Qt
Internal/Contributor docs for the Qt SDK. Note: These are NOT official API docs; those are found at https://doc.qt.io/
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\inmodule QtCore More...
#include <qobjectdefs.h>
Classes | |
class | Connection |
\inmodule QtCore Represents a handle to a signal-slot (or signal-functor) connection. More... | |
struct | Data |
struct | SuperData |
Public Types | |
enum | Call { InvokeMetaMethod , ReadProperty , WriteProperty , ResetProperty , CreateInstance , IndexOfMethod , RegisterPropertyMetaType , RegisterMethodArgumentMetaType , BindableProperty , CustomCall , ConstructInPlace } |
Public Member Functions | |
const char * | className () const |
Returns the class name. | |
const QMetaObject * | superClass () const |
Returns the meta-object of the superclass, or \nullptr if there is no such object. | |
bool | inherits (const QMetaObject *metaObject) const noexcept |
Returns true if the class described by this QMetaObject inherits the type described by metaObject; otherwise returns false. | |
QObject * | cast (QObject *obj) const |
const QObject * | cast (const QObject *obj) const |
QString | tr (const char *s, const char *c, int n=-1) const |
QMetaType | metaType () const |
int | methodOffset () const |
Returns the method offset for this class; i.e. | |
int | enumeratorOffset () const |
Returns the enumerator offset for this class; i.e. | |
int | propertyOffset () const |
Returns the property offset for this class; i.e. | |
int | classInfoOffset () const |
Returns the class information offset for this class; i.e. | |
int | constructorCount () const |
int | methodCount () const |
Returns the number of methods in this class, including the number of methods provided by each base class. | |
int | enumeratorCount () const |
Returns the number of enumerators in this class. | |
int | propertyCount () const |
Returns the number of properties in this class, including the number of properties provided by each base class. | |
int | classInfoCount () const |
Returns the number of items of class information in this class. | |
int | indexOfConstructor (const char *constructor) const |
int | indexOfMethod (const char *method) const |
Finds method and returns its index; otherwise returns -1. | |
int | indexOfSignal (const char *signal) const |
Finds signal and returns its index; otherwise returns -1. | |
int | indexOfSlot (const char *slot) const |
Finds slot and returns its index; otherwise returns -1. | |
int | indexOfEnumerator (const char *name) const |
Finds enumerator name and returns its index; otherwise returns -1. | |
int | indexOfProperty (const char *name) const |
Finds property name and returns its index; otherwise returns -1. | |
int | indexOfClassInfo (const char *name) const |
Finds class information item name and returns its index; otherwise returns -1. | |
QMetaMethod | constructor (int index) const |
QMetaMethod | method (int index) const |
Returns the meta-data for the method with the given index. | |
QMetaEnum | enumerator (int index) const |
Returns the meta-data for the enumerator with the given index. | |
QMetaProperty | property (int index) const |
Returns the meta-data for the property with the given index. | |
QMetaClassInfo | classInfo (int index) const |
Returns the meta-data for the item of class information with the given index. | |
QMetaProperty | userProperty () const |
template<typename... Args> | |
QtPrivate::Invoke::IfNotOldStyleArgs< QObject *, Args... > | newInstance (Args &&... arguments) const |
int | static_metacall (Call, int, void **) const |
Static Public Member Functions | |
static bool | checkConnectArgs (const char *signal, const char *method) |
Returns true if the signal and method arguments are compatible; otherwise returns false . | |
static bool | checkConnectArgs (const QMetaMethod &signal, const QMetaMethod &method) |
static QByteArray | normalizedSignature (const char *method) |
Normalizes the signature of the given method. | |
static QByteArray | normalizedType (const char *type) |
static Connection | connect (const QObject *sender, int signal_index, const QObject *receiver, int method_index, int type=0, int *types=nullptr) |
