Umbrello::PluginLoader Class Reference

#include <pluginloader.h>

Inheritance diagram for Umbrello::PluginLoader:

Collaboration diagram for Umbrello::PluginLoader:

Public Types
typedef Q3ValueList< Plugin * >	PluginList
typedef QMap< QString, Plugin * >	PluginMap
typedef QMap< QString, PluginList >	CategoryMap

Public Member Functions
	~PluginLoader ()
Plugin *	loadPlugin (const QString &name)
Plugin *	findPlugin (const QString &name)
void	unloadPlugin (const QString &name)
const PluginMap &	plugins () const
const CategoryMap &	categories () const

Static Public Member Functions
static PluginLoader *	instance ()

Private Slots
void	slotDestroyed (QObject *obj)

Private Member Functions
	PluginLoader ()

Private Attributes
PluginMap	_plugins
	The plugin mapping. More...
CategoryMap	_categories
	Categories of plugins. More...

Static Private Attributes
static PluginLoader *	_instance = 0
	Singleton instance. More...

Detailed Description

The plugin loader is an abstraction that sits on top of KLibLoader. Whereas plugins are specialized shared objects, the plugin must specialize the loading of those objects. Essentially, the plugin loader provides a single unit of functionality - loading plugins. In order to load a plugin, we must first load a shared library and then use the libraries factory to create the plugin. However, because a plugin is required to be a singleton, we must ensure that no plugin is ever created more than once. To that end, the loader must also retain a map of loaded plugins. When a loaded plugin is requested, we can increase its reference count.

On the subject of unloading, we actually have very little to do. The unload method on a plugin is simply a reference decrementer. When it reaches 0, the object destroys itself. Being a QObject, it will emit the destroyed signal just before deletion, allowing the plugin loader to respond to the event and remove the plugin from its mapping.

The PluginLoader also manages categories of plugins. The runtime categories actually reflect the directory structure of the build environment with each category represented by the name of a directory. The categories are "pre-seeded" at startup.

Bug:

Plugins are not removed from their respective categories when they are destroyed. It may be acceptable to call Plugin::category() from slotDestroyed because the category() method doesn't reference any local variables - it just returns a string.

Member Typedef Documentation

CategoryMap

typedef QMap<QString, PluginList> Umbrello::PluginLoader::CategoryMap

Container of plugin categories

PluginList

typedef Q3ValueList<Plugin *> Umbrello::PluginLoader::PluginList

Just a container of plugins

PluginMap

typedef QMap<QString, Plugin *> Umbrello::PluginLoader::PluginMap

The containment type for mapping plugins

Constructor & Destructor Documentation

~PluginLoader()

PluginLoader::~PluginLoader

(

)

Destroy the plugin loader

PluginLoader()

PluginLoader::PluginLoader ( )

private

Private constructor - This must be created through the instance method

Member Function Documentation

categories()

const PluginLoader::CategoryMap & PluginLoader::categories

(

)

const

Get a reference to the plugin category mapping.

findPlugin()

Plugin * PluginLoader::findPlugin

(

const QString &

name

)

Find a plugin

instance()

PluginLoader * PluginLoader::instance ( )

static

Singleton accessor

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loadPlugin()

Plugin * PluginLoader::loadPlugin

(

const QString &

name

)

Load a plugin. Test to see if the plugin already exists. If it does, just add a reference to it and continue on.

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plugins()

const PluginLoader::PluginMap & PluginLoader::plugins

(

)

const

Get a reference to the plugin mapping. This method wraps everything in consts with the express purpose that no changes are made to the plugin map after using this method.

slotDestroyed

void PluginLoader::slotDestroyed ( QObject *  obj )

privateslot

This is used to connect to the destroyed signal emitted by plugins when they are finally deleted. The plugin loader uses this signal to remove the plugin from the plugin map.

unloadPlugin()

void PluginLoader::unloadPlugin

(

const QString &

name

)

Unload a plugin. Never use this method. It is only used by the deref method of a plugin to cause this class to unload the corresponding library. In fact, there is actually no corresponding plugin to unload, we just unload the library.

Member Data Documentation

_categories

CategoryMap Umbrello::PluginLoader::_categories

private

Categories of plugins.

_instance

PluginLoader * PluginLoader::_instance = 0

staticprivate

Singleton instance.

_plugins

PluginMap Umbrello::PluginLoader::_plugins

private

The plugin mapping.

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The documentation for this class was generated from the following files:

• umbrello/_unused/pluginloader.h
• umbrello/_unused/pluginloader.cpp