our $VERSION = '0.01';
+# Self-introspection
+
+sub meta { $_[0]->initialize($_[0]) }
+
# Creation
{
sub initialize {
my ($class, $package_name) = @_;
(defined $package_name && $package_name)
- || confess "You must pass a package name";
- $METAS{$package_name} ||= bless \$package_name => blessed($class) || $class;
+ || confess "You must pass a package name";
+ return $METAS{$package_name} if exists $METAS{$package_name};
+ $METAS{$package_name} = $class->construct_class_instance($package_name);
+ }
+
+ # NOTE: (meta-circularity)
+ # this is a special form of &construct_instance
+ # (see below), which is used to construct class
+ # meta-object instances for any Class::MOP::*
+ # class. All other classes will use the more
+ # normal &construct_instance.
+ sub construct_class_instance {
+ my ($class, $package_name) = @_;
+ (defined $package_name && $package_name)
+ || confess "You must pass a package name";
+ $class = blessed($class) || $class;
+ if ($class =~ /^Class::MOP::/) {
+ bless {
+ '$:pkg' => $package_name,
+ '%:attrs' => {}
+ } => $class;
+ }
+ else {
+ bless $class->meta->construct_instance(':pkg' => $package_name) => $class
+ }
}
}
my $meta = $class->initialize($package_name);
$meta->superclasses(@{$options{superclasses}})
if exists $options{superclasses};
+ # NOTE:
+ # process attributes first, so that they can
+ # install accessors, but locally defined methods
+ # can then overwrite them. It is maybe a little odd, but
+ # I think this should be the order of things.
+ if (exists $options{attributes}) {
+ foreach my $attr (@{$options{attributes}}) {
+ $meta->add_attribute($attr);
+ }
+ }
if (exists $options{methods}) {
foreach my $method_name (keys %{$options{methods}}) {
$meta->add_method($method_name, $options{methods}->{$method_name});
}
- }
+ }
return $meta;
}
+# Instance Construction
+
+sub construct_instance {
+ my ($class, %params) = @_;
+ my $instance = {};
+ foreach my $attr (map { $_->{attribute} } $class->compute_all_applicable_attributes()) {
+ # if the attr has an init_arg, use that, otherwise,
+ # use the attributes name itself as the init_arg
+ my $init_arg = $attr->has_init_arg() ? $attr->init_arg() : $attr->name;
+ # try to fetch the init arg from the %params ...
+ my $val;
+ $val = $params{$init_arg} if exists $params{$init_arg};
+ # if nothing was in the %params, we can use the
+ # attribute's default value (if it has one)
+ $val ||= $attr->default($instance) if $attr->has_default();
+ # now add this to the instance structure
+ $instance->{$attr->name} = $val;
+ }
+ return $instance;
+}
+
# Informational
-sub name { ${$_[0]} }
+sub name { $_[0]->{'$:pkg'} }
sub version {
my $self = shift;
my ($self, $method_name, $method) = @_;
(defined $method_name && $method_name)
|| confess "You must define a method name";
+ # use reftype here to allow for blessed subs ...
(reftype($method) && reftype($method) eq 'CODE')
|| confess "Your code block must be a CODE reference";
my $full_method_name = ($self->name . '::' . $method_name);
no strict 'refs';
+ no warnings 'redefine';
*{$full_method_name} = subname $full_method_name => $method;
}
{
## private utility functions for has_method
- my $_find_subroutine_package_name = sub { eval { svref_2object($_[0])->GV->STASH->NAME } };
- my $_find_subroutine_name = sub { eval { svref_2object($_[0])->GV->NAME } };
+ my $_find_subroutine_package_name = sub { eval { svref_2object($_[0])->GV->STASH->NAME } || '' };
+ my $_find_subroutine_name = sub { eval { svref_2object($_[0])->GV->NAME } || '' };
sub has_method {
- my ($self, $method_name, $method) = @_;
+ my ($self, $method_name) = @_;
(defined $method_name && $method_name)
|| confess "You must define a method name";
}
sub get_method {
- my ($self, $method_name, $method) = @_;
+ my ($self, $method_name) = @_;
(defined $method_name && $method_name)
|| confess "You must define a method name";
no strict 'refs';
return \&{$self->name . '::' . $method_name}
if $self->has_method($method_name);
- return; # <--- make sure to return undef
+ return; # <- make sure to return undef
+}
+
+sub remove_method {
+ my ($self, $method_name) = @_;
+ (defined $method_name && $method_name)
+ || confess "You must define a method name";
+
+ my $removed_method = $self->get_method($method_name);
+
+ no strict 'refs';
+ delete ${$self->name . '::'}{$method_name}
+ if defined $removed_method;
+
+ return $removed_method;
+}
+
+sub get_method_list {
+ my $self = shift;
+ no strict 'refs';
+ grep { $self->has_method($_) } %{$self->name . '::'};
+}
+
+sub compute_all_applicable_methods {
+ my $self = shift;
+ my @methods;
+ # keep a record of what we have seen
+ # here, this will handle all the
+ # inheritence issues because we are
+ # using the &class_precedence_list
+ my (%seen_class, %seen_method);
+ foreach my $class ($self->class_precedence_list()) {
+ next if $seen_class{$class};
+ $seen_class{$class}++;
+ # fetch the meta-class ...
