use warnings;
use Carp 'confess';
-use Scalar::Util 'blessed', 'reftype';
+use Scalar::Util 'blessed', 'reftype', 'weaken';
-our $VERSION = '0.01';
+our $VERSION = '0.03';
sub meta {
require Class::MOP::Class;
(defined $name && $name)
|| confess "You must provide a name for the attribute";
- (!exists $options{reader} && !exists $options{writer})
- || confess "You cannot declare an accessor and reader and/or writer functions"
- if exists $options{accessor};
+ $options{init_arg} = $name
+ if not exists $options{init_arg};
bless {
name => $name,
writer => $options{writer},
predicate => $options{predicate},
init_arg => $options{init_arg},
- default => $options{default}
+ default => $options{default},
+ # keep a weakened link to the
+ # class we are associated with
+ associated_class => undef,
} => $class;
}
+# NOTE:
+# this is a primative (and kludgy) clone operation
+# for now, it will be repleace in the Class::MOP
+# bootstrap with a proper one, however we know
+# that this one will work fine for now.
+sub clone {
+ my $self = shift;
+ my %options = @_;
+ (blessed($self))
+ || confess "Can only clone an instance";
+ return bless { %{$self}, %options } => blessed($self);
+}
+
+# NOTE:
+# the next bunch of methods will get bootstrapped
+# away in the Class::MOP bootstrapping section
+
sub name { $_[0]->{name} }
+sub associated_class { $_[0]->{associated_class} }
+
sub has_accessor { defined($_[0]->{accessor}) ? 1 : 0 }
sub has_reader { defined($_[0]->{reader}) ? 1 : 0 }
sub has_writer { defined($_[0]->{writer}) ? 1 : 0 }
sub predicate { $_[0]->{predicate} }
sub init_arg { $_[0]->{init_arg} }
+# end bootstrapped away method section.
+# (all methods below here are kept intact)
+
sub default {
my $self = shift;
if (reftype($self->{default}) && reftype($self->{default}) eq 'CODE') {
$self->{default};
}
-{
- # this is just a utility routine to
- # handle the details of accessors
- my $_inspect_accessor = sub {
- my ($attr_name, $type, $accessor) = @_;
-
- my %ACCESSOR_TEMPLATES = (
- 'accessor' => qq{sub {
- \$_[0]->{'$attr_name'} = \$_[1] if scalar(\@_) == 2;
- \$_[0]->{'$attr_name'};
- }},
- 'reader' => qq{sub {
- \$_[0]->{'$attr_name'};
- }},
- 'writer' => qq{sub {
- \$_[0]->{'$attr_name'} = \$_[1];
- return;
- }},
- 'predicate' => qq{sub {
- return defined \$_[0]->{'$attr_name'} ? 1 : 0;
- }}
- );
-
- if (reftype($accessor) && reftype($accessor) eq 'HASH') {
- my ($name, $method) = each %{$accessor};
- return ($name, Class::MOP::Attribute::Accessor->wrap($method));
- }
- else {
- my $method = eval $ACCESSOR_TEMPLATES{$type};
- confess "Could not create the $type for $attr_name CODE(\n" . $ACCESSOR_TEMPLATES{$type} . "\n) : $@" if $@;
- return ($accessor => Class::MOP::Attribute::Accessor->wrap($method));
- }
- };
+# class association
- sub install_accessors {
- my ($self, $class) = @_;
- (blessed($class) && $class->isa('Class::MOP::Class'))
- || confess "You must pass a Class::MOP::Class instance (or a subclass)";
- $class->add_method(
- $_inspect_accessor->($self->name, 'accessor' => $self->accessor())
- ) if $self->has_accessor();
-
- $class->add_method(
- $_inspect_accessor->($self->name, 'reader' => $self->reader())
- ) if $self->has_reader();
-
- $class->add_method(
- $_inspect_accessor->($self->name, 'writer' => $self->writer())
- ) if $self->has_writer();
-
- $class->add_method(
- $_inspect_accessor->($self->name, 'predicate' => $self->predicate())
- ) if $self->has_predicate();
- return;
+sub attach_to_class {
+ my ($self, $class) = @_;
+ (blessed($class) && $class->isa('Class::MOP::Class'))
+ || confess "You must pass a Class::MOP::Class instance (or a subclass)";
+ weaken($self->{associated_class} = $class);
+}
+
+sub detach_from_class {
+ my $self = shift;
+ $self->{associated_class} = undef;
