QMetaObject

The QMetaObject class contains meta-information about Qt objects. More…

Inheritance diagram of PySide2.QtCore.QMetaObject

Synopsis

Functions

Static functions

  • def checkConnectArgs (signal, method)

  • def checkConnectArgs (signal, method)

  • def connectSlotsByName (o)

  • def disconnect (sender, signal_index, receiver, method_index)

  • def disconnectOne (sender, signal_index, receiver, method_index)

  • def invokeMethod (obj, member, arg__3, ret[, val0=QGenericArgument(nullptr)[, val1=QGenericArgument()[, val2=QGenericArgument()[, val3=QGenericArgument()[, val4=QGenericArgument()[, val5=QGenericArgument()[, val6=QGenericArgument()[, val7=QGenericArgument()[, val8=QGenericArgument()[, val9=QGenericArgument()]]]]]]]]]])

  • def invokeMethod (obj, member, ret[, val0=QGenericArgument(nullptr)[, val1=QGenericArgument()[, val2=QGenericArgument()[, val3=QGenericArgument()[, val4=QGenericArgument()[, val5=QGenericArgument()[, val6=QGenericArgument()[, val7=QGenericArgument()[, val8=QGenericArgument()[, val9=QGenericArgument()]]]]]]]]]])

  • def invokeMethod (obj, member, type[, val0=QGenericArgument(nullptr)[, val1=QGenericArgument()[, val2=QGenericArgument()[, val3=QGenericArgument()[, val4=QGenericArgument()[, val5=QGenericArgument()[, val6=QGenericArgument()[, val7=QGenericArgument()[, val8=QGenericArgument()[, val9=QGenericArgument()]]]]]]]]]])

  • def invokeMethod (obj, member[, val0=QGenericArgument(nullptr)[, val1=QGenericArgument()[, val2=QGenericArgument()[, val3=QGenericArgument()[, val4=QGenericArgument()[, val5=QGenericArgument()[, val6=QGenericArgument()[, val7=QGenericArgument()[, val8=QGenericArgument()[, val9=QGenericArgument()]]]]]]]]]])

  • def normalizedSignature (method)

  • def normalizedType (type)

Detailed Description

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:

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() .

See also

QMetaClassInfo QMetaEnum QMetaMethod QMetaProperty QMetaType Meta-Object System

class QMetaObject
PySide2.QtCore.QMetaObject.Call

Constant

Description

QMetaObject.InvokeSlot

QMetaObject.EmitSignal

QMetaObject.ReadProperty

QMetaObject.WriteProperty

QMetaObject.ResetProperty

QMetaObject.QueryPropertyDesignable

QMetaObject.QueryPropertyScriptable

QMetaObject.QueryPropertyStored

QMetaObject.QueryPropertyEditable

QMetaObject.QueryPropertyUser

QMetaObject.CreateInstance
PySide2.QtCore.QMetaObject.cast(obj)
Parameters

obj – QObject

Return type

QObject

Returns obj if object obj inherits from this meta-object; otherwise returns None .

PySide2.QtCore.QMetaObject.cast(obj)
Parameters

obj – QObject

Return type

QObject

Returns obj if object obj inherits from this meta-object; otherwise returns None .

static PySide2.QtCore.QMetaObject.checkConnectArgs(signal, method)
Parameters
Return type

bool

static PySide2.QtCore.QMetaObject.checkConnectArgs(signal, method)
Parameters

  • signal – str

  • method – str

Return type

bool

Returns true if the signal and method arguments are compatible; otherwise returns false .

Both signal and method are expected to be normalized.

See also

normalizedSignature()

PySide2.QtCore.QMetaObject.classInfo(index)
Parameters

index – int

Return type

QMetaClassInfo

Returns the meta-data for the item of class information with the given index .

Example:

class MyClass:

    Q_CLASSINFO("author", "Sabrina Schweinsteiger")
    Q_CLASSINFO("url", "http://doc.moosesoft.co.uk/1.0/")

    ...

See also

classInfoCount() classInfoOffset() indexOfClassInfo()

PySide2.QtCore.QMetaObject.classInfoCount()
Return type

int

Returns the number of items of class information in this class.

See also

classInfo() classInfoOffset() indexOfClassInfo()

PySide2.QtCore.QMetaObject.classInfoOffset()
Return type

int

Returns the class information offset for this class; i.e. the index position of this class’s first class information item.

If the class has no superclasses with class information, the offset is 0; otherwise the offset is the sum of all the class information items in the class’s superclasses.

See also

classInfo() classInfoCount() indexOfClassInfo()

PySide2.QtCore.QMetaObject.className()
Return type

str

Returns the class name.

See also

superClass()

static PySide2.QtCore.QMetaObject.connectSlotsByName(o)
Parameters

o – QObject

Searches recursively for all child objects of the given object , and connects matching signals from them to slots of object that follow the following form:

def on_<object name>_<signal name>(<signal parameters>)

Let’s assume our object has a child object of type QPushButton with the object name button1 . The slot to catch the button’s clicked() signal would be:

def on_button1_clicked()

If object itself has a properly set object name, its own signals are also connected to its respective slots.

