Apr 24, 2018 I'm having a problem with QT regarding multiple enheritance because of QObject. I know that a lot of others have the same problems but I don't know how I should fix it. Qt multiple inheritance and signals. QObject::connect not connecting signal to slot. Qt “signal undefined reference error” after inheriting from QObject. 94 answers level 19 poker. Type-safe Signals and Slots in C: Part 2. Boost and QT also offer signal / slot functionality (see Part 1 of the article series). However, the signal slot system by ElmueSoft described in this article has the great advantage that it is tiny, does not need any big libraries or compiler plugins and it is free. Qt/C - Lesson 018. QGraphicsItem – The inheritance and slots. Let's talk a little about the inheritance from QGraphicsItem and application of signals and slots system in interaction with graphical objects on the graphic scene QGra. For a detailed article on multiple inheritance, see this Wikipedia entry. Use of Multiple Inheritance of Qt. By my count, there are 17 public classes in Qt 5.0.1 that make use of multiple inheritance. Here is the complete list (by the way, we just answered trivia questions 1 and 2): QAxObject inherits QObject and QAxBase.
I need to use multiple inheritance because I need to (1) implement an 'is-a' relationship from QGraphicsItem, and (2) implement an application-specific interface (MyInterface):
New online casinos for us players. You may not have access to every casino game that computer users do, but you will be able to perform most functions on your phone, including making deposits and withdrawals. Almost all modern devices are compatible to play these games, so whether you own an iPhone, iPad, Android or even Windows Phone, you will be able to play your favorite casino games straight from your.Most often you can, these are called instant play casinos. An important point to remember about online casinos is that most do not design their own proprietary software, but instead pay for software support from one or more developers. In some cases, USA online casinos will offer the option to on your computer or an app. These days everyone has a mobile device of some kind, so it’s no surprise that online casino sites are that can be played on a phone or tablet.
@class MyClass : public QGraphicsTextItem, public MyInterface@
I would like to connect to signals from pointers to the interface, i.e.:
@MyInterface *my_interface_instance = GetInstance();
connect(my_interface_instance, SIGNAL(MyInterfaceSignal()), this, SLOT(SomeSlot()));@
connect(my_interface_instance, SIGNAL(MyInterfaceSignal()), this, SLOT(SomeSlot()));@
Problem: To expose signals in MyInterface, it needs to derive from QObject. But then I have multiple-inheritance from QObject, which is not allowed. The solutions on 'this article':http://doc.trolltech.com/qq/qq15-academic.html are IMO fairly useless in the common case (accessing an object through its interface), because you cannot connect the signals and slots from MyInterface* but must cast it to the derived-type. Since MyClass is one of many MyInterface-derived classes, this would necessitate 'code-smelly' if-this-cast-to-this-else-if-that-cast-to-that statements and defeats the purpose of the interface.
The solution below seems to work, but I was hoping a Troll could let me know if this is supported or is going to cause undefined behavior. If I dynamic_cast a MyInterface* to QObject* (because I know all MyInterface-derived classes also inherit eventually from QObject), it seems to work:
@class MyInterface {
protected:
virtual void MyInterfaceSignal() = 0;
};
protected:
virtual void MyInterfaceSignal() = 0;
};
Star trek slots facebook. An all-time play. Actually, it was styled to fit the context of a famous Star Trek scenes. Star Trek: Red Alert Free Online Slot Machine ReviewWatch all episodes of Star Trek play unfold in a 25 fixed play line winning ways offered by a 3-rowed format slot. The episodes come disguised with aliens sparks, celebrities, shield, medals, and ammunition.Play Star Trek: Red Alert free online as you watch scenes themed in a myriad of star colors one after the other.
class MyClass : public QGraphicsTextItem, public MyInterface {
Q_OBJECT
signals:
void MyInterfaceSignal();
};
@
Q_OBJECT
signals:
void MyInterfaceSignal();
};
@
Usage:
@MyInterface my_interface_instance = GetInstance();
connect(dynamic_cast<QObject>(my_interface_instance), SIGNAL(MyInterfaceSignal()), this, SLOT(SomeSlot()));@
connect(dynamic_cast<QObject>(my_interface_instance), SIGNAL(MyInterfaceSignal()), this, SLOT(SomeSlot()));@
Qt Signal Slots
Is this a bad idea?