static bool | disconnect (const QObject *sender, int signal_index, const QObject *receiver, int method_index) |
static bool | disconnectOne (const QObject *sender, int signal_index, const QObject *receiver, int method_index) |
static void | connectSlotsByName (QObject *o) |
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: | |
static void | activate (QObject *sender, int signal_index, void **argv) |
static void | activate (QObject *sender, const QMetaObject *, int local_signal_index, void **argv) |
static void | activate (QObject *sender, int signal_offset, int local_signal_index, void **argv) |
static bool | invokeMethod (QObject *obj, const char *member, Qt::ConnectionType, QGenericReturnArgument ret, QGenericArgument val0=QGenericArgument(nullptr), QGenericArgument val1=QGenericArgument(), QGenericArgument val2=QGenericArgument(), QGenericArgument val3=QGenericArgument(), QGenericArgument val4=QGenericArgument(), QGenericArgument val5=QGenericArgument(), QGenericArgument val6=QGenericArgument(), QGenericArgument val7=QGenericArgument(), QGenericArgument val8=QGenericArgument(), QGenericArgument val9=QGenericArgument()) |
\threadsafe This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. \obsolete [6.5] Please use the variadic overload of this function | |
static bool | invokeMethod (QObject *obj, const char *member, QGenericReturnArgument ret, QGenericArgument val0=QGenericArgument(nullptr), QGenericArgument val1=QGenericArgument(), QGenericArgument val2=QGenericArgument(), QGenericArgument val3=QGenericArgument(), QGenericArgument val4=QGenericArgument(), QGenericArgument val5=QGenericArgument(), QGenericArgument val6=QGenericArgument(), QGenericArgument val7=QGenericArgument(), QGenericArgument val8=QGenericArgument(), QGenericArgument val9=QGenericArgument()) |
static bool | invokeMethod (QObject *obj, const char *member, Qt::ConnectionType type, QGenericArgument val0, QGenericArgument val1=QGenericArgument(), QGenericArgument val2=QGenericArgument(), QGenericArgument val3=QGenericArgument(), QGenericArgument val4=QGenericArgument(), QGenericArgument val5=QGenericArgument(), QGenericArgument val6=QGenericArgument(), QGenericArgument val7=QGenericArgument(), QGenericArgument val8=QGenericArgument(), QGenericArgument val9=QGenericArgument()) |
static bool | invokeMethod (QObject *obj, const char *member, QGenericArgument val0, QGenericArgument val1=QGenericArgument(), QGenericArgument val2=QGenericArgument(), QGenericArgument val3=QGenericArgument(), QGenericArgument val4=QGenericArgument(), QGenericArgument val5=QGenericArgument(), QGenericArgument val6=QGenericArgument(), QGenericArgument val7=QGenericArgument(), QGenericArgument val8=QGenericArgument(), QGenericArgument val9=QGenericArgument()) |
template<typename ReturnArg , typename... Args> | |
static QtPrivate::Invoke::IfNotOldStyleArgs< bool, Args... > | invokeMethod (QObject *obj, const char *member, Qt::ConnectionType c, QTemplatedMetaMethodReturnArgument< ReturnArg > r, Args &&... arguments) |
template<typename... Args> | |
static QtPrivate::Invoke::IfNotOldStyleArgs< bool, Args... > | invokeMethod (QObject *obj, const char *member, Qt::ConnectionType c, Args &&... arguments) |
template<typename ReturnArg , typename... Args> | |
static QtPrivate::Invoke::IfNotOldStyleArgs< bool, Args... > | invokeMethod (QObject *obj, const char *member, QTemplatedMetaMethodReturnArgument< ReturnArg > r, Args &&... arguments) |
template<typename... Args> | |
static QtPrivate::Invoke::IfNotOldStyleArgs< bool, Args... > | invokeMethod (QObject *obj, const char *member, Args &&... arguments) |
template<typename Func > | |
static std::enable_if_t<!std::disjunction_v< std::is_convertible< Func, const char * >, QtPrivate::Invoke::AreOldStyleArgs< Func > >, bool > | invokeMethod (typename QtPrivate::ContextTypeForFunctor< Func >::ContextType *object, Func &&function, Qt::ConnectionType type, typename QtPrivate::Callable< Func >::ReturnType *ret) |
template<typename Func > | |
static std::enable_if_t<!std::disjunction_v< std::is_convertible< Func, const char * >, QtPrivate::Invoke::AreOldStyleArgs< Func > >, bool > | invokeMethod (typename QtPrivate::ContextTypeForFunctor< Func >::ContextType *object, Func &&function, typename QtPrivate::Callable< Func >::ReturnType *ret) |
