QPluginLoader ¶

概要 ¶

详细描述 ¶

QPluginLoader provides access to a Qt plugin. A Qt plugin is stored in a shared library (a DLL) and offers these benefits over shared libraries accessed using QLibrary :

• QPluginLoader checks that a plugin is linked against the same version of Qt as the application.

• QPluginLoader provides direct access to a root component object ( instance() ), instead of forcing you to resolve a C function manually.

An instance of a QPluginLoader object operates on a single shared library file, which we call a plugin. It provides access to the functionality in the plugin in a platform-independent way. To specify which plugin to load, either pass a file name in the constructor or set it with setFileName() .

最重要功能是 load() to dynamically load the plugin file, isLoaded() to check whether loading was successful, and instance() to access the root component in the plugin. The instance() function implicitly tries to load the plugin if it has not been loaded yet. Multiple instances of QPluginLoader can be used to access the same physical plugin.

Once loaded, plugins remain in memory until all instances of QPluginLoader has been unloaded, or until the application terminates. You can attempt to unload a plugin using unload() , but if other instances of QPluginLoader are using the same library, the call will fail, and unloading will only happen when every instance has called unload() . Right before the unloading happens, the root component will also be deleted.

See How to Create Qt Plugins for more information about how to make your application extensible through plugins.

注意： QPluginLoader cannot be used if your application is statically linked against Qt. In this case, you will also have to link to plugins statically. You can use QLibrary if you need to load dynamic libraries in a statically linked application.

另请参阅

QLibrary 插件 & 描绘范例

class QPluginLoader ( [ parent=None ] ) ¶

QPluginLoader(fileName[, parent=None])

param parent

QObject

param fileName

unicode

构造插件加载器采用给定 parent .

构造插件加载器采用给定 parent 将加载指定插件通过 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 在 Unix， .dylib 在 macOS 和 iOS，及 .dll 在 Windows。可以验证后缀采用 isLibrary() .

另请参阅

setFileName()

PySide2.QtCore.QPluginLoader. errorString ( ) ¶

返回类型

unicode

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

PySide2.QtCore.QPluginLoader. fileName ( ) ¶

返回类型

unicode

另请参阅

setFileName()

PySide2.QtCore.QPluginLoader. instance ( ) ¶

返回类型

QObject

返回插件的根组件对象。插件被加载若有必要。函数返回 None 若插件无法被加载或根组件对象无法被实例化。

若根组件对象被销毁，调用此函创建新实例。

不会删除由此函数返回的根组件当 QPluginLoader 被销毁时。若想要确保删除根组件，应该调用 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.

组件对象是 QObject 。使用 qobject_cast() to access interfaces you are interested in.

另请参阅

load()

PySide2.QtCore.QPluginLoader. isLoaded ( ) ¶

返回类型

bool

返回 true 若插件被加载；否则返回 false .

另请参阅

load()

PySide2.QtCore.QPluginLoader. load ( ) ¶

返回类型

bool

加载插件并返回 true 若插件加载成功；否则返回 false 。由于 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.

另请参阅

unload()

PySide2.QtCore.QPluginLoader. metaData ( ) ¶

返回类型

QJsonObject

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.

PySide2.QtCore.QPluginLoader. setFileName ( fileName ) ¶

参数

fileName – unicode

另请参阅

fileName()

static PySide2.QtCore.QPluginLoader. staticInstances ( ) ¶

返回类型

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

另请参阅

staticPlugins()

PySide2.QtCore.QPluginLoader. unload ( ) ¶

返回类型

bool

卸载插件并返回 true 若插件可以被卸载；否则返回 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 .

Don’t try to delete the root component. Instead rely on that will automatically delete it when needed.

另请参阅

instance() load()