+}
+
+## Method generation helpers
+
+sub generate_accessor_method {
+ my ($self, $attr_name) = @_;
+ eval qq{sub {
+ \$_[0]->{'$attr_name'} = \$_[1] if scalar(\@_) == 2;
+ \$_[0]->{'$attr_name'};
+ }};
+}
+
+sub generate_reader_method {
+ my ($self, $attr_name) = @_;
+ eval qq{sub {
+ \$_[0]->{'$attr_name'};
+ }};
+}
+
+sub generate_writer_method {
+ my ($self, $attr_name) = @_;
+ eval qq{sub {
+ \$_[0]->{'$attr_name'} = \$_[1];
+ }};
+}
+
+sub generate_predicate_method {
+ my ($self, $attr_name) = @_;
+ eval qq{sub {
+ defined \$_[0]->{'$attr_name'} ? 1 : 0;
+ }};
+}
+
+sub process_accessors {
+ my ($self, $type, $accessor) = @_;
+ if (reftype($accessor) && reftype($accessor) eq 'HASH') {
+ my ($name, $method) = each %{$accessor};
+ return ($name, Class::MOP::Attribute::Accessor->wrap($method));
}
+ else {
+ my $generator = $self->can('generate_' . $type . '_method');
+ ($generator)
+ || confess "There is no method generator for the type='$type'";
+ if (my $method = $self->$generator($self->name)) {
+ return ($accessor => Class::MOP::Attribute::Accessor->wrap($method));
+ }
+ confess "Could not create the '$type' method for " . $self->name . " because : $@";
+ }
+}
+
+sub install_accessors {
+ my $self = shift;
+ my $class = $self->associated_class;
+ $class->add_method(
+ $self->process_accessors('accessor' => $self->accessor())
+ ) if $self->has_accessor();
+
+ $class->add_method(
+ $self->process_accessors('reader' => $self->reader())
+ ) if $self->has_reader();
+
+ $class->add_method(
+ $self->process_accessors('writer' => $self->writer())
+ ) if $self->has_writer();
+
+ $class->add_method(
+ $self->process_accessors('predicate' => $self->predicate())
+ ) if $self->has_predicate();
+ return;
}
{
};
sub remove_accessors {
- my ($self, $class) = @_;
- (blessed($class) && $class->isa('Class::MOP::Class'))
- || confess "You must pass a Class::MOP::Class instance (or a subclass)";
- $_remove_accessor->($self->accessor(), $class) if $self->has_accessor();
- $_remove_accessor->($self->reader(), $class) if $self->has_reader();
- $_remove_accessor->($self->writer(), $class) if $self->has_writer();
- $_remove_accessor->($self->predicate(), $class) if $self->has_predicate();
+ my $self = shift;
+ $_remove_accessor->($self->accessor(), $self->associated_class()) if $self->has_accessor();
+ $_remove_accessor->($self->reader(), $self->associated_class()) if $self->has_reader();
+ $_remove_accessor->($self->writer(), $self->associated_class()) if $self->has_writer();
+ $_remove_accessor->($self->predicate(), $self->associated_class()) if $self->has_predicate();
return;
}
=head1 SYNOPSIS
Class::MOP::Attribute->new('$foo' => (
- accessor => 'foo', # dual purpose get/set accessor
- init_arg => '-foo', # class->new will look for a -foo key
- default => 'BAR IS BAZ!' # if no -foo key is provided, use this
+ accessor => 'foo', # dual purpose get/set accessor
+ predicate => 'has_foo' # predicate check for defined-ness
+ init_arg => '-foo', # class->new will look for a -foo key
+ default => 'BAR IS BAZ!' # if no -foo key is provided, use this
));
Class::MOP::Attribute->new('$.bar' => (
- reader => 'bar', # getter
- writer => 'set_bar', # setter
- init_arg => '-bar', # class->new will look for a -bar key
+ reader => 'bar', # getter
+ writer => 'set_bar', # setter
+ predicate => 'has_bar' # predicate check for defined-ness
+ init_arg => ':bar', # class->new will look for a :bar key
# no default value means it is undef
));
=head1 DESCRIPTION
-The Attribute Protocol is almost entirely an invention of this module. This is
-because Perl 5 does not have consistent notion of what is an attribute
-of a class. There are so many ways in which this is done, and very few
-(if any) are discoverable by this module.
