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=head1 TITLE
Replace $self in @_ with self() builtin (not $ME)
=head1 VERSION
Maintainer: Nathan Wiger <[EMAIL PROTECTED]>
Date: 24 Aug 2000
Version: 1
Mailing List: [EMAIL PROTECTED]
Number: 152
Status: Developing
=head1 ABSTRACT
Currently, the current object context is passed into a sub as the first
element of @_, leading to the familiar construct:
my $self = shift;
However, this is a big PITA. In particular, if you support lots of
different calling forms (like CGI.pm), you have to check whether $_[0]
is a ref, etc, etc, etc.
Much discussion has begun about the proposed $ME variable, which could
automatically contain this information. However, getting its scoping and
value right is a mess, and will result in a horrendous $AUTOLOAD
disaster that should not be repeated.
This RFC, therefore, proposes a new builtin called C<self()> which will
return the correct package information. This has the added advantage
that it is consistent with C<ref()>, C<want()>, and other context
functions.
=head1 DESCRIPTION
The new function C<self()> would be called in the following way:
sub do_stuff {
my $self = self;
$self->{STATE}->{something} = @_;
}
sub error {
carp @_ if self->config('VerboseErrors');
}
The return value of C<self()> would similar to the current value in
$_[0], with increased flexibility. In particular, it can be called
anywhere and everywhere, not just within a sub.
Depending on the context it's called in, the return value of C<self()>
will be:
1. A reference to the object, within an object
2. The name of the package, within a package
3. A reference to the sub itself, within a non-method
These different return values give us the ability to call C<self()>
anywhere within Perl 6 code:
package MyPackage;
# ... many other functions ...
sub do_stuff {
print "Hello, @_" if self->config('Yep');
}
self->do_stuff; # MyPackage->do_stuff
package main;
my $mp = new MyPackage;
$mp->config('Yep') = 1;
$mp->do_stuff('Nate'); # prints "Hello, Nate"
In addition, having a routine called C<self()> has the major advantage
that it hides the internal magic and scoping from the user. Just like
using C<want()> instead of a special variable called C<$WANT>, C<self()>
makes using and comprehending contexts easy ("just call 'self'").
Finally, it may be possible for self() to take an additional argument.
For example:
# Only return $self if are in the context of the class
# that is named 'DefaultClass' (see CGI.pm for an ex.)
if (my $self = self('DefaultClass')) {
$self->do_stuff;
} else {
# do something else
}
This is not required by the RFC, but seems like a useful extension.
=head1 IMPLEMENTATION
Replace the ref usually included in $_[0] with C<self()>. Stop passing
$self in @_.
=head1 MIGRATION
p52p6 would have to catch
my $self = shift;
and all other similar constructs and change them to
my $self = self;
or the equivalent.
=head1 REFERENCES
Mail archives on the $ME discussion:
http://www.mail-archive.com/perl6-language-objects%40perl.org/msg00023.html
http://www.mail-archive.com/perl6-language-objects%40perl.org/msg00025.html
http://www.mail-archive.com/perl6-language-objects%40perl.org/msg00026.html
RFC 21: Replace C<wantarray> with a generic C<want> function
