QPluginLoader Class

成员函数

QPluginLoader::QPluginLoader(QObject *parent = Q_NULLPTR)

Constructs a plugin loader with the given parent.

QPluginLoader::QPluginLoader(const QString &fileName, QObject *parent = Q_NULLPTR)

Constructs a plugin loader with the given parent that will load the plugin specified by fileName.

To be loadable, the file's suffix must be a valid suffix for a loadable library in accordance with the platform, e.g. .so on Unix, - .dylib on macOS and iOS, and .dll on Windows. The suffix can be verified with QLibrary::isLibrary().

参见 setFileName().

QPluginLoader::~QPluginLoader()

Destroys the QPluginLoader object.

Unless unload() was called explicitly, the plugin stays in memory until the application terminates.

参见 isLoaded() and unload().

QString QPluginLoader::errorString() const

Returns a text string with the description of the last error that occurred.

This function was introduced in Qt 4.2.

QObject *QPluginLoader::instance()

Returns the root component object of the plugin. The plugin is loaded if necessary. The function returns 0 if the plugin could not be loaded or if the root component object could not be instantiated.

If the root component object was destroyed, calling this function creates a new instance.

The root component, returned by this function, is not deleted when the QPluginLoader is destroyed. If you want to ensure that the root component is deleted, you should call unload() as soon you don't need to access the core component anymore. When the library is finally unloaded, the root component will automatically be deleted.

The component object is a QObject. Use qobject_cast() to access interfaces you are interested in.

参见 load().

bool QPluginLoader::isLoaded() const

Returns true if the plugin is loaded; otherwise returns false.

参见 load().

bool QPluginLoader::load()

Loads the plugin and returns true if the plugin was loaded successfully; otherwise returns false. Since instance() always calls this function before resolving any symbols it is not necessary to call it explicitly. In some situations you might want the plugin loaded in advance, in which case you would use this function.

参见 unload().

QJsonObject QPluginLoader::metaData() const

Returns the meta data for this plugin. The meta data is data specified in a json format using the Q_PLUGIN_METADATA() macro when compiling the plugin.

The meta data can be queried in a fast and inexpensive way without actually loading the plugin. This makes it possible to e.g. store capabilities of the plugin in there, and make the decision whether to load the plugin dependent on this meta data.

[static] QObjectList QPluginLoader::staticInstances()

Returns a list of static plugin instances (root components) held by the plugin loader.

参见 staticPlugins().

[static] QVector<QStaticPlugin> QPluginLoader::staticPlugins()

Returns a list of QStaticPlugins held by the plugin loader. The function is similar to staticInstances() with the addition that a QStaticPlugin also contains meta data information.

参见 staticInstances().

bool QPluginLoader::unload()

Unloads the plugin and returns true if the plugin could be unloaded; otherwise returns false.

This happens automatically on application termination, so you shouldn't normally need to call this function.

If other instances of QPluginLoader are using the same plugin, the call will fail, and unloading will only happen when every instance has called unload().

Don't try to delete the root component. Instead rely on that unload() will automatically delete it when needed.

参见 instance() and load().