+ my $meta = $self->initialize($class);
+ foreach my $method_name ($meta->get_method_list()) {
+ next if exists $seen_method{$method_name};
+ $seen_method{$method_name}++;
+ push @methods => {
+ name => $method_name,
+ class => $class,
+ code => $meta->get_method($method_name)
+ };
+ }
+ }
+ return @methods;
+}
+
+sub find_all_methods_by_name {
+ my ($self, $method_name) = @_;
+ (defined $method_name && $method_name)
+ || confess "You must define a method name to find";
+ my @methods;
+ # keep a record of what we have seen
+ # here, this will handle all the
+ # inheritence issues because we are
+ # using the &class_precedence_list
+ my %seen_class;
+ foreach my $class ($self->class_precedence_list()) {
+ next if $seen_class{$class};
+ $seen_class{$class}++;
+ # fetch the meta-class ...
+ my $meta = $self->initialize($class);
+ push @methods => {
+ name => $method_name,
+ class => $class,
+ code => $meta->get_method($method_name)
+ } if $meta->has_method($method_name);
+ }
+ return @methods;
+
+}
+
+## Attributes
+
+sub add_attribute {
+ my ($self,$attribute) = @_;
+ (blessed($attribute) && $attribute->isa('Class::MOP::Attribute'))
+ || confess "Your attribute must be an instance of Class::MOP::Attribute (or a subclass)";
+ $attribute->install_accessors($self);
+ $self->{'%:attrs'}->{$attribute->name} = $attribute;
+}
+
+sub has_attribute {
+ my ($self, $attribute_name) = @_;
+ (defined $attribute_name && $attribute_name)
+ || confess "You must define an attribute name";
+ exists $self->{'%:attrs'}->{$attribute_name} ? 1 : 0;
+}
+
+sub get_attribute {
+ my ($self, $attribute_name) = @_;
+ (defined $attribute_name && $attribute_name)
+ || confess "You must define an attribute name";
+ return $self->{'%:attrs'}->{$attribute_name}
+ if $self->has_attribute($attribute_name);
+}
+
+sub remove_attribute {
+ my ($self, $attribute_name) = @_;
+ (defined $attribute_name && $attribute_name)
+ || confess "You must define an attribute name";
+ my $removed_attribute = $self->{'%:attrs'}->{$attribute_name};
+ delete $self->{'%:attrs'}->{$attribute_name}
+ if defined $removed_attribute;
+ $removed_attribute->remove_accessors($self);
+ return $removed_attribute;
+}
+
+sub get_attribute_list {
+ my $self = shift;
+ keys %{$self->{'%:attrs'}};
+}
+
+sub compute_all_applicable_attributes {
+ my $self = shift;
+ my @attrs;
+ # keep a record of what we have seen
+ # here, this will handle all the
+ # inheritence issues because we are
+ # using the &class_precedence_list
+ my (%seen_class, %seen_attr);
+ foreach my $class ($self->class_precedence_list()) {
+ next if $seen_class{$class};
+ $seen_class{$class}++;
+ # fetch the meta-class ...
