Utilities:Modules:Class::ParmList

Class::ParmList

Class::ParmList is a general named parameter list parser. Handles default values, required vs allowed distinctions, optional name lexical checking, multiple retrieval, and error reporting. Works well as a complement to Class::NamedParms.

You can download the tarred and gzipped Perl Class-ParmList-1.03.tar.gz module here. It is 100% Perl.


POD Documentation


NAME

Class::ParmList - A collection of routines for processing named parameter lists for method calls.


SYNOPSIS

  use Class::ParmList qw(simple_parms parse_parms);
 $thingy->some_method({
      -bgcolor   => '#ff0000',
      -textcolor => '#000000'
          });
 sub some_method {
     my ($self) = shift;
         my ($parm_ref) = @_;
     my $parms = Class::ParmList->new ({
            -parms    => $parm_ref,
            -legal    => [qw (-textcolor -border -cellpadding)],
            -required => [qw (-bgcolor)],
            -defaults => {
                           -bgcolor   => "#ffffff",
                           -textcolor => "#000000"
                         }
         });
     if (not defined $parms) {
            my $error_message = Class::ParmList->error;
                die ($error_message);
     }
     # Stuff...
 }
  sub another_method {
    my $self = shift;
    my ($name,$rank,$serial_number) = simple_parms([qw(-name -rank -serial_number)], @_);
    #...
  }
  sub still_another {
     my $parms = parse_parms ({
            -parms    => \@_,
            -legal    => [qw (-textcolor -border -cellpadding)],
            -required => [qw (-bgcolor)],
            -defaults => {
                           -bgcolor   => "#ffffff",
                           -textcolor => "#000000"
                         }
         });
     if (not defined $parms) {
            my $error_message = Class::ParmList->error;
                die ($error_message);
     }
     # ...
  }

DESCRIPTION

This is a simple package for validating calling parameters to a subroutine or method. It allows you to use ``named parameters'' while providing checking for number and naming of parameters for verifying inputs are as expected and meet any minimum requirements. It also allows the setting of default values for the named parameters if omitted.


CHANGES

 1.00 1999.06.16 - Initial release
 1.01 1999.06.18 - Performance tweaks
 1.02 1999.06.21 - Fixing of failure to catch undeclared parm,
                   removal of 'use attrs qw(method)', and
                                   extension of 'make test' support.
 1.03 2000.12.06 - Added exportable class functions 'simple_parms'
                   and 'parse_parms' and allowed 'stacking' references
                   for parms to the object to improve calling usage.

METHODS

new($parm_list_ref);

Returns a reference to an object that can be used to return values. If an improper specification is passed, returns 'undef'. Otherwise returns the reference.

Example:

     my $parms = Class::ParmList->new ({
            -parms    => $parm_ref,
            -legal    => [qw (-textcolor -border -cellpadding)],
            -required => [qw (-bgcolor)],
            -defaults => {
                           -bgcolor   => "#ffffff",
                           -textcolor => "#000000"
                         }
         });
All four parameters (-parms, -legal, -required, and -defaults) are
optional. It is liberal in that anything defined for a -default
or -required is automatically added to the '-legal' list.

If the '-legal' parameter is not _explicitly_ called out, no checking against the legal list is done. If it _is_ explicitly called out, then all -parms are checked against it and it will fail with an error if a -parms parameter is present but not defined in the -legal explict or implict definitions.

To simplify calling routines, the '-parms' parameters is allowed to 'stack' anon list references: [['parm','value']]

This gives a calling routine the ability to parse @_ without jumping through hoops to handle the cases of arrays vs hashes for the passed parameters.

Example:

 sub example_sub {
   my $parms = Class::ParmList->new({ -parms => \@_,
                                     -legal => [],
                                  -required => ['-file','-data'],
                                  -defaults => {},
                                  });
   #...
 }

This routine would accept *either*

   example_sub({ '-file' => 'test', '-data' => 'stuff' });

or

   example_sub( '-file' => 'test', '-data' => 'stuff' );

with no code changes.

parse_parms($parm_list_ref);

This is a functional equivalent to the 'new' method. Calling parameters are identical, but it is called as a function that may be exported.

Example:

   my $parms = parse_parms({ -parms => \@_,
                             -legal => [],
                          -required => ['-file','-data'],
                          -defaults => {},
                         });
get($parm_name1,$parm_name2,...);

Returns the parameter value(s) specified in the call line. If a parameter is not defined, it returns undef. If a set of '-legal' parameters were declared, it croaks if a parameter not in the '-legal' set is asked for.

Example: my ($help,$who) = $parms->get(-help,-who);

exists($parm_name);

Returns true if the parameter specifed by $parm_name (qv. has been initialized), false if it does not exist.

  if ($parms->exists(-help) {
      # do stuff
  }
list_parms;

Returns the list of parameter names. (Names are always presented in lowercase).

Example:

  my (@parm_names) = $parms->list_parms;
all_parms;

Returns an anonymous hash containing all the currently set keys and values. This hash is suitable for usage with Class::NamedParms or Class::ParmList for setting keys/values. It works by making a shallow copy of the data. This means that it copies the scalar values. In the case of simple numbers and strings, this produces a new copy, in the case of references to hashes and arrays or objects, it returns the references to the original objects.

Example:

  my $parms = $parms->all_parms;

FUNCTIONS

error;

Returns the error message for the most recent invokation of 'new'. (Static method - does not require an object to function)

Example:

     my $error_message = Class::ParmList->error;
     die ($error_message);
simple_parms(['-list','-of','-parameter_names'],@_);

Parses the passed named parameter list (croaking/confessing if extra or missing parameters are found).

Examples:

 use Class::ParmList qw(simple_parms);
 sub some_method {
    my $self = shift;
    my ($name,$rank) = simple_parms([qw(-name -rank)],@_);
    # Now do stuff
 }
 sub some_function {
    my $serial_number = simple_parms([qw(-serial_number)],@_);
    # Now do stuff
 }

The passed parameter values for parsing this way may be either an anonymous hash of parameters

Example: a_function({ -parm1_name => $parm1_value, -parm2_name => $parm2_value }) )

or a straight list of parameters:

Example: a_function(-parm1_name => $parm1_value, -parm2_name => $parm2_value) )

Note that it *IS* legal for a parameter to be passed with an 'undef' value - it will not trigger an error.

If you need optional parameters, this function is not well suited. You should use the object methods above instead for that case - they are much more flexible (but quite a bit slower and slightly more complex to use).

Its main virtues are that is is simple to use, has rugged error checking for mis-usages and is reasonably fast.

'simple_parms' can be exported by specifying it on the 'use' line.


VERSION

1.03 2000.12.06


COPYRIGHT

Copyright 1999,2000 Benjamin Franz (<URL:http://www.nihongo.org/snowhare/>) and FreeRun Technologies, Inc. (<URL:http://www.freeruntech.com/>). All Rights Reserved. This software may be copied or redistributed under the same terms as Perl itelf.


AUTHOR

Benjamin Franz


TODO

Everything.