A description of the powerful features made possible by Qt’s dynamic object model.
The standard C++ object model provides very efficient runtime support for the object paradigm. But its static nature is inflexibile in certain problem domains. Graphical user interface programming is a domain that requires both runtime efficiency and a high level of flexibility. Qt provides this, by combining the speed of C++ with the flexibility of the Qt Object Model.
Qt 把这些特征添加到 C++：
a very powerful mechanism for seamless object communication called 信号和槽
queryable and designable 对象特性
powerful events and event filters
contextual string translation for internationalization
sophisticated interval driven timers that make it possible to elegantly integrate many tasks in an event-driven GUI
hierarchical and queryable 对象树 that organize object ownership in a natural way
guarded pointers (
QPointer) that are automatically set to 0 when the referenced object is destroyed, unlike normal C++ pointers which become dangling pointers when their objects are destroyeda dynamic cast that works across library boundaries.
support for custom type creation.
Many of these Qt features are implemented with standard C++ techniques, based on inheritance from
QObject. Others, like the object communication mechanism and the dynamic property system, require the 元对象系统 provided by Qt’s own Meta-Object Compiler (moc).The meta-object system is a C++ extension that makes the language better suited to true component GUI programming.
These classes form the basis of the Qt Object Model.
QMetaObject 类包含有关 Qt 对象的元信息。
The QMetaMethod class provides meta-data about a member function.
QMetaEnum 类提供有关枚举器的元数据。
The QMetaProperty class provides meta-data about a property.
QMetaClassInfo 类提供有关类的额外信息。
QMetaTypeQMetaType 类在 Meta-Object (元对象) 系统中管理命名类型。
Exception-safe wrapper around QObject::blockSignals().
QObject 类是所有 Qt 对象的基类。
QObjectCleanupHandlerQObjectCleanupHandler 类观察多个 QObject 的寿命。
QPointerThe QPointer class is a template class that provides guarded pointers to QObject.
QSignalMapper 类捆绑来自可识别发送器的信号。
PySide2.QtCore.QVariantQVariant 类充当用于最常见 Qt 数据类型的 Union (并集)。
Some of the added features listed above for the Qt Object Model, require that we think of Qt Objects as identities, not values. Values are copied or assigned; identities are cloned. Cloning means to create a new identity, not an exact copy of the old one. For example, twins have different identities. They may look identical, but they have different names, different locations, and may have completely different social networks.
Then cloning an identity is a more complex operation than copying or assigning a value. We can see what this means in the Qt Object Model.
A Qt Object…
might have a unique
objectName(). If we copy a Qt Object, what name should we give the copy?has a location in an object hierarchy . If we copy a Qt Object, where should the copy be located?
can be connected to other Qt Objects to emit signals to them or to receive signals emitted by them. If we copy a Qt Object, how should we transfer these connections to the copy?
can have new properties added to it at runtime that are not declared in the C++ class. If we copy a Qt Object, should the copy include the properties that were added to the original?
For these reasons, Qt Objects should be treated as identities, not as values. Identities are cloned, not copied or assigned, and cloning an identity is a more complex operation than copying or assigning a value. Therefore,
QObjectand all subclasses ofQObject(direct or indirect) have theircopy 构造函数 and assignment operatordisabled.
