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Ubiquity of the CGI param method

by jwark (Novice)
on Aug 10, 2010 at 14:34 UTC ( #854059=perlquestion: print w/replies, xml ) Need Help??
jwark has asked for the wisdom of the Perl Monks concerning the following question:

I have been using the Data::FormValidator package and have found it to be quite helpful.

I have noticed that this package (and others) makes use of the CGI param() method to validate information *OR* it requires a object that has its own param() method that functions the same as the CGI param() method.

I was wondering if a package existed on CPAN that, when used, produces an object that simply has a param() method. My thoughts were that it would be leaner to use such a package for non-CGI type validation. You could simply load some parameters into it, and then use it with Data::FormValidator (or some other package requiring a param method).

Also, on the surface, the param method seems pretty straight forward to implement, but I am sure I will miss some edge cases which would just be annoying. Perhaps there is some sort of standards page that describes the way the CGI->param() method works, like an RFC.

In all honesty, I haven't used the Data::FormValidator without a CGI object yet, but the apparent usefulness of the param method indicates that there should be a simple package that gives you that method (in object form).

Any information leading to such a simple package/method would be greatly appreciated.

Replies are listed 'Best First'.
Re: Ubiquity of the CGI param method
by LTjake (Prior) on Aug 11, 2010 at 01:14 UTC

    I *think* I see where you're going with this. Basically you want arbitrary data structure validation.

    Typically people call the "profile" for such validation, a schema. You'll see that term most frequently with XML data.

    In the Perl world, there are no doubt a number of tools that let you validate data against a schema. One such tool is Data-Rx (homepage). One particularly nice feature is that the author has also prepared implementations in other languages, so the same schema can be used against a number of different end-points.

    Sorry for not directly answering your question, but I would feel silly if I didn't mention this existing tool.

    "Go up to the next female stranger you see and tell her that her "body is a wonderland."
    My hypothesis is that she’ll be too busy laughing at you to even bother slapping you.
    " (src)

Re: Ubiquity of the CGI param method
by skx (Parson) on Aug 11, 2010 at 08:22 UTC

    I'm not sure there's any information on building such a thing - but actually doing so wouldn't be too hard.

    This is just a quickie I knocked up to test the idea. You could probably make it all objecty, and moosey if you preferred:

    package Object::Holder; use strict; use warnings; =head1 NAME Object::Holder - A module for working with parameters. =head1 SYNOPSIS =for example begin #!/usr/bin/perl -w use Object::Holder use strict; my $helper = Object::Holder->new( foo => "bar", bar => "baz" ); my @keys = $helper->param(); my $bar = $helper->param( "bar" ); =for example end =cut sub new { my ( $proto, %supplied ) = (@_); my $class = ref($proto) || $proto; my $self = {}; $self->{ "data" } = {}; # # Store the supplied key=>val pairs in our data section. # foreach my $key ( keys %supplied ) { $self->{ "data" }->{ lc $key } = $supplied{ $key }; } bless( $self, $class ); return $self; } sub param { my ( $self, $param ) = (@_); if ($param) { # return the value of the named param. return ( $self->{ "data" }->{ $param } ); } else { # return all the param names. return ( keys %{ $self->{ "data" } } ); } } 1; package main; my $o = Object::Holder->new( foo => "foo", steve => "kemp " ); # # Get all # my @params = $o->param(); foreach my $param (@params) { # # Get single # print "READ: $param -> " . $o->param($param) . "\n"; }

      Interesting. That appears to be pretty good for a quickie. That does look like it covers a lot of what I usually do with the param() method.

      However (and this goes back to wanting an RFC type thing), the param method does more. I believe that you are able to set values (not too bad to implement) and I believe that you are supposed to be able to have multiple values (array refs) per parameter. Again, I don't believe that those would be too difficult to implement off of what you presented here, but I wonder what other features I am missing.

      The Data::FormValidator (and I keep going back to that because it is the package that made me think about this) uses an object with a param method, but I don't know what features of the param method are used. Probably the most basic like you described above, but a complete param() method would be desirable.

      Thank you (both) very much for your time. If you have any more ideas, I would appreciate them.

        Allow me to throw my hat into the ring. I've tested this with Data::FormValidator and HTML::Template and it seems to work fine.

        package Object::WithParams; use warnings; use strict; use Carp qw/ croak /; =pod =head1 NAME Object::WithParams - An Object With Params =head1 VERSION Version 0.1 =cut our $VERSION = '0.1'; =head1 SYNOPSIS use Object::WithParams; my $thingy = Object::WithParams->new(); # set a param $thingy->param(veggie => 'tomato'); # get a param my $veggie = $thingy->param('veggie'); # $veggie eq 'tomato' # get all params my @params = $thingy->param(); # @params == ('veggie') # clone a Object::WithParams my $doodad = $thingy->clone; # $doodad->param('veggie') == 'tomato +' # delete a param $thingy->delete('veggie'); # delete all params $thingy->clear(); =head1 DESCRIPTION Use this module to create objects that do nothing except contain param +eters defined by you which you can get and set as you wish. Many modules su +ch as L<Data::FormValidator> have methods that accept an object with a param +() method and this object should be compatible with all of them. This module really ought to be a role but there is no standardized way + to do that in Perl 5. (Not everyone uses L<Moose>.) =head1 METHODS =head2 new Creates a new, empty L<Object::WithParams>. =cut sub new { my ($class) = @_; my $self = {}; return bless $self, $class; } =head2 clear Deletes all the extent parameters. Does not return anything. $thingy->clear(); =cut sub clear { my ($self) = @_; foreach my $param ( keys %{$self} ) { delete $self->{$param}; } return; } =head2 clone Returns a new L<Object::WithParams> with the same set of parameters as + the old one. my $doodad = $thingy->clone(); =cut sub clone { my ($self) = @_; my $clone = Object::WithParams->new(); foreach my $param ( $self->param() ) { $clone->param( $param => $self->param($param) ); } return $clone; } =head2 delete Delete the named parameter. $thingy->delete('veggie'); =cut sub delete { ## no critic 'Subroutines::ProhibitBuiltinHomonyms' my ( $self, $param ) = @_; if ( defined $param && exists $self->{$param} ) { delete $self->{$param}; } return; } =head2 param The C<param> method can be called in three ways. =over 4 =item with no arguments. Returns a list of the parameters contained in the object. my @params = $thingy->param(); =item with a single scalar argument. The value of the parameter with the name of the argument will be retur +ned. my $color = $thingy->param('color'); =item with named arguments A parameter is created for one or more sets of keys and values. $thingy->param(filename => 'logo.jpg', height => 50, width => 100); You could also use a hashref. my $arg_ref = { filename => 'logo.jpg', height => 50, width => 100 }; $thingy->param($arg_ref); The value of a parameter need not be a scalar, it could be any any sor +t of reference even a coderef. $thingy->param(number => &pick_a_random_number); Does not return anything. =back =cut sub param { my ( $self, @args ) = @_; my $num_args = scalar @args; if ($num_args) { if ( ref $args[0] eq 'HASH' ) { # a hashref %{$self} = ( %{$self}, %{ $args[0] } ); } elsif ( $num_args % 2 == 0 ) { # a hash %{$self} = ( %{$self}, @args ); } elsif ( $num_args == 1 ) { # a scalar return $self->{ $args[0] }; } else { croak('Odd number of arguments passed to param().'); } } else { return keys %{$self}; } return; } 1;

        What do you think? I can finish writing the tests and put it up on on CPAN if it is of interest.


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