template<typename Func , typename... Args> | |
static std::enable_if_t<!std::disjunction_v< std::is_convertible< Func, const char * >, QtPrivate::Invoke::AreOldStyleArgs< Args... > >, bool > | invokeMethod (typename QtPrivate::ContextTypeForFunctor< Func >::ContextType *object, Func &&function, Qt::ConnectionType type, QTemplatedMetaMethodReturnArgument< typename QtPrivate::Callable< Func, Args... >::ReturnType > ret, Args &&...args) |
template<typename Func , typename... Args> | |
static std::enable_if_t<!std::disjunction_v< std::is_convertible< Func, const char * >, QtPrivate::Invoke::AreOldStyleArgs< Args... > >, bool > | invokeMethod (typename QtPrivate::ContextTypeForFunctor< Func >::ContextType *object, Func &&function, Qt::ConnectionType type, Args &&...args) |
template<typename Func , typename... Args> | |
static std::enable_if_t<!std::disjunction_v< std::is_convertible< Func, const char * >, QtPrivate::Invoke::AreOldStyleArgs< Args... > >, bool > | invokeMethod (typename QtPrivate::ContextTypeForFunctor< Func >::ContextType *object, Func &&function, QTemplatedMetaMethodReturnArgument< typename QtPrivate::Callable< Func, Args... >::ReturnType > ret, Args &&...args) |
template<typename Func , typename... Args> | |
static std::enable_if_t<!std::disjunction_v< std::is_convertible< Func, const char * >, QtPrivate::Invoke::AreOldStyleArgs< Args... > >, bool > | invokeMethod (typename QtPrivate::ContextTypeForFunctor< Func >::ContextType *object, Func &&function, Args &&...args) |
static int | metacall (QObject *, Call, int, void **) |
template<const QMetaObject & MO> | |
static constexpr const QMetaObject * | staticMetaObject () |
Public Attributes | |
struct QMetaObject::Data | d |
Friends | |
class | QTimer |
class | QChronoTimer |
\inmodule QtCore
The QMetaObject class contains meta-information about Qt objects.
The Qt \l{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 QObject::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: \list
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().
Definition at line 237 of file qobjectdefs.h.
enum QMetaObject::Call |
\value InvokeMetaMethod \value ReadProperty \value WriteProperty \value ResetProperty \value CreateInstance \value IndexOfMethod \value RegisterPropertyMetaType \value RegisterMethodArgumentMetaType \value BindableProperty \value CustomCall \value ConstructInPlace
Enumerator | |
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InvokeMetaMethod | |
ReadProperty | |
WriteProperty | |
ResetProperty | |
CreateInstance | |
IndexOfMethod | |
RegisterPropertyMetaType | |
RegisterMethodArgumentMetaType | |
BindableProperty | |
CustomCall | |
ConstructInPlace |
Definition at line 548 of file qobjectdefs.h.
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Definition at line 4179 of file qobject.cpp.
signal_index comes from indexOfMethod()
Definition at line 4207 of file qobject.cpp.
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Definition at line 4193 of file qobject.cpp.
Returns obj if object obj inherits from this meta-object; otherwise returns \nullptr.
Definition at line 406 of file qmetaobject.cpp.
Returns obj if object obj inherits from this meta-object; otherwise returns \nullptr.
Definition at line 244 of file qobjectdefs.h.
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Returns true
if the signal and method arguments are compatible; otherwise returns false
.
Both signal and method are expected to be normalized.
Definition at line 1280 of file qmetaobject.cpp.
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Returns true
if the signal and method arguments are compatible; otherwise returns false
.
Definition at line 1302 of file qmetaobject.cpp.
QMetaClassInfo QMetaObject::classInfo | ( | int | index | ) | const |
Returns the meta-data for the item of class information with the given index.
Example:
Definition at line 1257 of file qmetaobject.cpp.
int QMetaObject::classInfoCount | ( | ) | const |
Returns the number of items of class information in this class.
