Object::Accessor - interface to create per object accessors
- ### using the object
- $obj = Object::Accessor->new; # create object
- $obj = Object::Accessor->new(@list); # create object with accessors
- $obj = Object::Accessor->new(\%h); # create object with accessors
- # and their allow handlers
- $bool = $obj->mk_accessors('foo'); # create accessors
- $bool = $obj->mk_accessors( # create accessors with input
- {foo => ALLOW_HANDLER} ); # validation
- $bool = $obj->mk_aliases( # create an alias to an existing
- alias_name => 'method'); # method name
- $clone = $obj->mk_clone; # create a clone of original
- # object without data
- $bool = $obj->mk_flush; # clean out all data
- @list = $obj->ls_accessors; # retrieves a list of all
- # accessors for this object
- $bar = $obj->foo('bar'); # set 'foo' to 'bar'
- $bar = $obj->foo(); # retrieve 'bar' again
- $sub = $obj->can('foo'); # retrieve coderef for
- # 'foo' accessor
- $bar = $sub->('bar'); # set 'foo' via coderef
- $bar = $sub->(); # retrieve 'bar' by coderef
- ### using the object as base class
- package My::Class;
- use base 'Object::Accessor';
- $obj = My::Class->new; # create base object
- $bool = $obj->mk_accessors('foo'); # create accessors, etc...
- ### make all attempted access to non-existent accessors fatal
- ### (defaults to false)
- $Object::Accessor::FATAL = 1;
- ### enable debugging
- $Object::Accessor::DEBUG = 1;
- ### advanced usage -- callbacks
- { my $obj = Object::Accessor->new('foo');
- $obj->register_callback( sub { ... } );
- $obj->foo( 1 ); # these calls invoke the callback you registered
- $obj->foo() # which allows you to change the get/set
- # behaviour and what is returned to the caller.
- }
- ### advanced usage -- lvalue attributes
- { my $obj = Object::Accessor::Lvalue->new('foo');
- print $obj->foo = 1; # will print 1
- }
- ### advanced usage -- scoped attribute values
- { my $obj = Object::Accessor->new('foo');
- $obj->foo( 1 );
- print $obj->foo; # will print 1
- ### bind the scope of the value of attribute 'foo'
- ### to the scope of '$x' -- when $x goes out of
- ### scope, 'foo's previous value will be restored
- { $obj->foo( 2 => \my $x );
- print $obj->foo, ' ', $x; # will print '2 2'
- }
- print $obj->foo; # will print 1
- }
Object::Accessor
provides an interface to create per object
accessors (as opposed to per Class
accessors, as, for example,
Class::Accessor
provides).
You can choose to either subclass this module, and thus using its
accessors on your own module, or to store an Object::Accessor
object inside your own object, and access the accessors from there.
See the SYNOPSIS
for examples.
Creates a new (and empty) Object::Accessor
object. This method is
inheritable.
Any arguments given to new
are passed straight to mk_accessors
.
If you want to be able to assign to your accessors as if they
were lvalue
s, you should create your object in the
Object::Accessor::Lvalue
namespace instead. See the section
on LVALUE ACCESSORS
below.
Creates a list of accessors for this object (and NOT
for other ones
in the same class!).
Will not clobber existing data, so if an accessor already exists,
requesting to create again is effectively a no-op.
When providing a hashref
as argument, rather than a normal list,
you can specify a list of key/value pairs of accessors and their
respective input validators. The validators can be anything that
Params::Check
's allow
function accepts. Please see its manpage
for details.
For example:
- $object->mk_accessors( {
- foo => qr/^\d+$/, # digits only
- bar => [0,1], # booleans
- zot => \&my_sub # a custom verification sub
- } );
Returns true on success, false on failure.
Accessors that are called on an object, that do not exist return
undef by default, but you can make this a fatal error by setting the
global variable $FATAL
to true. See the section on GLOBAL
VARIABLES
for details.
Note that you can bind the values of attributes to a scope. This allows
you to temporarily
change a value of an attribute, and have it's
original value restored up on the end of it's bound variable's scope;
For example, in this snippet of code, the attribute foo
will
temporarily be set to 2
, until the end of the scope of $x
, at
which point the original value of 1
will be restored.
- my $obj = Object::Accessor->new;
- $obj->mk_accessors('foo');
- $obj->foo( 1 );
- print $obj->foo; # will print 1
- ### bind the scope of the value of attribute 'foo'
- ### to the scope of '$x' -- when $x goes out of
- ### scope, 'foo' previous value will be restored
- { $obj->foo( 2 => \my $x );
- print $obj->foo, ' ', $x; # will print '2 2'
- }
- print $obj->foo; # will print 1
Note that all accessors are read/write for everyone. See the TODO
section for details.
