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Questions tagged [qmetaobject]

QMetaObject is a class from the Qt Toolkit which provides meta-information about Qt objects.

Documentation can be found here (Qt4) and here (Qt5).

61 questions
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Qt - Does a derived class inherit its base class's meta properties?

I am working with Qt and came across class hierarchies where a base class (sometimes an abstract class) contains Q_PROPERTY macros; will a derived class inherit each Q_PROPERTY from its base class?
ethane
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How to go about serializing a large, complex object?

I have a "User" class with 40+ private variables including complex objects like private/public keys (QCA library), custom QObjects etc. The idea is that the class has a function called sign() which encrypts, signs, serializes itself and returns a…
Quoi
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No slots but QMetaObject::connectSlotsByName error using Qt and C++

I'm programming in C++ and Qt Creator and my code works perfectly. Nevertheless I've got the problem that I get a warning when I compile my code. QMetaObject::connectSlotsByName: No matching signal for on_but_PrintTab_clicked() There used to be a…
user3443063
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Qt metaobject system: emit signal using a string with its name

Qt signal/slot system rocks, but looks that it lacks some really useful functionality (or at least I can't find how to use it). I have a class with lots of signals, and this class has a switch which needs to emit a proper signal depending on a…
ScumCoder
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Introspection with QMetaProperty

I have a class ObjectA class ObjectA : public QObject { Q_OBJECT Q_PROPERTY(int _a READ a WRITE setA NOTIFY aChanged) public: ObjectA(int a) : _a(a) {} int a() const { return _a;} public slots: void setA(int a) { _a = a; emit…
artoon
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No matching function to call - compiler says I call (QObject *&) when call is (QObject *)

This is the code: void invokeQMLFunction2Arg(QObject * object, QString func, QVariant p1, QVariant p2) { QMetaObject::invokeMethod(object, func, Qt::DirectConnection, Q_ARG(QVariant, p1), Q_ARG(QVariant, p2)); } This is the error: error: no…
user2341104
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Get object instance class name with Qt's meta-object system

I have 3 classes: class Being : public QObject { Q_OBJECT public: explicit Being(QObject *parent = nullptr); }; class Animal : public Being { Q_OBJECT public: explicit Animal(QObject *parent = nullptr); }; class Dog : public Animal…
Jacob Krieg
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Qt - Compile-time check if qRegisterMetaType() was called

‎ Question: Is there a way to check at compile-time if qRegisterMetaType() was called for a custom type T? The custom type T needs to be registered in Qt meta-type system in order to be used in e.g. queued connections. If such a connection is…
sthlm58
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PySide2 crashes while accessing QObject::property()

So I am not sure this is a bug or something but I have spent quite sometime to figure this out but couldn't. The problem happens when accessing calling QObject::property() function. Here is a minimal reproducible example: import sys from PySide2…
reckless
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How to convert Q_ENUM to QString for QT > 5.11 most efficient way?

I read several advices how to get an actual QString from a Q_ENUM value. Below are 3 possible ways, I came up with, that are compilable constructs in QT5.11.1 What of them should one prefer and why? void…
darkmattercoder
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Is it possible to have a macro function as a QMetaMethod tag?

Qt allows you to have arbitrary tags on slots/Q_INVOKABLE methods using this syntax: // In the class MainWindow declaration #ifndef Q_MOC_RUN // define the tag text as empty, so the compiler doesn't see it # define MY_CUSTOM_TAG #endif ... private…
empyrical
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Qt invokeMethod calling function having output argument

I am trying to figure out the usage of QMetaObject::invokeMethod. I have a function that has one argument(non-const QString), I want it to be the output, the function has no return value, calling invokeMethod on it always fails, while another…
oldnavy
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Adding options to existing Q_PROPERTY from base class only in dereived class

I have a very simple base class which defines a normal Q_PROPERTY with READ and NOTIFY (WRITE is not in all dereived implementations possible). class BaseClass : public QObject { Q_OBJECT Q_PROPERTY(QStringList someEntries READ someEntries…
feedc0de
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Qt4.8: Why enum not seen in qmetaobject? And how to get worked?

Define of "function" I can't refactor. But need use in test class. Used Qt 4.8. The following code return 1, but expected 2. How to use typedef enum in test class? #include #include #include typedef enum { READ …
Andrey Reeshkov
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Enum in Qt property

I have a code, which works with Qt 5.5 and doesn't with Qt 5.2. Problem is with this enum: #include enum Area { Area_A, Area_B, Area_C }; Q_DECLARE_METATYPE(Area) Then I have an object, which exposes this area…
yudjin
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