Params-Smart - README

NAME

Params::Smart - use both positional and named arguments in a subroutine

REQUIREMENTS

The following non-core modules are required:

Regexp::Common

INSTALLATION

Installation can be done using the traditional Makefile.PL or the newer Build.PL methods.

Using Makefile.PL:

      perl Makefile.PL
      make test
      make install

(On Windows platforms you should use `nmake' instead.)

Using Build.PL (if you have Module::Build installed):

      perl Build.PL
      perl Build test
      perl Build install

SYNOPSIS

use Params::Smart 0.04;

      sub my_sub {
        %args = Params(qw( foo bar ?bo ?baz ))->args(@_);
        ...
      }

      my_sub( foo=> 1, bar=>2, bo=>3 );  # call with named arguments

      my_sub(1, 2, 3);                   # same, with positional args

DESCRIPTION

This module provides "smart" parameter handling for subroutines without having to use a changed syntax or source filters. Features include:

Mixed use of named and positional parameters.
Type checking and coercion through callbacks.
Dyanmic parameters configured from callbacks.
Memoization of parameter templates.

Compatability with Previous Versions

Note that the formatting for simple parameter templates has changed since version 0.03, and the complex parameter templates were not implemented until version 0.04, so it is best to specify a minimum version in use statements

use Params::Smart 0.04;

REVISION HISTORY

A brief list of changes since the previous release:

0.08 Wed Mar 21 2007

added case where undef value used in positional parameter
(thanks to Rick Westerman)
minor reorganization of POD

For a detailed history see the Changes file included in this distribution.

CAVEATS

Because Perl5 treats hashes as lists, this module attempts to interpret the arguments as a hash of named parameters first. If some hash keys match, and some do not, then it assumes there has been an error. If no keys match, then it assumes that it the arguments are positional.

In theory one can pass positional arguments where every other argument matches a hash key, or one can pass a hash with the wrong keys (possible if one copies/pastes code from the wrong call) and so it is treated as a positional argument.

This is probably uncommon for most data, but subroutines should take extra care to check if values are within allowed ranges. There may even be security issues if users can blindly specify data that they know can cause this confusion. If the application is critical enough, then this may not be an appropriate module to use (at least not until the ability to distinguish between lists and hashes is improved).

To diagnose potential bugs, or to enforce named or positional calling one can check the _named parameter.

A future version might make use of Perl internals to get around this problem.

SEE ALSO

This module is superficially similar in function to Getargs::Mixed but does not require named parameters to have an initial dash ('-').

Class::NamedParams provides a framework for implementing named parameters in classes.

Sub::NamedParams will create a named-parameter wrapper around subroutines which use positional parameters.

The syntax of the parameter templates is inspired by Perl6::Subs, though not necessarily compatible. (See also Apocalypse 6 in Perl6::Bible).

Sub::Usage inspired the error-messages returned by calls to arg().

Params::Validate is useful for (additional) parameter validation beyond what this module is capable of.

Class::ParmList provides a framework for parameter validation as well.

AUTHOR

Robert Rothenberg <rrwo at cpan.org>

Suggestions and Bug Reporting

Feedback is always welcome. Please use the CPAN Request Tracker at http://rt.cpan.org to submit bug reports.

LICENSE