Returns a list of accessors that are supported by the current object.
The corresponding coderefs can be retrieved by passing this list one
by one to the can
method.
Returns the allow handler for the given key, which can be used with
Params::Check
's allow()
handler. If there was no allow handler
specified, an allow handler that always returns true will be returned.
Creates an alias for a given method name. For all intents and purposes, these two accessors are now identical for this object. This is akin to doing the following on the symbol table level:
- *alias = *method
This allows you to do the following:
- $self->mk_accessors('foo');
- $self->mk_aliases( bar => 'foo' );
- $self->bar( 42 );
- print $self->foo; # will print 42
Makes a clone of the current object, which will have the exact same accessors as the current object, but without the data stored in them.
Flushes all the data from the current object; all accessors will be
set back to their default state of undef.
Returns true on success and false on failure.
Checks if all values in the current object are in accordance with their own allow handler. Specifically useful to check if an empty initialised object has been filled with values satisfying their own allow criteria.
This method allows you to register a callback, that is invoked every time an accessor is called. This allows you to munge input data, access external data stores, etc.
You are free to return whatever you wish. On a set
call, the
data is even stored in the object.
Below is an example of the use of a callback.
- $object->some_method( "some_value" );
- my $callback = sub {
- my $self = shift; # the object
- my $meth = shift; # "some_method"
- my $val = shift; # ["some_value"]
- # could be undef -- check 'exists';
- # if scalar @$val is empty, it was a 'get'
- # your code here
- return $new_val; # the value you want to be set/returned
- }
To access the values stored in the object, circumventing the
callback structure, you should use the ___get
and ___set
methods
documented further down.
This method overrides UNIVERAL::can
in order to provide coderefs to
accessors which are loaded on demand. It will behave just like
UNIVERSAL::can
where it can -- returning a class method if it exists,
or a closure pointing to a valid accessor of this particular object.
You can use it as follows:
- $sub = $object->can('some_accessor'); # retrieve the coderef
- $sub->('foo'); # 'some_accessor' now set
- # to 'foo' for $object
- $foo = $sub->(); # retrieve the contents
- # of 'some_accessor'
See the SYNOPSIS
for more examples.
Method to directly access the value of the given accessor in the object. It circumvents all calls to allow checks, callbacks, etc.
Use only if you Know What You Are Doing
! General usage for
this functionality would be in your own custom callbacks.
Method to directly set the value of the given accessor in the object. It circumvents all calls to allow checks, callbacks, etc.
Use only if you Know What You Are Doing
! General usage for
this functionality would be in your own custom callbacks.
Method to directly alias one accessor to another for this object. It circumvents all sanity checks, etc.
Use only if you Know What You Are Doing
!
Object::Accessor
supports lvalue
attributes as well. To enable
these, you should create your objects in the designated namespace,
Object::Accessor::Lvalue
. For example:
will actually print 1
and work as expected. Since this is an
optional feature, that's not desirable in all cases, we require
you to explicitly use the Object::Accessor::Lvalue
class.
Doing the same on the standard Object
>Accessor> class would
generate the following code & errors:
- my $obj = Object::Accessor->new('foo');
- $obj->foo += 1;
- Can't modify non-lvalue subroutine call
Note that lvalue
support on AUTOLOAD
routines is a
perl 5.8.x
feature. See perldoc perl58delta for details.
Due to the nature of lvalue subs
, we never get access to the
value you are assigning, so we can not check it against your allow
handler. Allow handlers are therefor unsupported under lvalue
conditions.
See perldoc perlsub
for details.
Due to the nature of lvalue subs
, we never get access to the
value you are assigning, so we can not check provide this value
to your callback. Furthermore, we can not distinguish between
a get
and a set
call. Callbacks are therefor unsupported
under lvalue
conditions.
See perldoc perlsub
for details.
Set this variable to true to make all attempted access to non-existent
accessors be fatal.
This defaults to false
.
Set this variable to enable debugging output.
This defaults to false
.
Currently all accessors are read/write for everyone. Perhaps a future release should make it possible to have read-only accessors as well.
If you use codereferences for your allow handlers, you will not be able
to freeze the data structures using Storable
.
Due to a bug in storable (until at least version 2.15), qr// compiled
regexes also don't de-serialize properly. Although this bug has been
reported, you should be aware of this issue when serializing your objects.
You can track the bug here:
- http://rt.cpan.org/Ticket/Display.html?id=1827
Please report bugs or other issues to <bug-object-accessor@rt.cpan.org>.
This module by Jos Boumans <kane@cpan.org>.
This library is free software; you may redistribute and/or modify it under the same terms as Perl itself.