c++ - Can Qt signals return a value? - Stack Overflow The constructor wires up two slots to the testSignal signal, and then emits the signal. It captures the return value from the slot(s) invoked. Unfortunately, you only get the last return value. If you evaluate the code above, you'll get: "testSlot2", the last return value from the connected slots of the signal. Getting a return value from an emitted signal | Qt Forum Qt::DirectConnection 1 The slot is invoked immediately, when the signal is emitted. So I thought I could do something like i wrote above. If I well understood so the problem is that I cannot make any assumptions on if the return statement of the slot will be executed before … c++ - How can I return a value from SLOT in Qt5? - Stack Therefore slot return types are useless when invoked through a signal (even though you can still use them when you invoke a slot directly, ie if it's a member function). That being said, you can capture ui or even better plainLineEdit by reference or by address in your slot (ie if it's a lambda) and set correctly the string from there.
Qt Signals & Slots: How they work | nidomiro
Signals and Slots in PySide. From Qt Wiki (Redirected from Signals and slots in PySide) Redirect page. Jump to: ... Redirect to: Qt for Python Signals and Slots; Qt signals and slots for newbies - Qt Wiki function to relate the signal to the slot. Qt's signals and slots mechanism does not require classes to have knowledge of each other, which makes it much easier to develop highly reusable classes. Since signals and slots are type-safe, type errors are reported as warnings and do not cause crashes to occur. For example, if a Quit button's New Signal Slot Syntax - Qt Wiki
Qt itself will not throw exceptions. Instead, error codes are used. In addition, some classes have user visible error messages, for example QIODevice::errorString() or QSqlQuery::lastError(). This has historical and practical reasons …
Qt 4.8: QDialog Class Reference The QDialog class is the base class of dialog windows. A dialog window is a top-level window mostly used for short-term tasks and brief communications with the user. QDialogs may be modal or modeless. QDialogs can provide a return value, and they can have default buttons. 20 ways to debug Qt signals and slots | Sam Dutton’s blog Below are some suggestions for troubleshooting signals and slots in the Qt C++ library. 1. Check for compiler warnings about non-existent signals and/or slots. 2. Use break points or qDebug to check that signal and slot code is definitely reached: – the connect statement – code where the signal is fired – the slot code. 3. Signals and slots - Mastering Qt 5
I have to return the QString in the slot to the newServerConn() function and from there to a function in MainWindow class because only then I would be able to print the string to the plainLineEdit widget pointed by the ui object. Question 1: How can I return a value from the slot?
c++ - Qt: meaning of slot return value? - Stack Overflow This is passed by QMetaObject::invokeMethod. So the return value in the moc generated code is saved and passed back to the caller. So for normal signal-slot interactions the return value is not used for anything at all. However, the mechanism exists so that Getting a return value from an emitted signal | Qt Forum
Signals and Slots | Introduction to GUI Programming with Python and Qt
Qt MOOC | Part 2 - GitHub Pages void Counter::setValue(int value) { if (value != m_value) ... When this happens, the signals and slots mechanism is totally ... Execution of the code following the emit statement will occur once all slots have returned.
Connecting signals from QML to Python using a top-level QML signal. If you prefer to handle the signal connection in Python, the simplest way to do it is to declare a top-level signal in QML and connect that to a Python slot as shown in example qmltopy3. First, in the top-level QML item, declare the signal: Qt: Signals & Slots - PUC-Rio Signals and slots are loosely coupled: A class which emits a signal neither knows nor cares which slots receive the signal. Qt's signals and slots mechanism ensures that if you connect a signal to a slot, the slot will be called with the signal's parameters at the right time. Signals and slots can take any number of arguments of any type. PySide/PyQt Tutorial: Using Built-In Signals and Slots ...