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...
  }

CWParams::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, CWParams::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 CWParams::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, CWParams::Util will never export by default.

You must explicitly name the functions you want to export, or use the CW: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 CWParams::Util may clash)

The CW_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 CW'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 CWundef if not. The CW_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 CWundef if not. The CW_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 CW::Foo or CWD'Oh.

Returns the string as a convenience if it is a valid class name, or CWundef if not. The CW_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 CWundef if the value is not a positive integer.

The CW_SCALAR function is intended to be imported into your package, and provides a convenient way to test for a raw and unblessed CWSCALAR reference, with content of non-zero length.

For a version that allows zero length CWSCALAR references, see the CW_SCALAR0 function.

Returns the CWSCALAR reference itself as a convenience, or CWundef if the value provided is not a CWSCALAR reference.

The CW_SCALAR0 function is intended to be imported into your package, and provides a convenient way to test for a raw and unblessed CWSCALAR0 reference, allowing content of zero-length.

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

Returns the CWSCALAR reference itself as a convenience, or CWundef if the value provided is not a CWSCALAR reference. The CW_ARRAY function is intended to be imported into your package, and provides a convenient way to test for a raw and unblessed CWARRAY reference containing at least one element of any kind.

For a more basic form that allows zero length ARRAY references, see the CW_ARRAY0 function.

Returns the CWARRAY reference itself as a convenience, or CWundef if the value provided is not an CWARRAY reference. The CW_ARRAY0 function is intended to be imported into your package, and provides a convenient way to test for a raw and unblessed CWARRAY reference, allowing CWARRAY references that contain no elements.

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

Returns the CWARRAY reference itself as a convenience, or CWundef if the value provided is not an CWARRAY reference. The CW_HASH function is intended to be imported into your package, and provides a convenient way to test for a raw and unblessed CWHASH reference with at least one entry.

For a version of this function that allows the CWHASH to be empty, see the CW_HASH0 function.

Returns the CWHASH reference itself as a convenience, or CWundef if the value provided is not an CWHASH reference. The CW_HASH0 function is intended to be imported into your package, and provides a convenient way to test for a raw and unblessed CWHASH reference, regardless of the CWHASH content.

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

Returns the CWHASH reference itself as a convenience, or CWundef if the value provided is not an CWHASH reference. The CW_CODE function is intended to be imported into your package, and provides a convenient way to test for a raw and unblessed CWCODE reference.

Returns the CWCODE reference itself as a convenience, or CWundef if the value provided is not an CWCODE reference. The CW_CALLABLE is the more generic version of CW_CODE. Unlike CW_CODE, which checks for an explicit CWCODE reference, the CW_CALLABLE function also includes things that act like them, such as blessed objects that overload CW'&{}'.

Note that in the case of objects overloaded with '&{}', you will almost always end up also testing it in 'bool' context. As such, you will most often want to make sure your class has 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 CWundef if the value provided is not callable. The CW_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 CWundef if the value provided is not an object of that type. The CW_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 CWARRAY of objects of the class provided.

For an alternative function that allows zero-length sets, see the CW_SET0 function.

Returns the CWARRAY reference itself as a convenience, or CWundef if the value provided is not a set of that class. The CW_SET0 function is intended to be imported into your package, and provides a convenient way to test for 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 CWARRAY of objects of the class provided.

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

Returns the CWARRAY reference itself as a convenience, or CWundef if the value provided is not a set of that class.

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

- More comprehensive tests for _SET and _SET0

- Would be nice if someone would re-implement in XS for me? (donish)

- 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.

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 <cpan@ali.as>, <http://ali.as/>

Copyright 2005, 2006 Adam Kennedy. All rights reserved.

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.