Junio C Hamano wrote:
That's how you would write class methods, isn't it? IOW, your callers
can say:
my $self = new Git();
$self->method(qw(a b c));
Git::method(qw(a b c))
and you can start your method like this:
sub method {
my ($self, @args) = _maybe_self(@_)
...
}
and use @args the same way for either form of the call in the
implementation.
I see, a magic way to offer both an OO and procedural api. Well, partial
procedural api, since not all of the methods can work without the $self.
Two obvious pitfalls are:
- You cannot use $self if you set up your parameters with _maybe_self;
- The second form of the call would call directly into Git::method, never
your subclasses implementation, even if you write:
use Git;
package CJGit;
our @ISA = qw(Git);
sub method {
...
}
(This is no problem iff people are calling procedures in object notation
if they actually have got an object at hands. I.e. if you've got some
code which does:
my $repo= Git->repository(...);
$repo->foo;
then all is fine, and I would think it would be weird if people called
Git::foo($repo, ... ) in such a case. Well for my purposes it's not a
problem anyway, since if a user wants to use the extensions, he needs to
actually do this:
my $repo= CJGit->repository(...);
and then it should be clear that one shouldn't call Git:: directly. The
problem will only be in cases where an extended object is being fed to
existing code which calls Git:: with objects in the hope that virtual
method calls are going to the extended class; well, let's fix those bad
call sites when they are being discovered... Maybe this warrants a
warning somewhere.)
sub _maybe_self {
- # This breaks inheritance. Oh well.
- ref $_[0] eq 'Git' ? @_ : (undef, @_);
+ UNIVERSAL::isa($_[0], 'Git') ? @_ : (undef, @_);
}
# Check if the command id is something reasonable.
The patch looks Ok, as long as you have a working UNIVERSAL::isa() in your
version of Perl. My reading of perl561delta,pod says that Perl 5.6.1 and
later should have a working implementation.
From http://perldoc.perl.org/perl561delta.html:
UNIVERSAL::isa()
A bug in the caching mechanism used by UNIVERSAL::isa() that affected
base.pm has been fixed. The bug has existed since the 5.005 releases,
but wasn't tickled by base.pm in those releases.
This looks like only a bug in some (corner?) cases; I've verified that
I've been using the isa() method *or* function since perl 5.005_03, and
haven't had issues with it. I can't easily verify though when I switched
from
#if (Scalar::Util::blessed($value) and $value->isa("Eile::Html")) {
to
if (UNIVERSAL::isa($value,"Eile::Html")) {
(because it was simpler to write, once I discovered that I could just
call the function directly instead of relying on method dispatch) but
that might not have made a difference.
Christian.
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