undef
if the value is not a non-negative integer.
As with other tests that may return false values, care should be taken to test via "defined" in boolean validy contexts.
unless ( defined _NONNEGINT($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 apologise 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 existance (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
- Would be even nicer if someone would demonstrate how the hell to build a Module::Install dist of the ::Util dual Perl/XS type. :/
- 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
For other issues, contact the author.
AUTHOR
Adam Kennedy <adamk@cpan.org>
SEE ALSO
COPYRIGHT
Copyright 2005 - 2012 Adam Kennedy.
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.