+ my $meta = $self->initialize($class);
+ foreach my $attr_name ($meta->get_attribute_list()) {
+ next if exists $seen_attr{$attr_name};
+ $seen_attr{$attr_name}++;
+ push @attrs => {
+ name => $attr_name,
+ class => $class,
+ attribute => $meta->get_attribute($attr_name)
+ };
+ }
+ }
+ return @attrs;
}
1;
=head1 SYNOPSIS
+ # use this for introspection ...
+
+ package Foo;
+ sub meta { Class::MOP::Class->initialize(__PACKAGE__) }
+
+ # elsewhere in the code ...
+
+ # add a method to Foo ...
+ Foo->meta->add_method('bar' => sub { ... })
+
+ # get a list of all the classes searched
+ # the method dispatcher in the correct order
+ Foo->meta->class_precedence_list()
+
+ # remove a method from Foo
+ Foo->meta->remove_method('bar');
+
+ # or use this to actually create classes ...
+
+ Class::MOP::Class->create('Bar' => '0.01' => (
+ superclasses => [ 'Foo' ],
+ attributes => [
+ Class::MOP:::Attribute->new('$bar'),
+ Class::MOP:::Attribute->new('$baz'),
+ ],
+ methods => {
+ calculate_bar => sub { ... },
+ construct_baz => sub { ... }
+ }
+ ));
+
=head1 DESCRIPTION
+This is the largest and currently most complex part of the Perl 5
+meta-object protocol. It controls the introspection and
+manipulation of Perl 5 classes (and it can create them too). The
+best way to understand what this module can do, is to read the
+documentation for each of it's methods.
+
+=head1 METHODS
+
+=head2 Self Introspection
+
+=over 4
+
+=item B<meta>
+
+This will return a B<Class::MOP::Class> instance which is related
+to this class. Thereby allowing B<Class::MOP::Class> to actually
+introspect itself.
+
+As with B<Class::MOP::Attribute>, 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
+
+=head2 Class construction
+
+These methods handle creating Class objects, which can be used to
+both create new classes, and analyze pre-existing ones.
+
+This module will internally store references to all the instances
+you create with these methods, so that they do not need to be
+created any more than nessecary. Basically, they are singletons.
+
+=over 4
+
+=item B<create ($package_name, ?$package_version,
+ superclasses => ?@superclasses,
+ methods => ?%methods,
+ attributes => ?%attributes)>
+
+This returns the basic Class object, bringing the specified
+C<$package_name> into existence and adding any of the
+C<$package_version>, C<@superclasses>, C<%methods> and C<%attributes>
+to it.
+
+=item B<initialize ($package_name)>
+
+This initializes a Class object for a given a C<$package_name>.
+
+=back
+
+=head2 Instance construction
+
+=over 4
+
+=item B<construct_instance (%params)>
+
+This will construct and instance using a HASH ref as storage
+(currently only HASH references are supported). This will collect all
+the applicable attribute meta-objects and layout out the fields in the
+HASH ref, it will then initialize them using either use the
+corresponding key in C<%params> or any default value or initializer
+found in the attribute meta-object.
+
+=item B<construct_class_instance ($package_name)>
+
+This will construct an instance of B<Class::MOP::Class>, it is
+here so that we can actually "tie the knot" for B<Class::MOP::Class>
+to use C<construct_instance> once all the bootstrapping is done. This
+method is used internally by C<initialize> and should never be called
+from outside of that method really.
+
+=back
+
+=head2 Informational
+
+=over 4
+
+=item B<name>
+
+This is a read-only attribute which returns the package name that
+the Class is stored in.
+
+=item B<version>
+
+This is a read-only attribute which returns the C<$VERSION> of the
+package the Class is stored in.
+
+=back
+
+=head2 Inheritance Relationships
+
+=over 4
+
+=item B<superclasses (?@superclasses)>
+
+This is a read-write attribute which represents the superclass
+relationships of this Class. Basically, it can get and set the
+C<@ISA> for you.
+
+=item B<class_precedence_list>
+
+This computes the a list of the Class's ancestors in the same order
+in which method dispatch will be done.
+
+=back
+
+=head2 Methods
+
+=over 4
+
+=item B<add_method ($method_name, $method)>
+
+This will take a C<$method_name> and CODE reference to that
+C<$method> and install it into the Class.
+
+B<NOTE> : This does absolutely nothing special to C<$method>
+other than use B<Sub::Name> to make sure it is tagged with the
+correct name, and therefore show up correctly in stack traces and
+such.
