Add a variable to a class instance at runtime: Difference between revisions
Add a variable to a class instance at runtime (view source)
Revision as of 23:33, 16 July 2011
, 12 years ago→{{header|Perl 6}}: Add Perl 6 example
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Thundergnat (talk | contribs) (→{{header|Perl 6}}: Add Perl 6 example) |
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# Set runtime variable (key => value).
$o->{'foo'} = 1;</lang>
=={{header|Perl 6}}==
You can add variables/methods to a class at runtime by composing in a role. The role only affects that instance, though it is inheritable. An object created from an existing object will inherit any roles composed in with values set to those at the time the role was created. If you want to keep changed values in the new object, clone it instead.
<lang perl6>class Bar { } # an empty class
my $object = Bar.new; # new instance
role a_role { # role to add a variable: foo,
has $.foo is rw = 2; # with an initial value of 2
}
$object does a_role; # compose in the role
say $object.foo; # prints: 2
$object.foo = 5; # change the variable
say $object.foo; # prints: 5
my $ohno = Bar.new; # new Bar object
#say $ohno.foo; # runtime error, base Bar class doesn't have the variable foo
my $this = $object.new; # instantiate a new Bar derived from $object
say $this.foo; # prints: 2 - original role value
my $that = $object.clone; # instantiate a new Bar derived from $object copying any variables
say $that.foo; # 5 - value from the cloned object</lang>
=={{header|PHP}}==
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