See also

setObjectName()

PySide2.QtCore.QMetaObject.constructor(index)
Parameters

index – int

Return type

QMetaMethod

Returns the meta-data for the constructor with the given index .

See also

constructorCount() newInstance()

PySide2.QtCore.QMetaObject.constructorCount()
Return type

int

Returns the number of constructors in this class.

See also

constructor() indexOfConstructor()

static PySide2.QtCore.QMetaObject.disconnect(sender, signal_index, receiver, method_index)
Parameters

  • sender – QObject

  • signal_index – int

  • receiver – QObject

  • method_index – int

Return type

bool

static PySide2.QtCore.QMetaObject.disconnectOne(sender, signal_index, receiver, method_index)
Parameters

  • sender – QObject

  • signal_index – int

  • receiver – QObject

  • method_index – int

Return type

bool

Disconnect a single signal connection. If QMetaObject::connect() has been called multiple times for the same sender, signal_index, receiver and method_index only one of these connections will be removed.

PySide2.QtCore.QMetaObject.enumerator(index)
Parameters

index – int

Return type

QMetaEnum

Returns the meta-data for the enumerator with the given index .

See also

enumeratorCount() enumeratorOffset() indexOfEnumerator()

PySide2.QtCore.QMetaObject.enumeratorCount()
Return type

int

Returns the number of enumerators in this class.

See also

enumerator() enumeratorOffset() indexOfEnumerator()

PySide2.QtCore.QMetaObject.enumeratorOffset()
Return type

int

Returns the enumerator offset for this class; i.e. the index position of this class’s first enumerator.

If the class has no superclasses with enumerators, the offset is 0; otherwise the offset is the sum of all the enumerators in the class’s superclasses.

See also

enumerator() enumeratorCount() indexOfEnumerator()

PySide2.QtCore.QMetaObject.indexOfClassInfo(name)
Parameters

name – str

Return type

int

Finds class information item name and returns its index; otherwise returns -1.

See also

classInfo() classInfoCount() classInfoOffset()

PySide2.QtCore.QMetaObject.indexOfConstructor(constructor)
Parameters

constructor – str

Return type

int

Finds constructor and returns its index; otherwise returns -1.

Note that the constructor has to be in normalized form, as returned by normalizedSignature() .

See also

constructor() constructorCount() normalizedSignature()

PySide2.QtCore.QMetaObject.indexOfEnumerator(name)
Parameters

name – str

Return type

int

Finds enumerator name and returns its index; otherwise returns -1.

See also

enumerator() enumeratorCount() enumeratorOffset()

PySide2.QtCore.QMetaObject.indexOfMethod(method)
Parameters

method – str

Return type

int

Finds method and returns its index; otherwise returns -1.

Note that the method has to be in normalized form, as returned by normalizedSignature() .

See also

method() methodCount() methodOffset() normalizedSignature()

PySide2.QtCore.QMetaObject.indexOfProperty(name)
Parameters

name – str

Return type

int

Finds property name and returns its index; otherwise returns -1.

See also

property() propertyCount() propertyOffset()

PySide2.QtCore.QMetaObject.indexOfSignal(signal)
Parameters

signal – str

Return type

int

Finds signal and returns its index; otherwise returns -1.

This is the same as indexOfMethod() , except that it will return -1 if the method exists but isn’t a signal.

Note that the signal has to be in normalized form, as returned by normalizedSignature() .

See also

indexOfMethod() normalizedSignature() method() methodCount() methodOffset()

PySide2.QtCore.QMetaObject.indexOfSlot(slot)
Parameters

slot – str

Return type

int

Finds slot and returns its index; otherwise returns -1.

This is the same as indexOfMethod() , except that it will return -1 if the method exists but isn’t a slot.

See also

indexOfMethod() method() methodCount() methodOffset()

PySide2.QtCore.QMetaObject.inherits(metaObject)
Parameters

metaObject – QMetaObject

Return type

bool

Returns true if the class described by this QMetaObject inherits the type described by metaObject ; otherwise returns false.

A type is considered to inherit itself.

static PySide2.QtCore.QMetaObject.invokeMethod(obj, member[, val0=QGenericArgument(nullptr)[, val1=QGenericArgument()[, val2=QGenericArgument()[, val3=QGenericArgument()[, val4=QGenericArgument()[, val5=QGenericArgument()[, val6=QGenericArgument()[, val7=QGenericArgument()[, val8=QGenericArgument()[, val9=QGenericArgument()]]]]]]]]]])
Parameters
Return type

bool

This function overloads invokeMethod() .

This overload invokes the member using the connection type AutoConnection and ignores return values.

static PySide2.QtCore.QMetaObject.invokeMethod(obj, member, ret[, val0=QGenericArgument(nullptr)[, val1=QGenericArgument()[, val2=QGenericArgument()[, val3=QGenericArgument()[, val4=QGenericArgument()[, val5=QGenericArgument()[, val6=QGenericArgument()[, val7=QGenericArgument()[, val8=QGenericArgument()[, val9=QGenericArgument()]]]]]]]]]])
Parameters
Return type

bool

This function overloads invokeMethod() .