+The Attribute Protocol is almost entirely an invention of this module,
+and is completely optional to this MOP. This is because Perl 5 does not
+have consistent notion of what is an attribute of a class. There are
+so many ways in which this is done, and very few (if any) are
+easily discoverable by this module.
So, all that said, this module attempts to inject some order into this
-chaos, by introducing a more consistent approach.
+chaos, by introducing a consistent API which can be used to create
+object attributes.
=head1 METHODS
=over 4
-=item B<new ($name, %options)>
+=item B<new ($name, ?%options)>
+
+An attribute must (at the very least), have a C<$name>. All other
+C<%options> are contained added as key-value pairs. Acceptable keys
+are as follows:
+
+=item B<clone (%options)>
+
+=over 4
+
+=item I<init_arg>
+
+This should be a string value representing the expected key in
+an initialization hash. For instance, if we have an I<init_arg>
+value of C<-foo>, then the following code will Just Work.
+
+ MyClass->meta->construct_instance(-foo => "Hello There");
+
+In an init_arg is not assigned, it will automatically use the
+value of C<$name>.
+
+=item I<default>
+
+The value of this key is the default value which
+C<Class::MOP::Class::construct_instance> will initialize the
+attribute to.
+
+B<NOTE:>
+If the value is a simple scalar (string or number), then it can
+be just passed as is. However, if you wish to initialize it with
+a HASH or ARRAY ref, then you need to wrap that inside a CODE
+reference, like so:
+
+ Class::MOP::Attribute->new('@foo' => (
+ default => sub { [] },
+ ));
+
+ # or ...
+
+ Class::MOP::Attribute->new('%foo' => (
+ default => sub { {} },
+ ));
+
+If you wish to initialize an attribute with a CODE reference
+itself, then you need to wrap that in a subroutine as well, like
+so:
+
+ Class::MOP::Attribute->new('&foo' => (
+ default => sub { sub { print "Hello World" } },
+ ));
+
+And lastly, if the value of your attribute is dependent upon
+some other aspect of the instance structure, then you can take
+advantage of the fact that when the I<default> value is a CODE
+reference, it is passed the raw (unblessed) instance structure
+as it's only argument. So you can do things like this:
+
+ Class::MOP::Attribute->new('$object_identity' => (
+ default => sub { Scalar::Util::refaddr($_[0]) },
+ ));
+
+This last feature is fairly limited as there is no gurantee of
+the order of attribute initializations, so you cannot perform
+any kind of dependent initializations. However, if this is
+something you need, you could subclass B<Class::MOP::Class> and
+this class to acheive it. However, this is currently left as
+an exercise to the reader :).
+
+=back
+
+The I<accessor>, I<reader>, I<writer> and I<predicate> keys can
+contain either; the name of the method and an appropriate default
+one will be generated for you, B<or> a HASH ref containing exactly one
+key (which will be used as the name of the method) and one value,
+which should contain a CODE reference which will be installed as
+the method itself.
=over 4
=item I<accessor>
+The I<accessor> is a standard perl-style read/write accessor. It will
+return the value of the attribute, and if a value is passed as an argument,
+it will assign that value to the attribute.
+
+B<NOTE:>
+This method will properly handle the following code, by assigning an
+C<undef> value to the attribute.