Definition at line 632 of file qmetaobject.cpp.
int QMetaObject::classInfoOffset | ( | ) | const |
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.
Definition at line 542 of file qmetaobject.cpp.
const char * QMetaObject::className | ( | ) | const |
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types is a 0-terminated vector of meta types for queued connections.
if signal_index is -1, then we effectively connect all signals from the sender to the receiver's slot
Definition at line 3570 of file qobject.cpp.
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:
Let's assume our object has a child object of type {QPushButton} with the \l{QObject::objectName}{object name}
{button1}. The slot to catch the button's
{clicked()} signal would be:
If object itself has a properly set object name, its own signals are also connected to its respective slots.
Definition at line 3821 of file qobject.cpp.
QMetaMethod QMetaObject::constructor | ( | int | index | ) | const |
Returns the meta-data for the constructor with the given index.
Definition at line 1169 of file qmetaobject.cpp.
int QMetaObject::constructorCount | ( | ) | const |
Returns the number of constructors in this class.
Definition at line 560 of file qmetaobject.cpp.
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Definition at line 3655 of file qobject.cpp.
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\internal
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.
Definition at line 3671 of file qobject.cpp.
QMetaEnum QMetaObject::enumerator | ( | int | index | ) | const |
Returns the meta-data for the enumerator with the given index.
Definition at line 1199 of file qmetaobject.cpp.
int QMetaObject::enumeratorCount | ( | ) | const |
Returns the number of enumerators in this class.
Definition at line 594 of file qmetaobject.cpp.
int QMetaObject::enumeratorOffset | ( | ) | const |
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.
Definition at line 500 of file qmetaobject.cpp.
int QMetaObject::indexOfClassInfo | ( | const char * | name | ) | const |
Finds class information item name and returns its index; otherwise returns -1.
Definition at line 1147 of file qmetaobject.cpp.
int QMetaObject::indexOfConstructor | ( | const char * | constructor | ) | const |
Finds constructor and returns its index; otherwise returns -1.
Note that the constructor has to be in normalized form, as returned by normalizedSignature().
Definition at line 737 of file qmetaobject.cpp.
int QMetaObject::indexOfEnumerator | ( | const char * | name | ) | const |
Finds enumerator name and returns its index; otherwise returns -1.
Definition at line 1076 of file qmetaobject.cpp.
int QMetaObject::indexOfMethod | ( | const char * | method | ) | const |
Finds method and returns its index; otherwise returns -1.
Note that the method has to be in normalized form, as returned by normalizedSignature().
Definition at line 753 of file qmetaobject.cpp.
int QMetaObject::indexOfProperty | ( | const char * | name | ) | const |
Finds property name and returns its index; otherwise returns -1.
Definition at line 1115 of file qmetaobject.cpp.
int QMetaObject::indexOfSignal | ( | const char * | signal | ) | const |
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().
Definition at line 818 of file qmetaobject.cpp.
int QMetaObject::indexOfSlot | ( | const char * | slot | ) | const |
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.
Definition at line 865 of file qmetaobject.cpp.
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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.
Definition at line 382 of file qmetaobject.cpp.
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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.
For the overloads with a QTemplatedMetaMethodReturnArgument parameter, the return value of the member function call is placed in ret. For the overloads without such a member, the return value of the called function (if any) will be discarded. QTemplatedMetaMethodReturnArgument is an internal type you should not use directly. Instead, use the qReturnArg() function.
The overloads with a Qt::ConnectionType type parameter allow explicitly selecting whether the invocation will be synchronous or not:
\list
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 \l{QThread::quit()}{quit()} slot on a QThread, use the following code:
With asynchronous method invocations, the parameters must be copyable types, because Qt needs to copy the arguments to store them in an event behind the scenes. Since Qt 6.5, this function automatically registers the types being used; however, as a side-effect, it is not possible to make calls using types that are only forward-declared. Additionally, it is not possible to make asynchronous calls that use references to non-const-qualified types as parameters either.