Overriding/Reimplementing Slots in PySide
python,qt,override,pyside,signals-slots
You cannot override QLineEdit.copy or QLineEdit.paste in such a way that they will be called internally by Qt. In general, you can only usefully override or reimplement Qt functions that are defined as being virtual. The Qt Docs will always specify whether this is the case, and for QLineEdit, there..
C++ Signal QML Slot on registered type
c++,qml,signals-slots,qt5.4
I hadn't realized that I had connected to the wrong instance of MsgController in my code. One instance was created by the C++ code, but I really wanted to call the slot on the instance created by the Qml Engine. Once I connected to the correct instance, the code above..
connecting signals and slots with different relations
c++,qt,connect,signals-slots
Duty Roulette: Level 50/60/70. Duty Roulette: Level 50/60/70 will put the player into a random level 50, level 60, or level 70 light party dungeon. As of patch 4.0, access to this Duty Roulette requires unlocking a minimum of 2 of the included dungeons. Players must also have an average item level of 90 or greater. Ffxiv duty roulette high level. Duty roulette is an activity that can be undertaken daily for rewards of Allagan Tomestones, Gil, and Grand Company Seals.Upon reaching the necessary level, a player may select a particular Duty Roulette section and be matched into an appropriate instance.
You need to create new slot for that purpose. But in C++ 11 and Qt 5 style you can use labmdas! It is very comfortable for such short functions. In your case: connect(ui->horizontalSlider, &QSlider::sliderMoved, this, [this](int x) { this->ui->progressBar->setValue(x / 2); }); ..
How to connect signal to boost::asio::io_service when posting work on different thread?
c++,multithreading,boost,boost-asio,signals-slots
In light of new information, the problem is with your boost::bind. You are trying to call a member function without an object to call it on: you are trying to call ProcessData but you haven't told the bind on which object you wish to call it on. You need to..
PyQt5: one signal comes instead of two as per documentation
python,pyqt,python-3.3,signals-slots,pyqt5
![Signal Signal](/uploads/1/2/5/2/125255595/191501363.jpg)
You only connected to one of the two signal overloads. Since you also didn't specify which overload you wanted, a default will be selected - which in this case will be valueChanged(int). To explicitly select both overloads, you would need to do: self.spb.valueChanged[int].connect(self.onValueChanged) self.spb.valueChanged[str].connect(self.onValueChanged) .. def onValueChanged(self, x): print('QSpinBox: value..
Set value using signal is not behaving as expected in Qt
c++,qt,signals-slots,qthread,qwebview
My suspect is that you are stopping the event loop of the thread doing the sleep. Threads in Qt are a bit tricky. Take a look at this, it makes all these questions very clear. I'd say you should use the Element when you are sure you got it and..
Qt app receives HUP signal unexpectedly when forked to background
qt,signals,fork,daemon,signals-slots
When daemonizing (forking), the parent process issues a HUP signal upon exit. For some reason on Red Hat this signal doesn't hit child process until much later. On Ubuntu the signal hits the child quickly (or perhaps Ubuntu holds the signal for the child). Solution is to confirm parent process..
Qt signal argument thread safety
c++,multithreading,qt,signals-slots
Thankfully, Qt protects you from yourself and will copy the image so that you don't shoot yourself in the foot. The copying will be done upon signal's emission, and is done from inside of the implementation of the signal - here, the copying is done when Object::source is on the..
qt slots and signalls autoconnecting
qt,qt5,signals-slots,qt5.2
I fixed it by accident while writing this question.. My model was missing a name. When I added kontrahentModel->setObjectName('kontrahentModel'); All worked like a charm.. BUT - 'there is no rose without a thorn'. When assigning a parent for the model, an old problem returns - described here: QSqlQueryModel with a..
qt 'emit' signal not working properly
c++,qt,signals-slots,emit
Remove the multiple instances of dosecalibration, or make sure to connect each one of those, if you really need multiple instances.
How to keep track of signals and slots in Qt?
qt,signals-slots
Conan is a C++ library that provides run-time introspection of object hierarchies, object inheritance, signal/slot connections, and signal emissions. GammaRay is another advanced analyser which can show signals/slots..
Qt - Connect slot with argument using lambda
python,qt,lambda,pyqt,signals-slots
The issue is python's scoping rules & closures. You need to capture the group: def connections(self): for group in self.widgets: self.widgets[group].clicked.connect(lambda g=group: self.openMenu(g)) def openMenu(self,group): print group ..
