++ed by:

2 PAUSE users
1 non-PAUSE user.

Sergey Aleynikov
and 1 contributors


Class::Accessor::Inherited::XS - Fast XS inherited, object and class accessors


  # install accessors at compile time
  use Class::Accessor::Inherited::XS 
      package      => 'Pkg', # optionally install into another package
      constructor  => 'new', # object constructor name
      inherited    => 'foo', # inherited accessor for class/object
      object       => 'foo', # non-inherited simple object accessor
      varclass     => 'foo', # non-inherited accessor for __PACKAGE__,  aliased with '$__PACKAGE__::foo' variable
      class        => 'foo', # non-inherited anonymous accessor for __PACKAGE__
  use Class::Accessor::Inherited::XS {  # optional braces
      inherited => {foo => 'foo_key'},  # change package variable/hash key
      object    => {foo => 'foo_key'},  # change hash key
      class_ro  => {foo => $default},   # class_ro, varclass_ro, class, varclass set default values instead
      class     => {foo => $subref},    # lazy accessor initializer
      varclass  => ['foo', 'bar'],      # provide a list of accessor names
      accessors => ['foo'],             # alias for 'object'
      getters   => ['foo'],             # alias for 'object_ro'

  # Or if you prefer a Class::Accessor::Grouped-like interface, you can do it
  # at run time. Note that this is not recommended and provides limited feature set.
  use parent 'Class::Accessor::Inherited::XS::Compat';

  __PACKAGE__->mk_inherited_accessors('foo', [bar => 'bar_key']);


This module provides a very fast implementation for a wide range of accessor types.

inherited accessors have been introduced by Class::Accessor::Grouped. They allow you to override values set in a parent class with values set in childs or object instances. This module tries to be compatible with Class::Accessor::Grouped as much as possible.

Since this module focuses primary on speed, it provides no means to have your own per-class getters/setters logic (like overriding "get_inherited" in Class::Accessor::Grouped / "set_inherited" in Class::Accessor::Grouped), but it allows you to create new inherited accesor types with an attached callback.

class and varclass accessors are non-inherited package accessors - they return values from the class they were defined in, even when called on objects or child classes. The difference between them is that the varclass internal storage is a package variable with the same name, while class stores it's value in an anonymous variable.

object accessors provides plain simple hash key access.

class_ro, varclass_ro, inherited_ro, object_ro are readonly counterparts for correspoding accessors without _ro suffix. They behave exactly the same except that they will croak upon a call with arguments. To set values for such accessors, you can write to either corresponding package variable or a hash key. ro_class accessor has no externally accessible storage, but you can provide a default value for it using hash initializer syntax.

lazy accessors do not have their own keyword but, instead, if you pass a subref as a default argument to any one of the package accessors' family, it's not stored as-is, but is called instead upon the first accessor read and it's return value is stored. After that, lazy accessor becomes a normal one of the same type. Calling an accessor as a setter before first getter will loose it's defaultness (unless, of course, it's a readonly one).

constructor can create objects either from a list or from a single hashref. Note that if you pass a hash reference, it becomes blessed too. If that's not what you want, pass a dereferenced copy. As a special case, passing a single undef returns you an empty object.

    __PACKAGE__->new(foo => 1, bar => 2); # values are copied
    __PACKAGE__->new(\%args);             # values are not copied, much faster
    $obj->new(foo => 1, bar => 2);        # values are copied, but nothing is taken from $obj
    $obj->new(\%args);                    # values are not copied, and nothing is taken from $obj


Starting with the perl 5.16.0, this module provides full support for UTF-8 method names and hash keys. But on older perls you can't distinguish UTF-8 strings from bytes string in method names, so accessors with UTF-8 names can end up getting a wrong value. You have been warned.

Also, starting from 5.16.0 accessor installation is binary safe, except for the Windows platform. This module croaks on attempts to install binary accessors on unsupported platforms.


Though highly discouraged, perl threads are supported by Class::Accessor::Inherited::XS. You can have accessors with same names pointing to different keys in different threads, etc. There are no known conceptual leaks.


Class::Accessor::Inherited::XS is at least 10x times faster than Class::Accessor::Grouped, depending on your usage pattern. Inherited accessors have constant speed even in large inheritance chains. Object accessors are even faster than Class::XSAccessor ones.

