NAME
Class::XSAccessor - Generate fast XS accessors without runtime
compilation
SYNOPSIS
package MyClass;
use Class::XSAccessor
replace => 1, # Replace existing methods (if any)
constructor => 'new',
getters => {
get_foo => 'foo', # 'foo' is the hash key to access
get_bar => 'bar',
},
setters => {
set_foo => 'foo',
set_bar => 'bar',
},
accessors => {
foo => 'foo',
bar => 'bar',
},
predicates => {
has_foo => 'foo',
has_bar => 'bar',
},
lvalue_accessors => { # see below
baz => 'baz', # ...
},
true => [ 'is_token', 'is_whitespace' ],
false => [ 'significant' ];
# The imported methods are implemented in fast XS.
# normal class code here.
As of version 1.05, some alternative syntax forms are available:
package MyClass;
# Options can be passed as a HASH reference, if preferred,
# which can also help Perl::Tidy to format the statement correctly.
use Class::XSAccessor {
# If the name => key values are always identical,
# the following shorthand can be used.
accessors => [ 'foo', 'bar' ],
};
DESCRIPTION
Class::XSAccessor implements fast read, write and read/write accessors
in XS. Additionally, it can provide predicates such as "has_foo()" for
testing whether the attribute "foo" is defined in the object. It only
works with objects that are implemented as ordinary hashes.
Class::XSAccessor::Array implements the same interface for objects that
use arrays for their internal representation.
Since version 0.10, the module can also generate simple constructors
(implemented in XS). Simply supply the "constructor =>
'constructor_name'" option or the "constructors => ['new', 'create',
'spawn']" option. These constructors do the equivalent of the following
Perl code:
sub new {
my $class = shift;
return bless { @_ }, ref($class)||$class;
}
That means they can be called on objects and classes but will not clone
objects entirely. Parameters to "new()" are added to the object.
The XS accessor methods are between 3 and 4 times faster than typical
pure-Perl accessors in some simple benchmarking. The lower factor
applies to the potentially slightly obscure "sub set_foo_pp
{$_[0]->{foo} = $_[1]}", so if you usually write clear code, a factor of
3.5 speed-up is a good estimate. If in doubt, do your own benchmarking!
The method names may be fully qualified. The example in the synopsis
could have been written as "MyClass::get_foo" instead of "get_foo". This
way, methods can be installed in classes other than the current class.
See also: the "class" option below.
By default, the setters return the new value that was set, and the
accessors (mutators) do the same. This behaviour can be changed with the
"chained" option - see below. The predicates return a boolean.
Since version 1.01, "Class::XSAccessor" can generate extremely simple
methods which just return true or false (and always do so). If that
seems like a really superfluous thing to you, then consider a large
class hierarchy with interfaces such as PPI. These methods are provided
by the "true" and "false" options - see the synopsis.
OPTIONS
In addition to specifying the types and names of accessors, additional
options can be supplied which modify behaviour. The options are
specified as key/value pairs in the same manner as the accessor
declaration. For example:
use Class::XSAccessor
getters => {
get_foo => 'foo',
},
replace => 1;
The list of available options is:
replace
Set this to a true value to prevent "Class::XSAccessor" from complaining
about replacing existing subroutines.
chained
Set this to a true value to change the return value of setters and
mutators (when called with an argument). If "chained" is enabled, the
setters and accessors/mutators will return the object. Mutators called
without an argument still return the value of the associated attribute.
As with the other options, "chained" affects all methods generated in
the same "use Class::XSAccessor ..." statement.
class
By default, the accessors are generated in the calling class. The the
"class" option allows the target class to be specified.
LVALUES
Support for lvalue accessors via the keyword "lvalue_accessors" was
added in version 1.08. At this point, THEY ARE CONSIDERED HIGHLY
EXPERIMENTAL. Furthermore, their performance hasn't been benchmarked
yet.
The following example demonstrates an lvalue accessor:
package Address;
use Class::XSAccessor
constructor => 'new',
lvalue_accessors => { zip_code => 'zip' };
package main;
my $address = Address->new(zip => 2);
print $address->zip_code, "\n"; # prints 2
$address->zip_code = 76135; # <--- This is it!
print $address->zip_code, "\n"; # prints 76135
CAVEATS
Probably won't work for objects based on *tied* hashes. But that's a
strange thing to do anyway.
Scary code exploiting strange XS features.
If you think writing an accessor in XS should be a laughably simple
exercise, then please contemplate how you could instantiate a new XS
accessor for a new hash key that's only known at run-time. Note that
compiling C code at run-time a la Inline::C is a no go.
Threading. With version 1.00, a memory leak has been fixed. Previously,
a small amount of memory would leak if "Class::XSAccessor"-based classes
were loaded in a subthread without having been loaded in the "main"
thread. If the subthread then terminated, a hash key and an int per
associated method used to be lost. Note that this mattered only if
classes were only loaded in a sort of throw-away thread.
In the new implementation, as of 1.00, the memory will still not be
released, in the same situation, but it will be recycled when the same
class, or a similar class, is loaded again in any thread.
SEE ALSO
* Class::XSAccessor::Array
* AutoXS
AUTHORS
Steffen Mueller <smueller@cpan.org>
chocolateboy <chocolate@cpan.org>
COPYRIGHT AND LICENSE
Copyright (C) 2008-2020 by Steffen Mueller
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself, either Perl version 5.8 or, at your
option, any later version of Perl 5 you may have available.