Syntax sugar for signal slot
c++,c++11,signals-slots
Is it possible in modern C++ to implement such functionality in, for example, C# way? [..] No, that's not possible in C++. The syntax for taking the address of a member function requires qualifying the function name with the class name (i.e. &MyClassName::myMethodName). If you don't want to specify..
QSocketNotifier signal has a different signature than the assigned slot
qt,signals-slots
From the Qt docs: The signature of a signal must match the signature of the receiving slot. (In fact a slot may have a shorter signature than the signal it receives because it can ignore extra arguments.).. So, in your case it should also work because the slot has less..
QDialogButtonBox buttons not responding
c++,qt,signals-slots,qt-designer,qdialog
You are specifying the wrong receiver in the connection. It's the dialog that has the accept() and reject() slots, not the main window (i.e. this). So, instead, you just need: connect(buttonBox, SIGNAL(accepted()), &dlg, SLOT(accept())); connect(buttonBox, SIGNAL(rejected()), &dlg, SLOT(reject())); And now when you click the buttons, the dialog will close, and..
Cross-thread signal slot, how to send char *
c++,multithreading,qt,signals-slots
The problem you have is completely unrelated to Qt, signals or multiple threads. The char* you're creating isn't null-terminated, so you cannot use it with functions (or operators) that expect char*s to be C strings - they rely on the null terminator. What you're seeing on your console is the..
Cannot connect (null)::selectionChanged to QTableView
c++,qt,qt-creator,signals-slots,qtableview
The signal slot connection has failed since table->selectionModel() has returned null. If you set the model for your table before making signal slot connection, table->selectionModel() will return a valid model, making the signal slot connection successful..
Communication with QThread not working with Signals / Slots
c++,qt,signals-slots,qthread,qobject
Thanks for the input. I solved it by having a singleton that has a flag that the processing loop in my worker object in the QThread reads each loop iteration. It is protected by a QReadWrite lock. int UdpThreadController::killUdpThread(int frameType) { #if SINGLETON_CAMERA_UDP_DEBUG qDebug() << 'Killing Thread! Frame type is:..
PyQt4 signals and slots - QToolButton
python,qt,pyqt4,signals-slots
I'm not sure why you're doing the following, but that's the issue: def showSettings(self): dialog = QtGui.QDialog() dialog.ui = SettingsDialog() dialog.ui.setupUi(dialog) dialog.exec_() SettingsDialog itself is a proper QDialog. You don't need to instantiate another QDialog. Right now, you're creating an empty QDialog and then populate it with the same ui..
Dynamic mapping of all QT signals of one object to one slot
c++,qt,signals-slots
have a look at const char * QMetaMethod::signature() const then you should be able to use it like QObject::connect(object, method->signature(), this, SLOT(signalFired())); you might need to add '2' before the method->signature() call because SIGNAL(a) makro is defined SIGNAL(a) '2'#a as mentioned Is it possible to see definition of Q_SIGNALS, Q_SLOT,..
PyQt: Wrapping Dialog from QDesigner and Connect pushbutton
python,pyqt,signals-slots,qpushbutton,pyuic
The problem in the original code is in this section: if True: qApp = QtGui.QApplication(sys.argv) Dialog = QtGui.QDialog() u = Testdialog() u.setupUi(Dialog) Dialog.exec_() sys.exit(qApp.exec_()) What you want instead is something like this: if __name__ '__main__': app = QtGui.QApplication(sys.argv) u = Testdialog() u.show() sys.exit(app.exec_()) The reason why the original code..
PyQt5 - Signals&Slots - How to enable a button through content change of lineEdit?
button,signals-slots,pyqt5,qlineedit
Looks like you want the textChanged signal, since that sends the current text: self.lineEdit_SelectedDirectory.textChanged.connect( lambda text: self.pushButton_CreateFileList.setEnabled(bool(text))) ..
Qt/C++ how to wait a slot when signal emitted
c++,multithreading,qt5,signals-slots
My first thought is that having either thread block until an operation in the other thread completes is a poor design -- it partially defeats the purpose of having multiple threads, which is to allow multiple operations to run in parallel. It's also liable to result in deadlocks if you're..
How to resolve 2 sequential calls on Qt slot and perform action only once
c++,qt,lambda,signals-slots,qt-signals
You can apply next pattern to your code: class MyClass : public QObject { private slots: void updateRequest(); private: QTimer *_timer; CodeEditor *_editor; }; MyClass::MyClass() { // Init members // .. _timer->setSingleShot( true ); _timer->setInterval( 0 ); connect( _editor, &CodeEditor:: cursorPositionChanged, _timer, &QTimer::start); connect( _editor, &CodeEditor:: selectionChanged, _timer, &QTimer::start); connect(..
