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NOCpulse::PersistentObject.3pm

NAME

NOCpulse::PersistentObject - an abstract PERL class that provides a primitive persistence mechanism for named objects.

SYNOPSIS

         package MyClass;
         use NOCpulse::PersistentObject;
         @ISA qw(NOCpulse::PersistentObject);
         ...
         my $thing = NOCpulse::PersistentObject->newInitializedNamed('hello');
         $thing->persist;
         $sameThing = NOCpulse::PersistentObject->loadFromDatabase('hello');
 
 

DESCRIPTION

NOCpulse::PersistentObject is a layer above Object that adds primitive object persistence via the FreezeThaw based serialization mechanism defined in Object.

To set up this mechanism, you must:

* Set up an Object::SystemIni() file for the class hierarchy

And for each class you must:

* Add a section to the SystemIni file whose name is the name of your class

* Add an item to that section called ``databaseDirectory'' whose value is
  a path to the directory where the instance database is to live

* Add an item to that section called ``databaseType'' whose value is the
  name of a properly fleshed out subclass of AbstractObjectRepository (for instance
  NOCpulse::DBMObjectRepository).

Classes derived from NOCpulse::PersistentObject will have an instance variable called ``name'' defined for them. The name variable is the means by which the persistence mechanism keeps track of stored objects. You must come up with a scheme that ensures that each instance of a given class has a name value that is unique among all instances.

Insofar as the name attribute is crucial to the inner workings of the persistence mechanisms, a number of new constructors are defined:

newNamed(<name>) newInitializedName(<name>[,@opts]) loadFromDatabase(<name>)

You should use these instead of the Object constructors to ensure that the persistence mechanism has everything set up properly.

REQUIRES

Object

EXPORTS

nothing

MODULE VARIABLES

$config - holds an Config::IniFiles instance if one was created with SystemIni()

CLASS VARIABLES

%classvars - holds hashes of ``class instance'' variables

MODULE METHODS

none

CLASS METHODS

databaseType()

Returns the name of the database type used to store objects of this class (as currently configured)

databaseDirectory()

Returns the path of the directory in which the databaseType will store objects of this class (as currently configured). Looks first for a class variable called databaseDirectory, then at the class ini section for an entry called databaseDirectory.

databaseFilename()

Returns the full path name of the file that databaseType will store objects in.

database()

Returns the database instance for this class

instances()

Returns a hash of all the instances of the class currently in memory

named(<name>)

Returns the instance named <name> if it is currently in memory

saveToDatabase()

Saves all objects currently in memory to the repository. Also see persist() (below)

loadFromDatabase([<name> [, <use-cache]])

If called with no parameters, loads all objects from the repository into memory and returns a pointer to the instances() hash

If called with the <name> parameter, loads the named object from the repository into memory (adding it to the instances list) and returns the instance.

If called with <name> and <use-cache>, first checks for a cached instances and returns it if present, otherwise loads as above.

newNamed(<name>)

Creates an instance of the class whose name is <name> in memory and returns it.

newNamed(<name>[,@params])

Creates an instance of the class whos name is <name> in memory, calls its initialize() method with [@params], and returns the instance.

INSTANCE METHODS

instVarDefinitions()

Same as that for Object, but Subclasses MUST call $self-SUPER::instVarDefinitions> if they override this.

persist()

Writes the instance in question to the object repository immediately.

doesNotUnderstand(...)

Overrides AUTOLOADed get_xxx in Object behavior such that instances can retrieve values from its class .ini file on a per instance basis.

Explanation: If you set up a per-class .ini file according to Object::ConfigValue(), you this extension to the get_xxx protocol allows you to exploit the fact that all instances of NOCpulse::PersistentObject have a unique name. Specifically, once you have an instantiated NOCpulse::PersistentObject, a call to get_xxx (where xxx is any name) that would otherwise fail for the lack of an instance variable will now first check to see if your class per-class .ini file has a section whose name is the name of the current instance. If such a section is found, its namespace will be ``added'' to that of the instance virtually via the get_xxx call.

POD ERRORS

Hey! The above document had some coding errors, which are explained below:

Around line 304:

You forgot a '=back' before '=head1'

Around line 392:

You forgot a '=back' before '=head1'