QMetaObject¶

PyQt5.QtCore.QMetaObject

Description¶

The QMetaObject class contains meta-information about Qt objects.

The Qt Meta-Object System in Qt is responsible for the signals and slots inter-object communication mechanism, runtime type information, and the Qt property system. A single QMetaObject instance is created for each QObject subclass that is used in an application, and this instance stores all the meta-information for the QObject subclass. This object is available as metaObject().

This class is not normally required for application programming, but it is useful if you write meta-applications, such as scripting engines or GUI builders.

The functions you are most likely to find useful are these:

className() returns the name of a class.
superClass() returns the superclass’s meta-object.
method() and methodCount() provide information about a class’s meta-methods (signals, slots and other invokable member functions).
enumerator() and enumeratorCount() and provide information about a class’s enumerators.
propertyCount() and property() provide information about a class’s properties.
constructor() and constructorCount() provide information about a class’s meta-constructors.

The index functions indexOfConstructor(), indexOfMethod(), indexOfEnumerator(), and indexOfProperty() map names of constructors, member functions, enumerators, or properties to indexes in the meta-object. For example, Qt uses indexOfMethod() internally when you connect a signal to a slot.

Classes can also have a list of name–value pairs of additional class information, stored in QMetaClassInfo objects. The number of pairs is returned by classInfoCount(), single pairs are returned by classInfo(), and you can search for pairs with indexOfClassInfo().

Classes¶

Connection

Methods¶

__init__(): TODO

__init__(QMetaObject): TODO

@staticmethod checkConnectArgs(str, str) → bool: TODO

@staticmethod checkConnectArgs(QMetaMethod, QMetaMethod) → bool: TODO

classInfo(int) → QMetaClassInfo: TODO

classInfoCount() → int: TODO

classInfoOffset() → int: TODO

className() → str: Returns the class name.

See also

superClass().

@staticmethod connectSlotsByName(QObject): TODO

constructor(int) → QMetaMethod: TODO

constructorCount() → int: TODO

enumerator(int) → QMetaEnum: TODO

enumeratorCount() → int: TODO

enumeratorOffset() → int: TODO

indexOfClassInfo(str) → int: TODO

indexOfConstructor(str) → int: TODO

indexOfEnumerator(str) → int: TODO

indexOfMethod(str) → int: TODO

indexOfProperty(str) → int: TODO

indexOfSignal(str) → int: TODO

indexOfSlot(str) → int: TODO

inherits(QMetaObject) → bool: TODO

@staticmethod invokeMethod(QObject, str, value0: QGenericArgument = QGenericArgument(0,0), value1: QGenericArgument = QGenericArgument(0,0), value2: QGenericArgument = QGenericArgument(0,0), value3: QGenericArgument = QGenericArgument(0,0), value4: QGenericArgument = QGenericArgument(0,0), value5: QGenericArgument = QGenericArgument(0,0), value6: QGenericArgument = QGenericArgument(0,0), value7: QGenericArgument = QGenericArgument(0,0), value8: QGenericArgument = QGenericArgument(0,0), value9: QGenericArgument = QGenericArgument(0,0)) → object: TODO

@staticmethod invokeMethod(QObject, str, QGenericReturnArgument, value0: QGenericArgument = QGenericArgument(0,0), value1: QGenericArgument = QGenericArgument(0,0), value2: QGenericArgument = QGenericArgument(0,0), value3: QGenericArgument = QGenericArgument(0,0), value4: QGenericArgument = QGenericArgument(0,0), value5: QGenericArgument = QGenericArgument(0,0), value6: QGenericArgument = QGenericArgument(0,0), value7: QGenericArgument = QGenericArgument(0,0), value8: QGenericArgument = QGenericArgument(0,0), value9: QGenericArgument = QGenericArgument(0,0)) → object: TODO

@staticmethod invokeMethod(QObject, str, ConnectionType, value0: QGenericArgument = QGenericArgument(0,0), value1: QGenericArgument = QGenericArgument(0,0), value2: QGenericArgument = QGenericArgument(0,0), value3: QGenericArgument = QGenericArgument(0,0), value4: QGenericArgument = QGenericArgument(0,0), value5: QGenericArgument = QGenericArgument(0,0), value6: QGenericArgument = QGenericArgument(0,0), value7: QGenericArgument = QGenericArgument(0,0), value8: QGenericArgument = QGenericArgument(0,0), value9: QGenericArgument = QGenericArgument(0,0)) → object: TODO

@staticmethod invokeMethod(QObject, str, ConnectionType, QGenericReturnArgument, value0: QGenericArgument = QGenericArgument(0,0), value1: QGenericArgument = QGenericArgument(0,0), value2: QGenericArgument = QGenericArgument(0,0), value3: QGenericArgument = QGenericArgument(0,0), value4: QGenericArgument = QGenericArgument(0,0), value5: QGenericArgument = QGenericArgument(0,0), value6: QGenericArgument = QGenericArgument(0,0), value7: QGenericArgument = QGenericArgument(0,0), value8: QGenericArgument = QGenericArgument(0,0), value9: QGenericArgument = QGenericArgument(0,0)) → object

Invokes the member (a signal or a slot name) on the object obj. Returns true if the member could be invoked. Returns false if there is no such member or the parameters did not match.

The invocation can be either synchronous or asynchronous, depending on type:

If type is DirectConnection, the member will be invoked immediately.
If type is QueuedConnection, a QEvent will be sent and the member is invoked as soon as the application enters the main event loop.
If type is BlockingQueuedConnection, the method will be invoked in the same way as for QueuedConnection, except that the current thread will block until the event is delivered. Using this connection type to communicate between objects in the same thread will lead to deadlocks.
If type is AutoConnection, the member is invoked synchronously if obj lives in the same thread as the caller; otherwise it will invoke the member asynchronously.

The return value of the member function call is placed in ret. If the invocation is asynchronous, the return value cannot be evaluated. You can pass up to ten arguments (val0, val1, val2, val3, val4, val5, val6, val7, val8, and val9) to the member function.

QGenericArgument and QGenericReturnArgument are internal helper classes. Because signals and slots can be dynamically invoked, you must enclose the arguments using the Q_ARG() and Q_RETURN_ARG() macros. Q_ARG() takes a type name and a const reference of that type; Q_RETURN_ARG() takes a type name and a non-const reference.

You only need to pass the name of the signal or slot to this function, not the entire signature. For example, to asynchronously invoke the quit() slot on a QThread, use the following code:

# QMetaObject::invokeMethod(thread, "quit",
#                           Qt::QueuedConnection);

With asynchronous method invocations, the parameters must be of types that are known to Qt’s meta-object system, because Qt needs to copy the arguments to store them in an event behind the scenes. If you try to use a queued connection and get the error message

# QMetaObject::invokeMethod: Unable to handle unregistered datatype 'MyType'

call qRegisterMetaType() to register the data type before you call .

To synchronously invoke the compute(QString, int, double) slot on some arbitrary object obj retrieve its return value:

# QString retVal;
# QMetaObject::invokeMethod(obj, "compute", Qt::DirectConnection,
#                           Q_RETURN_ARG(QString, retVal),
#                           Q_ARG(QString, "sqrt"),
#                           Q_ARG(int, 42),
#                           Q_ARG(double, 9.7));

If the “compute” slot does not take exactly one QString, one int and one double in the specified order, the call will fail.