perl6/doc/lib/Attribute
doc src
(title) class Attribute
class Attribute { }
In Perl 6 lingo, an I<attribute> refers to a per-instance/object storage slot.
An Attribute is used to talk about classes' and roles' attributes on the
meta level.
Normal usage of attributes does not require the user to use class Attribute
explicitly.
The usual way to obtain an object of type Attribute is by introspection:
class Useless {
has @!things;
}
my $a = Useless.^attributes(:local)[0];
say $a.name; # @!things
say $a.package; # Useless()
say $a.has-accessor; # False
# modifying an attribute from the outside
# this is usually not possible, but since Attribute
# is at the level of the meta class, all is fair game
my $instance = Useless.new;
$a.set_value($instance, [1, 2, 3]);
say $a.get_value($instance); # 1 2 3
Methods
(head2) name
method name(Attribute:D:) returns Str:D
Returns the name of the attribute. Note that this is always the private name,
so if an attribute is declared as has $.a , the name returned is $!a .
(head2) package
method package(Attribute:D:) returns Mu:U
Returns the package (class/grammar/role) to which this attribute belongs.
(head2) has-accessor
method has-accessor(Attribute:D:) returns Bool:D
Returns True if the attribute has a public accessor method.
(head2) readonly
method readonly(Attribute:D:) returns Bool:D
Returns True for readonly attributes, which is the default.
Returns False for attributes marked as is rw .
(head2) get_value
method get_value(Attribute:D: Mu $instance)
Returns the value stored in this attribute of object $instance .
Note that this method violates encapsulation of the object, and should be
used with care. Here be dragons.
(head2) set_value
method set_value(Attribute:D: Mu $instance, Mu \new_val)
Binds the value new_val to this attribute of object $instance .
Note that this method violates encapsulation of the object, and should be
used with care. Here be dragons.