How to connect an abstract signal to a slot within the interface's constructor?
c++,qt,inheritance,multiple-inheritance,signals-slots
Generally speaking, interfaces should be abstract classes, and their constructors shouldn't be doing anything at all. So this is bad design. If you insist on doing things such way, the semantics of C++ prevents us from doing it exactly as you state. When you multiply-inherit, a dynamic_cast to C will..
Qt Connecting Signal to Slots
c++,qt,signals-slots
You can't use arguments in connect, only types. So try next: QObject::connect(classA.get(), SIGNAL(posChanged(int, int)), this, SLOT(posChanged(int, int))); ..
Qt:signal slot pass by const reference
c++,qt,pass-by-reference,signals-slots,pass-by-value
When you pass an argument by reference, a copy would be sent in a queued connection. Indeed the arguments are always copied when you have a queued connection. So here there would be no trouble regarding the life time of images since it will be copied instead of passed by..
PyQt: ListWidget.insertItem not shown
python,pyqt,signals-slots,qt-designer,qlistwidget
There is only one button in your dialog, and so it will become the auto-default. This means that whenever you press enter in the dialog, the button will receive a press event, even if it doesn't currently have the keyboard focus. So the item does get added to the list-widget..
Send signal with boolean argument
python,python-2.7,pyside,signals-slots
This is easy if you read the documentation from PySide import QtCore class A(QtCore.QObject): status = QtCore.Signal(bool) def func1(self, *args): self.status.emit(*args) # later.. @QtCore.Slot(bool) def update(self, bool_args): pass # insert what you need to do here. ..
Can't emit signal in QML custom Item
qt,qml,signals-slots
Functions (which signals are) are first class objects in JS, so it is not an error to refer to them without parentheses. But you need them in order to execute the function (i.e. emit the signal). So just change this line: onClicked: baseButton.clicked() ..
Event loops and signal-slot processing when using multithreading in Qt
c++,multithreading,qt,event-loop,signals-slots
All results you got are perfectly correct. I'll try to explain how this works. An event loop is an internal loop in Qt code that processes system and user events. Event loop of main thread is started when you call a.exec(). Event loop of another thread is started by default..
Qt slot connected successful but wasn't fired
qt,signals-slots,qtcpserver
I'm not quite sure what you're doing wrong try adding public in the inheritance line (: public QObject). The following code works for me: server.hpp #ifndef _SERVER_HPP_ #define _SERVER_HPP_ #include <QtNetwork> class Server : public QObject { Q_OBJECT public: Server(); private slots: void handleClient(); private: QTcpServer* mServer; }; #endif server.cpp..
Is there a way to check duplicated connection in Qt?
c++,qt,duplicates,signals-slots
You can use Conan which is a connection analyzer for Qt. Using it you can see object hierarchies, object inheritance, signal/slot connections, and signal emissions at run time. It claims that : Conan has been used to identify multiple duplicate connections in the source code of Qt! An other option..
How to execute a function in Qt when a variable changes its value in the QML?
c++,qt,signals,signals-slots
Using your example regarding ints, it would be done like this: class foo : public QObject { Q_OBJECT Q_PROPERTY( int value READ getValue WRITE setValue NOTIFY valueChanged ) public: explicit foo( QObject* parent = nullptr ) : QObject{ parent }, i_{ 0 } {} virtual ~foo() {} int getValue() const..
How can I be notified by QItemSelectionModel when no items are selected?
qt,pyqt,qt5,signals-slots,pyqt5
Turns out to not be quite true that QItemSelectionModel.selectionChanged doesn't get emitted when items are deselected, at least that's how it currently works for me. In fact, I receive this signal with an empty QItemSelection for the indexes argument.
Disconnecting signals fails
c++,qt,signals-slots
I've checked how QObject::disconnect is implemented and I don't see how this is supposed to work if you only specify receiver. QMetaObjectPrivate::disconnect will return immediately with false when sender is not specified. This means that second part of QObject::disconnect will no set res to true. The only other place you..
