Params::Util - Simple, compact and correct param-checking functions
# 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...
}
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)
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.
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.
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.
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.
This routine behaves exactly like ["_CLASSISA"](#_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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
This routine behaves exactly like ["_INSTANCE"](#_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.
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.
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.
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.
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).
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.
- 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
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.
Adam Kennedy [email protected]
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.