+
+=item B<has_method ($method_name)>
+
+This just provides a simple way to check if the Class implements
+a specific C<$method_name>. It will I<not> however, attempt to check
+if the class inherits the method.
+
+This will correctly handle functions defined outside of the package
+that use a fully qualified name (C<sub Package::name { ... }>).
+
+This will correctly handle functions renamed with B<Sub::Name> and
+installed using the symbol tables. However, if you are naming the
+subroutine outside of the package scope, you must use the fully
+qualified name, including the package name, for C<has_method> to
+correctly identify it.
+
+This will attempt to correctly ignore functions imported from other
+packages using B<Exporter>. It breaks down if the function imported
+is an C<__ANON__> sub (such as with C<use constant>), which very well
+may be a valid method being applied to the class.
+
+In short, this method cannot always be trusted to determine if the
+C<$method_name> is actually a method. However, it will DWIM about
+90% of the time, so it's a small trade off IMO.
+
+=item B<get_method ($method_name)>
+
+This will return a CODE reference of the specified C<$method_name>,
+or return undef if that method does not exist.
+
+=item B<remove_method ($method_name)>
+
+This will attempt to remove a given C<$method_name> from the Class.
+It will return the CODE reference that it has removed, and will
+attempt to use B<Sub::Name> to clear the methods associated name.
+
+=item B<get_method_list>
+
+This will return a list of method names for all I<locally> defined
+methods. It does B<not> provide a list of all applicable methods,
+including any inherited ones. If you want a list of all applicable
+methods, use the C<compute_all_applicable_methods> method.
+
+=item B<compute_all_applicable_methods>
+
+This will return a list of all the methods names this Class will
+support, taking into account inheritance. The list will be a list of
+HASH references, each one containing the following information; method
+name, the name of the class in which the method lives and a CODE
+reference for the actual method.
+
+=item B<find_all_methods_by_name ($method_name)>
+
+This will traverse the inheritence hierarchy and locate all methods
+with a given C<$method_name>. Similar to
+C<compute_all_applicable_methods> it returns a list of HASH references
+with the following information; method name (which will always be the
+same as C<$method_name>), the name of the class in which the method
+lives and a CODE reference for the actual method.
+
+The list of methods produced is a distinct list, meaning there are no
+duplicates in it. This is especially useful for things like object
+initialization and destruction where you only want the method called
+once, and in the correct order.
+
+=back
+
+=head2 Attributes
+
+It should be noted that since there is no one consistent way to define
+the attributes of a class in Perl 5. These methods can only work with
+the information given, and can not easily discover information on
+their own.
+
+=over 4
+
+=item B<add_attribute ($attribute_name, $attribute_meta_object)>
+
+This stores a C<$attribute_meta_object> in the Class object and
+associates it with the C<$attribute_name>. Unlike methods, attributes
+within the MOP are stored as meta-information only. They will be used
+later to construct instances from (see C<construct_instance> above).
+More details about the attribute meta-objects can be found in the
+L<The Attribute protocol> section of this document.
+
+=item B<has_attribute ($attribute_name)>
+
+Checks to see if this Class has an attribute by the name of
+C<$attribute_name> and returns a boolean.
+
+=item B<get_attribute ($attribute_name)>
+
+Returns the attribute meta-object associated with C<$attribute_name>,
+if none is found, it will return undef.
+
+=item B<remove_attribute ($attribute_name)>
+
+This will remove the attribute meta-object stored at
+C<$attribute_name>, then return the removed attribute meta-object.
+
+B<NOTE:> Removing an attribute will only affect future instances of
+the class, it will not make any attempt to remove the attribute from
+any existing instances of the class.
+
+=item B<get_attribute_list>
+
+This returns a list of attribute names which are defined in the local
+class. If you want a list of all applicable attributes for a class,
+use the C<compute_all_applicable_attributes> method.
+
+=item B<compute_all_applicable_attributes>
+
+This will traverse the inheritance heirachy and return a list of HASH
+references for all the applicable attributes for this class. The HASH
+references will contain the following information; the attribute name,
+the class which the attribute is associated with and the actual
+attribute meta-object.
+
+=back
+
=head1 AUTHOR
Stevan Little E<gt>stevan@iinteractive.comE<lt>
projects / gitmo/Class-MOP.git / blobdiff