Attempting to read stdout from spawned QProcess
qt,signals-slots,qprocess
Issue is in statement QObject::connect(console_backend, SIGNAL(console_backend ->readyReadStandardOutput()), this, SLOT(this->receiveConsoleBackendOutput())); It should be QObject::connect(console_backend, SIGNAL(readyReadStandardOutput()), this, SLOT(receiveConsoleBackendOutput())); ..
How to close Pyqt5 program from QML?
qt,python-3.x,qml,signals-slots,pyqt5
There are a few syntax errors in the python script, but ignoring those, the code can be made to work like this: def main(argv): app = DestinyManager(sys.argv) engine = QtQml.QQmlEngine(app) engine.quit.connect(app.quit) .. Which is to say, you simply need to connect the qml quit signal to an appropriate slot in..
Qt proper connect() calling
c++,qt,signals-slots
I presume, your exit_button_clicked() is declared as a private or public function (not as a slot). Qt custom signals and slots have to be declared in a proper way. For example, you have your class Tutorial: class Tutorial : QWidget { Q_OBJECT // Your class members go here. // Add..
PyQt: slot is called many times
python,pyqt,signals-slots
The reason why the output is being printed three times, is because of the way you named the signal handlers. The connect slots by name feature will automatically connect signal handlers that are named using the following format: on_[object name]_[signal name] Since the clicked signal has two overloads, and you..
How often are objects copied when passing across PyQt signal/slot connections?
python,pyqt,signals-slots,pyqt5
As suggested by @ekhumoro, I did try, and surprisingly I get a different result to what the test conducted in C++ reveals. Basically, my test shows that: objects are not copied at all, even when passed across thread boundaries using QueuedConnection Consider the following test code: class Object2(QObject): def __init__(self):..
QDialogButtonBox button Ok not woking after connecting
Qt Signals And Slots Tutorial
signals-slots,qt-designer,qdialog
Line: connect(dialogButton, SIGNAL(accepted()), dialog, SLOT(accept())); should be: connect(dialogButton, SIGNAL(accepted()), &dialog, SLOT(accept())); Because the third parameter has to be a memory address(pointer)..
Signals and Slots in Qt4
c++,qt,qt4,signals-slots,qt4.7
Basically you need to connect your signal and slot connect(ui->button1, SIGNAL(clicked()), this, SLOT(yourSlot())); and in this link there is good example about signals and slot: signals and slots in qt..
C++: Thread Safety in a Signal/Slot Library
c++,multithreading,thread-safety,signals-slots
I suspect there is no clearly good answer, but clarity will come from documenting the guarantees you wish to make about concurrent access to an Emitter object. One level of guarantee, which to me is what is implied by a promise of thread safety, is that: Concurrent operations on the..
Calling a C++ function from Qt (slot does not work)
c++,qt,signals-slots
Just register a Qt slot within your header file. class Log { .. Q_SLOTS: void sendMessage (); } and implement the slot in the implementation, e.g. by: Log::sendMessage() { send_message(); } Do not forget to change connect statement to just the sendMessage() function rather than your send_message function..
Qt: Connect inside constructor - Will slot be invoked before object is initialized?
c++,qt,event-handling,signals-slots
You don't have to worry about such scenarios in most cases, because events are delivered in the same thread. There's no 'hidden multithreading' going on you have to care about. If you don't explicitly call a function in the constructor of A that causes events to be processed, you're safe..
Qt Signal Slot Connect
Pyside: Multiple QProcess output to TextEdit
python,pyside,signals-slots,qprocess
Connect the signal using a lambda so that the relevant process is passed to the slot: p.readyReadStandardOutput.connect( lambda process=p: self.write_process_output(process)) def write_process_output(self, process): self.viewer.text_edit.append(process.readAllStandardOutput()) ..
How to declare New-Signal-Slot syntax in Qt 5 as a parameter to function
c++,qt,qt5,signals-slots
You should create template: template<typename Func> void waitForSignal(const typename QtPrivate::FunctionPointer<Func>::Object *sender, Func signal) { QEventLoop loop; connect(sender, signal, &loop, &QEventLoop::quit); loop.exec(); } Usage: waitForSignal(button, &QPushButton::clicked); ..
Qt Signal Slot Parameter
How I can send signal from MouseArea to parent object (TableView)?
qt,tableview,signals-slots
You can propagate it to parent with propagateComposedEvents: true and calling mouse.accepted = false in every needed handler. From doc: Setting accepted to true prevents the mouse event from being propagated to items below this item. Generally, if the item acts on the mouse event then it should be accepted..