#!/usr/bin/env perl
package Mouse::Meta::Attribute;
use strict;
use warnings;
use Carp 'confess';
use Scalar::Util 'blessed';
sub new {
my $class = shift;
my %args = @_;
my $name = $args{name};
$args{init_arg} = $name
unless exists $args{init_arg};
$args{is} ||= '';
if ($args{lazy_build}) {
confess("You can not use lazy_build and default for the same attribute $name")
if exists $args{default};
$args{lazy} = 1;
$args{required} = 1;
$args{builder} ||= "_build_${name}";
if ($name =~ /^_/) {
$args{clearer} ||= "_clear${name}";
$args{predicate} ||= "_has${name}";
}
else {
$args{clearer} ||= "clear_${name}";
$args{predicate} ||= "has_${name}";
}
}
bless \%args, $class;
}
sub name { $_[0]->{name} }
sub class { $_[0]->{class} }
sub _is_metadata { $_[0]->{is} }
sub is_required { $_[0]->{required} }
sub default { $_[0]->{default} }
sub is_lazy { $_[0]->{lazy} }
sub is_lazy_build { $_[0]->{lazy_build} }
sub predicate { $_[0]->{predicate} }
sub clearer { $_[0]->{clearer} }
sub handles { $_[0]->{handles} }
sub is_weak_ref { $_[0]->{weak_ref} }
sub init_arg { $_[0]->{init_arg} }
sub type_constraint { $_[0]->{type_constraint} }
sub trigger { $_[0]->{trigger} }
sub builder { $_[0]->{builder} }
sub should_auto_deref { $_[0]->{auto_deref} }
sub has_default { exists $_[0]->{default} }
sub has_predicate { exists $_[0]->{predicate} }
sub has_clearer { exists $_[0]->{clearer} }
sub has_handles { exists $_[0]->{handles} }
sub has_type_constraint { exists $_[0]->{type_constraint} }
sub has_trigger { exists $_[0]->{trigger} }
sub has_builder { exists $_[0]->{builder} }
sub _create_args {
$_[0]->{_create_args} = $_[1] if @_ > 1;
$_[0]->{_create_args}
}
sub generate_accessor {
my $attribute = shift;
my $name = $attribute->name;
my $key = $name;
my $default = $attribute->default;
my $trigger = $attribute->trigger;
my $type = $attribute->type_constraint;
my $constraint = $attribute->find_type_constraint;
my $builder = $attribute->builder;
my $accessor = 'sub {
my $self = shift;';
if ($attribute->_is_metadata eq 'rw') {
$accessor .= 'if (@_) {
local $_ = $_[0];';
if ($constraint) {
$accessor .= 'do {
my $display = defined($_) ? overload::StrVal($_) : "undef";
Carp::confess("Attribute ($name) does not pass the type constraint because: Validation failed for \'$type\' failed with value $display") unless $constraint->();
};'
}
$accessor .= '$self->{$key} = $_;';
if ($attribute->is_weak_ref) {
$accessor .= 'Scalar::Util::weaken($self->{$key}) if ref($self->{$key});';
}
if ($trigger) {
$accessor .= '$trigger->($self, $_, $attribute);';
}
$accessor .= '}';
}
else {
$accessor .= 'confess "Cannot assign a value to a read-only accessor" if @_;';
}
if ($attribute->is_lazy) {
$accessor .= '$self->{$key} = ';
$accessor .= $attribute->has_builder
? '$self->$builder'
: ref($default) eq 'CODE'
? '$default->($self)'
: '$default';
$accessor .= ' if !exists($self->{$key});';
}
if ($attribute->should_auto_deref) {
if ($attribute->type_constraint eq 'ArrayRef') {
$accessor .= 'if (wantarray) {
return @{ $self->{$key} || [] };
}';
}
else {
$accessor .= 'if (wantarray) {
return %{ $self->{$key} || {} };
}';
}
}
$accessor .= 'return $self->{$key};
}';
return eval $accessor;
}
sub generate_predicate {
my $attribute = shift;
my $key = $attribute->name;
my $predicate = 'sub { exists($_[0]->{$key}) }';
return eval $predicate;
}
sub generate_clearer {
my $attribute = shift;
my $key = $attribute->name;
my $predicate = 'sub { delete($_[0]->{$key}) }';
return eval $predicate;
}
sub generate_handles {
my $attribute = shift;
my $reader = $attribute->name;
my %handles = $attribute->_canonicalize_handles($attribute->handles);
my %method_map;
for my $local_method (keys %handles) {
my $remote_method = $handles{$local_method};
my $method = 'sub {
my $self = shift;
$self->$reader->$remote_method(@_)
}';
$method_map{$local_method} = eval $method;
}
return \%method_map;
}
sub create {
my ($self, $class, $name, %args) = @_;
$args{name} = $name;
$args{class} = $class;
$self->validate_args($name, %args);
$args{type_constraint} = delete $args{isa}
if exists $args{isa};
my $attribute = $self->new(%args);
$attribute->_create_args(\%args);
my $meta = $class->meta;
$meta->add_attribute($attribute);
# install an accessor
if ($attribute->_is_metadata eq 'rw' || $attribute->_is_metadata eq 'ro') {
my $accessor = $attribute->generate_accessor;
no strict 'refs';
*{ $class . '::' . $name } = $accessor;
}
