How do I make object methods callable as non-OO functions?

For example, say I have a class 'Foo' that is used thusly:

  use Foo;
  my $f = Foo->new(%args);
  my $g = $f->frobnicate;
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but for some Very Good Reason, we want to be able to call it in a more procedural fashion:

  use Foo 'frobnicate';
  my $g = frobnicate($args);
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Is there a good way of doing this? Is there a good reason not to do this?

Originally posted as a Categorized Question.

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Re: How do I make object methods callable as non-OO functions?⭐ by jhourcle (Prior) on Mar 25, 2005 at 03:51 UTC
I use the following at the beginning of the sub, so I can still use $self, and someone can override the functions in a derived class, if need be. (it won't work with your exact calling syntax though, as it's mostly for items that don't require values from the actual object). `sub function_name { # for a function call my $self = __PACKAGE__; # for a method call $self = shift if UNIVERSAL::isa( $_[0], __PACKAGE__ ); ... }` [download] You could also write do the shorter, more efficient, but potentially more confusing : `sub function_name { my $self = UNIVERSAL::isa( $_[0], __PACKAGE__ ) ? shift : __PACKAGE__; ... }` [download]	[reply] [d/l] [select]
Re: Answer: How do I make object methods callable as non-OO functions? by cazz (Pilgrim) on Mar 25, 2005 at 15:27 UTC
CGI.pm does something simliar, except with a generic sub. `sub self_or_default { return @_ if defined($_[0]) && (!ref($_[0])) &&($_[0] eq 'CGI'); unless (defined($_[0]) && (ref($_[0]) eq 'CGI' \|\| UNIVERSAL::isa($_[0],'CGI')) # slightl +y optimized for common case ) { $Q = $CGI::DefaultClass->new unless defined($Q); unshift(@_,$Q); } return wantarray ? @_ : $Q; }` [download] Then they use it like this: `sub url_param { my ($self,@p) = self_or_default(@_); my $name = shift(@p); return undef unless exists($ENV{QUERY_STRING}); ...` [download]	[reply] [d/l] [select]
Re: How do I make object methods callable as non-OO functions? by cosimo (Hermit) on Jun 30, 2004 at 12:09 UTC
Probably, what you want is something like: `package Foo; sub new { # A noop constructor bless {}, shift; } sub frobnicate { my($self, @args) = @_; unless($self eq 'Foo' \|\| (ref $self && $self->isa('Foo'))) { unshift @args, $self; undef $self; } # Now $self is available only if you have an OO call # List of @args is always the same return join(', ', @args). "\n"; }` [download] and use it in the following way: `my $f = Foo->new(); print $f->frobnicate('my','args'); # or print Foo::frobnicate('my','args'); # or even print Foo->frobnicate('my','args');` [download] Beware, though that doing something like `$self->isa('Foo')` breaks inheritance mechanisms and IMHO it is a Bad Thing (tm). As usual, perl "gives you enough rope to hang yourself", which is a Good Thing (tm) :-)	[reply] [d/l] [select]
Re: How do I make object methods callable as non-OO functions? by Anonymous Monk on Jun 25, 2004 at 21:58 UTC
`use Exporter; @ISA = ('Exporter'); @EXPORT = @EXPORT_OK = qw(frobnicate);` [download] frobnicate is then available both as an OO-subroutine and a procedural one...	[reply] [d/l]