This overload always invokes the member using the connection type AutoConnection .

static PySide2.QtCore.QMetaObject.invokeMethod(obj, member, arg__3, ret[, val0=QGenericArgument(nullptr)[, val1=QGenericArgument()[, val2=QGenericArgument()[, val3=QGenericArgument()[, val4=QGenericArgument()[, val5=QGenericArgument()[, val6=QGenericArgument()[, val7=QGenericArgument()[, val8=QGenericArgument()[, val9=QGenericArgument()]]]]]]]]]])
Parameters
Return type

bool

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(pushButton, "animateClick",
                         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:

retVal = QString()
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.

See also

Q_ARG() Q_RETURN_ARG() qRegisterMetaType() invoke()

static PySide2.QtCore.QMetaObject.invokeMethod(obj, member, type[, val0=QGenericArgument(nullptr)[, val1=QGenericArgument()[, val2=QGenericArgument()[, val3=QGenericArgument()[, val4=QGenericArgument()[, val5=QGenericArgument()[, val6=QGenericArgument()[, val7=QGenericArgument()[, val8=QGenericArgument()[, val9=QGenericArgument()]]]]]]]]]])
Parameters
Return type

bool

This function overloads invokeMethod() .

This overload can be used if the return value of the member is of no interest.

PySide2.QtCore.QMetaObject.method(index)
Parameters

index – int

Return type

QMetaMethod

Returns the meta-data for the method with the given index .

See also

methodCount() methodOffset() indexOfMethod()

PySide2.QtCore.QMetaObject.methodCount()
Return type

int

Returns the number of methods in this class, including the number of methods provided by each base class. These include signals and slots as well as normal member functions.

Use code like the following to obtain a QStringList containing the methods specific to a given class:

metaObject = obj.metaObject()
methods = [metaObject.method(i).signature() for i in range(metaObject.methodOffset(), metaObject.methodCount())]

See also

method() methodOffset() indexOfMethod()

PySide2.QtCore.QMetaObject.methodOffset()
Return type

int

Returns the method offset for this class; i.e. the index position of this class’s first member function.

The offset is the sum of all the methods in the class’s superclasses (which is always positive since QObject has the deleteLater() slot and a destroyed() signal).

See also

method() methodCount() indexOfMethod()

PySide2.QtCore.QMetaObject.newInstance([val0=QGenericArgument(nullptr)[, val1=QGenericArgument()[, val2=QGenericArgument()[, val3=QGenericArgument()[, val4=QGenericArgument()[, val5=QGenericArgument()[, val6=QGenericArgument()[, val7=QGenericArgument()[, val8=QGenericArgument()[, val9=QGenericArgument()]]]]]]]]]])
Parameters
Return type

QObject

Constructs a new instance of this class. You can pass up to ten arguments (val0 , val1 , val2 , val3 , val4 , val5 , val6 , val7 , val8 , and val9 ) to the constructor. Returns the new object, or 0 if no suitable constructor is available.

Note that only constructors that are declared with the Q_INVOKABLE modifier are made available through the meta-object system.

See also

Q_ARG() constructor()

static PySide2.QtCore.QMetaObject.normalizedSignature(method)
Parameters

method – str

Return type

QByteArray

Normalizes the signature of the given method .

Qt uses normalized signatures to decide whether two given signals and slots are compatible. Normalization reduces whitespace to a minimum, moves ‘const’ to the front where appropriate, removes ‘const’ from value types and replaces const references with values.

See also

checkConnectArgs() normalizedType()

static PySide2.QtCore.QMetaObject.normalizedType(type)
Parameters

type – str

Return type

QByteArray

Normalizes a type .

See normalizedSignature() for a description on how Qt normalizes.

Example:

normType = QMetaObject.normalizedType(" int    const  *")
# normType is now "const int*"

See also

normalizedSignature()

PySide2.QtCore.QMetaObject.property(index)
Parameters

index – int

Return type

QMetaProperty

Returns the meta-data for the property with the given index . If no such property exists, a null QMetaProperty is returned.

See also

propertyCount() propertyOffset() indexOfProperty()

PySide2.QtCore.QMetaObject.propertyCount()
Return type

int

Returns the number of properties in this class, including the number of properties provided by each base class.

Use code like the following to obtain a QStringList containing the properties specific to a given class:

metaObject = obj.metaObject()
properties = [metaObject.property(i).name() for i in range(metaObject.propertyOffset(), metaObject.propertyCount())]

See also

property() propertyOffset() indexOfProperty()

PySide2.QtCore.QMetaObject.propertyOffset()
Return type

int

Returns the property offset for this class; i.e. the index position of this class’s first property.

The offset is the sum of all the properties in the class’s superclasses (which is always positive since QObject has the name() property).

See also

property() propertyCount() indexOfProperty()

PySide2.QtCore.QMetaObject.superClass()
Return type

QMetaObject

Returns the meta-object of the superclass, or 0 if there is no such object.

See also

className()

PySide2.QtCore.QMetaObject.userProperty()
Return type

QMetaProperty

Returns the property that has the USER flag set to true.

See also

isUser()