Accessors with just an empty sub callback are ~3x times slower then normal ones, so use them only when absolutely necessary.

Here are results from a benchmark run on perl 5.20.1 (see bench folder):

                       Rate pkg_gparent_cag pkg_cag obj_cag obj_caix_cb pkg_set_caix pkg_gparent_caix pkg_caix obj_cxa obj_caix obj_direct class_caix
pkg_gparent_cag    233829/s              --    -77%    -82%        -96%         -98%             -98%     -98%    -99%     -99%       -99%       -99%
pkg_cag           1022855/s            337%      --    -21%        -84%         -89%             -90%     -90%    -94%     -95%       -96%       -97%
obj_cag           1302727/s            457%     27%      --        -80%         -86%             -87%     -87%    -92%     -94%       -95%       -96%
obj_caix_cb       6377179/s           2627%    523%    390%          --         -33%             -36%     -37%    -62%     -69%       -76%       -80%
pkg_set_caix      9538400/s           3979%    833%    632%         50%           --              -4%      -6%    -43%     -54%       -64%       -70%
pkg_gparent_caix  9914704/s           4140%    869%    661%         55%           4%               --      -2%    -41%     -52%       -62%       -68%
pkg_caix         10138654/s           4236%    891%    678%         59%           6%               2%       --    -40%     -51%       -61%       -68%
obj_cxa          16858257/s           7110%   1548%   1194%        164%          77%              70%      66%      --     -19%       -36%       -46%
obj_caix         20811071/s           8800%   1935%   1498%        226%         118%             110%     105%     23%       --       -20%       -34%
obj_direct       26145035/s          11081%   2456%   1907%        310%         174%             164%     158%     55%      26%         --       -16%
class_caix       31300776/s          13286%   2960%   2303%        391%         228%             216%     209%     86%      50%        20%         --


    package MyAccessor;
    # 'register_type' isn't exported
    use Class::Accessor::Inherited::XS::Constants;
        inherited_cb => {on_read => sub {}, on_write => sub{}, opts => $bitset},

    package MyClass;
    use MyAccessor;
    use Class::Accessor::Inherited::XS {
        inherited    => ['foo'],
        inherited_cb => ['bar'],

You can register new inherited accessor types with associated read/write callbacks. Unlike Class::Accessor::Grouped, only a single callback can be set for a type, without per-class get_$type/set_$type lookups. You can omit either on_read or on_write if you don't need it to avoid performance losses from associated call.

on_read callback receives a single argument - return value from the underlying inherited accessor. It's result is the new accessor's return value (and it isn't stored anywhere).

on_write callback receives original accessor's arguments, and it's return value is stored as usual. Exceptions thrown from this callback will cancel store and will leave old value unchanged.

You can specify additional flags with the 'opts' key. Currently only IsNamed is supported - with it the accessor callback is invoked with it's name passed as an additional argument. This can be useful when creating a proxy.


To perform it's task, Devel::NYTProf hooks into the perl interpreter by replacing default behaviour for subroutine calls at the opcode level. To squeeze last bits of performance, Class::Accessor::Inherited::XS does the same, but separately on each call site of its accessors. It turns out into CAIX favor - Devel::NYTProf sees only the first call to CAIX accessor, but all subsequent ones become invisible to the subs profiler.

Note that the statement profiler still correctly accounts for the time spent on each line, you just don't see time spent in accessors' calls separately. That's sometimes OK, sometimes not - you get profile with all possible optimizations on, but it's not easy to comprehend.

Since it's hard to detect Devel::NYTProf (and any other module doing such magic) in a portable way (all hail Win32), there's an %ENV switch available - you can set CAIXS_DISABLE_ENTERSUB to a true value to disable opcode optimizations and get a full subs profile.


When using varclass accessors, do not clear or alias *__PACKAGE__::accessor glob - that will break aliasing between accessor storage and $__PACKAGE__::accessor variable. While the stored value is still accessible through accessor, it effectively becomes a class one.



Copyright (C) 2009 by Vladimir Timofeev

Copyright (C) 2014-2018 by Sergey Aleynikov

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.10.1 or, at your option, any later version of Perl 5 you may have available.