To synchronously invoke the compute(QString, int, double)
slot on some arbitrary object obj
retrieve its return value:
If the "compute" slot does not take exactly one \l QString, one int
, and one double
in the specified order, the call will fail. Note how it was necessary to be explicit about the type of the QString, as the character literal is not exactly the right type to match. If the method instead took a \l QStringView, a \l qsizetype, and a float
, the call would need to be written as:
The same call can be executed using the Q_ARG() and Q_RETURN_ARG() macros, as in:
The macros are kept for compatibility with Qt 6.4 and earlier versions, and can be freely mixed with parameters that do not use the macro. They may be necessary in rare situations when calling a method that used a typedef to forward-declared type as a parameter or the return type.
Definition at line 414 of file qobjectdefs.h.
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Definition at line 353 of file qobjectdefs.h.
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Definition at line 319 of file qobjectdefs.h.
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Definition at line 390 of file qobjectdefs.h.
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Definition at line 376 of file qobjectdefs.h.
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Definition at line 336 of file qobjectdefs.h.
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\threadsafe This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts. \obsolete [6.5] Please use the variadic overload of this function
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.
See the variadic invokeMethod() function for more information. This function should behave the same way as that one, with the following limitations:
\list
With asynchronous method invocations, the parameters must be of types that are already 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
call qRegisterMetaType() to register the data type before you call invokeMethod().
Definition at line 1558 of file qmetaobject.cpp.
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Definition at line 402 of file qobjectdefs.h.
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Definition at line 510 of file qobjectdefs.h.
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Definition at line 481 of file qobjectdefs.h.
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Definition at line 466 of file qobjectdefs.h.
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Definition at line 439 of file qobjectdefs.h.
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Definition at line 495 of file qobjectdefs.h.
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Definition at line 456 of file qobjectdefs.h.
Definition at line 342 of file qmetaobject.cpp.
QMetaType QMetaObject::metaType | ( | ) | const |
Definition at line 426 of file qmetaobject.cpp.
QMetaMethod QMetaObject::method | ( | int | index | ) | const |
Returns the meta-data for the method with the given index.
Definition at line 1182 of file qmetaobject.cpp.
int QMetaObject::methodCount | ( | ) | const |
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:
Definition at line 578 of file qmetaobject.cpp.
int QMetaObject::methodOffset | ( | ) | const |
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).
Definition at line 478 of file qmetaobject.cpp.
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Constructs a new instance of this class and returns the new object, or \nullptr if no suitable constructor is available. The types of the arguments arguments will be used to find a matching constructor, and then forwarded to it the same way signal-slot connections do.
Note that only constructors that are declared with the Q_INVOKABLE modifier are made available through the meta-object system.
Definition at line 541 of file qobjectdefs.h.
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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.
Definition at line 1378 of file qmetaobject.cpp.
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Normalizes a type.
See QMetaObject::normalizedSignature() for a description on how Qt normalizes.
Example:
Definition at line 1362 of file qmetaobject.cpp.
QMetaProperty QMetaObject::property | ( | int | index | ) | const |
Returns the meta-data for the property with the given index.
If no such property exists, a null QMetaProperty is returned.
Definition at line 1217 of file qmetaobject.cpp.
int QMetaObject::propertyCount | ( | ) | const |
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:
Definition at line 616 of file qmetaobject.cpp.
int QMetaObject::propertyOffset | ( | ) | const |
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).
Definition at line 521 of file qmetaobject.cpp.
Definition at line 330 of file qmetaobject.cpp.
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Definition at line 565 of file qobjectdefs.h.
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Returns the meta-object of the superclass, or \nullptr if there is no such object.
Definition at line 680 of file qobjectdefs.h.
QString QMetaObject::tr | ( | const char * | s, |
const char * | c, | ||
int | n = -1 ) const |
Definition at line 415 of file qmetaobject.cpp.
QMetaProperty QMetaObject::userProperty | ( | ) | const |
Returns the property that has the USER
flag set to true.
Definition at line 1236 of file qmetaobject.cpp.
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Definition at line 646 of file qobjectdefs.h.
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Definition at line 645 of file qobjectdefs.h.
struct QMetaObject::Data QMetaObject::d |