+
+ $object->set_something(undef);
+
=item I<reader>
+This is a basic read-only accessor, it will just return the value of
+the attribute.
+
=item I<writer>
-=item I<predicate>
+This is a basic write accessor, it accepts a single argument, and
+assigns that value to the attribute. This method does not intentially
+return a value, however perl will return the result of the last
+expression in the subroutine, which returns in this returning the
+same value that it was passed.
-=item I<init_arg>
+B<NOTE:>
+This method will properly handle the following code, by assigning an
+C<undef> value to the attribute.
-=item I<default>
+ $object->set_something();
+
+=item I<predicate>
+
+This is a basic test to see if the value of the attribute is not
+C<undef>. It will return true (C<1>) if the attribute's value is
+defined, and false (C<0>) otherwise.
=back
=head2 Informational
+These are all basic read-only value accessors for the values
+passed into C<new>. I think they are pretty much self-explanitory.
+
=over 4
=item B<name>
=item B<init_arg>
-=item B<default>
+=item B<default (?$instance)>
+
+As noted in the documentation for C<new> above, if the I<default>
+value is a CODE reference, this accessor will pass a single additional
+argument C<$instance> into it and return the value.
=back
=head2 Informational predicates
+These are all basic predicate methods for the values passed into C<new>.
+
=over 4
=item B<has_accessor>
-Returns true if this attribute uses a get/set accessor, and false
-otherwise
-
=item B<has_reader>
-Returns true if this attribute has a reader, and false otherwise
-
=item B<has_writer>
-Returns true if this attribute has a writer, and false otherwise
-
=item B<has_predicate>
-Returns true if this attribute has a predicate, and false otherwise
-
=item B<has_init_arg>
-Returns true if this attribute has a class intialization argument, and
-false otherwise
-
=item B<has_default>
-Returns true if this attribute has a default value, and false
-otherwise.
+=back
+
+=head2 Class association
+
+=over 4
+
+=item B<associated_class>
+
+=item B<attach_to_class ($class)>
+
+=item B<detach_from_class>
=back
=over 4
-=item B<install_accessors ($class)>
+=item B<install_accessors>
This allows the attribute to generate and install code for it's own
-accessor methods. This is called by C<Class::MOP::Class::add_attribute>.
+I<accessor/reader/writer/predicate> methods. This is called by
+C<Class::MOP::Class::add_attribute>.
+
+This method will call C<process_accessors> for each of the possible
+method types (accessor, reader, writer & predicate).
-=item B<remove_accessors ($class)>
+=item B<process_accessors ($type, $value)>
+
+This takes a C<$type> (accessor, reader, writer or predicate), and
+a C<$value> (the value passed into the constructor for each of the
+different types). It will then either generate the method itself
+(using the C<generate_*_method> methods listed below) or it will
+use the custom method passed through the constructor.
+
+=over 4
+
+=item B<generate_accessor_method ($attr_name)>
+
+=item B<generate_predicate_method ($attr_name)>
+
+=item B<generate_reader_method ($attr_name)>
+
+=item B<generate_writer_method ($attr_name)>
+
+=back
+
+=item B<remove_accessors>
This allows the attribute to remove the method for it's own
-accessor. This is called by C<Class::MOP::Class::remove_attribute>.
+I<accessor/reader/writer/predicate>. This is called by
+C<Class::MOP::Class::remove_attribute>.
=back
=item B<meta>
+This will return a B<Class::MOP::Class> instance which is related
+to this class.
+
+It should also be noted that B<Class::MOP> will actually bootstrap
+this module by installing a number of attribute meta-objects into
+it's metaclass. This will allow this class to reap all the benifits
+of the MOP when subclassing it.
+
=back
=head1 AUTHOR
-Stevan Little E<gt>stevan@iinteractive.comE<lt>
+Stevan Little E<lt>stevan@iinteractive.comE<gt>
=head1 COPYRIGHT AND LICENSE
projects / gitmo/Class-MOP.git / blobdiff