for my $method (qw/predicate clearer/) {
my $predicate = "has_$method";
if ($attribute->$predicate) {
my $generator = "generate_$method";
my $coderef = $attribute->$generator;
no strict 'refs';
*{ $class . '::' . $attribute->$method } = $coderef;
}
}
if ($attribute->has_handles) {
my $method_map = $attribute->generate_handles;
for my $method_name (keys %$method_map) {
no strict 'refs';
*{ $class . '::' . $method_name } = $method_map->{$method_name};
}
}
return $attribute;
}
sub validate_args {
my $self = shift;
my $name = shift;
my %args = @_;
confess "You cannot have lazy attribute ($name) without specifying a default value for it"
if $args{lazy} && !exists($args{default}) && !exists($args{builder});
confess "References are not allowed as default values, you must wrap the default of '$name' in a CODE reference (ex: sub { [] } and not [])"
if ref($args{default})
&& ref($args{default}) ne 'CODE';
confess "You cannot auto-dereference without specifying a type constraint on attribute $name"
if $args{auto_deref} && !exists($args{isa});
confess "You cannot auto-dereference anything other than a ArrayRef or HashRef on attribute $name"
if $args{auto_deref}
&& $args{isa} ne 'ArrayRef'
&& $args{isa} ne 'HashRef';
return 1;
}
sub find_type_constraint {
my $self = shift;
my $type = $self->type_constraint;
return unless $type;
my $checker = Mouse::TypeRegistry->optimized_constraints->{$type};
return $checker if $checker;
return sub { blessed($_) && blessed($_) eq $type };
}
sub verify_type_constraint {
my $self = shift;
local $_ = shift;
my $type = $self->type_constraint
or return 1;
my $constraint = $self->find_type_constraint;
return 1 if $constraint->($_);
my $name = $self->name;
my $display = defined($_) ? overload::StrVal($_) : 'undef';
Carp::confess("Attribute ($name) does not pass the type constraint because: Validation failed for \'$type\' failed with value $display");
}
sub _canonicalize_handles {
my $self = shift;
my $handles = shift;
if (ref($handles) eq 'HASH') {
return %$handles;
}
elsif (ref($handles) eq 'ARRAY') {
return map { $_ => $_ } @$handles;
}
else {
confess "Unable to canonicalize the 'handles' option with $handles";
}
}
sub clone_parent {
my $self = shift;
my $class = shift;
my $name = shift;
my %args = ($self->get_parent_args($class, $name), @_);
$self->create($class, $name, %args);
}
sub get_parent_args {
my $self = shift;
my $class = shift;
my $name = shift;
for my $super ($class->meta->linearized_isa) {
my $super_attr = $super->can("meta") && $super->meta->get_attribute($name)
or next;
return %{ $super_attr->_create_args };
}
confess "Could not find an attribute by the name of '$name' to inherit from";
}
1;
__END__
=head1 NAME
Mouse::Meta::Attribute - attribute metaclass
=head1 METHODS
=head2 new %args -> Mouse::Meta::Attribute
Instantiates a new Mouse::Meta::Attribute. Does nothing else.
=head2 create OwnerClass, AttributeName, %args -> Mouse::Meta::Attribute
Creates a new attribute in OwnerClass. Accessors and helper methods are
installed. Some error checking is done.
=head2 name -> AttributeName
=head2 class -> OwnerClass
=head2 is_required -> Bool
=head2 default -> Item
=head2 has_default -> Bool
=head2 is_lazy -> Bool
=head2 predicate -> MethodName | Undef
=head2 has_predicate -> Bool
=head2 clearer -> MethodName | Undef
=head2 has_clearer -> Bool
=head2 handles -> { LocalName => RemoteName }
=head2 has_handles -> Bool
=head2 is_weak_ref -> Bool
=head2 init_arg -> Str
=head2 type_constraint -> Str
=head2 has_type_constraint -> Bool
=head2 trigger => CODE | Undef
=head2 has_trigger -> Bool
=head2 builder => MethodName | Undef
=head2 has_builder -> Bool
=head2 should_auto_deref -> Bool
Informational methods.
=head2 generate_accessor -> CODE
Creates a new code reference for the attribute's accessor.
=head2 generate_predicate -> CODE
Creates a new code reference for the attribute's predicate.
=head2 generate_clearer -> CODE
Creates a new code reference for the attribute's clearer.
=head2 generate_handles -> { MethodName => CODE }
Creates a new code reference for each of the attribute's handles methods.
=head2 find_type_constraint -> CODE
Returns a code reference which can be used to check that a given value passes
this attribute's type constraint;
=head2 verify_type_constraint Item -> 1 | ERROR
Checks that the given value passes this attribute's type constraint. Returns 1
on success, otherwise C<confess>es.
=cut