E.g. with Qt::SingleConnection there is no risk of multiple slots, with Qt::BlockingQueuedConnection there is only one return value at a time. "Never have a return value" (doc) is different to use wisely IMHO. All the above true, there might be side effects, but still many use cases where return values … c++ - QT signal and slot function signature - Stack Overflow Your slots can return a value. However, if the slot is connected to a signal and called when the signal is emitted, the return value will be ignored. But the slot is a normal member function and can be called like any other function. In this case, the return value can be used by the caller. This is said in the document you link to : Function with Signals & Slots | Qt Forum @gabor53 You should read again about Qt signals/slots. They are used for asynchronous communication and to react on user interactions. That means if you connect the clicked() signal of a button to a slot that slot will be called when user presses the button. Can Qt signals return a value? - ExceptionsHub Nov 22, 2017 · Questions: Boost.Signals allows various strategies of using the return values of slots to form the return value of the signal. E.g. adding them, forming a vector out of them, or returning the last one. The common wisdom (expressed in the Qt documentation [EDIT: as well as some answers to this question ]) is that no
SlotType::ReturnType, typename SignalType::ReturnType>::value), 29 " Return type of the slot is not compatible with the return type of the signal. "); 30 31 const int *types = 0; if ...
Slot return value - what if it would be not lost? | Qt Forum The very fact that a return value or something like that is required for proper operation, means that signal/slot is not the right approach for Gourmand. He would probably be better off using invokeMethod() as you state or just call the function he How can I return a value from SLOT in Qt5? - Stack Overflow 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 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 Signals & Slots | Qt Core 5.12
MI-PYT: GUI v Pythonu
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. Qt - A Small Example | qt Tutorial Signals and slots are used for communication between objects. The signals and slots mechanism is a central feature of Qt and probably the part that differs most from the features provided by other frameworks. The minimal example requires a class with one signal, one slot and one connection: counter.h [QTBUG-23488] Socket options return strange values - Qt ...
Mar 9, 2017 ... we can test the return value (for instance, by adding an assertion), or ... Qt automatically breaks a signal/slot connection if either the sender or ...
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. PyQt/Sending Python values with signals and slots - Python Sending Python values with signals and slots. On the #pyqt channel on Freenode, Khertan asked about sending Python values via Qt's signals and slots mechanism. The following example uses the PyQt_PyObject value declaration with an old-style signal-slot connection, and again when the signal is emitted, to communicate a Python dictionary. Interacting with QML Objects from C++ | Qt QML 5.12.3 Interacting with QML Objects from C++ All QML object types are QObject -derived types, whether they are internally implemented by the engine or defined by third-party sources . This means the QML engine can use the Qt Meta Object System to dynamically instantiate any QML object type and … QSpinBox Class | Qt Widgets 5.12.3 - Qt Documentation This signal is emitted whenever the spin box's value is changed. The new value's integer value is passed in i. Note: Signal valueChanged is overloaded in this class. To connect to this signal by using the function pointer syntax, Qt provides a convenient helper for obtaining the …
c++ - Can Qt signals return a value? - Stack Overflow
Jul 9, 2018 ... Signals should support non-void return values (of little importance in ... wrappers named "slot" which support between 0 and 16 arguments, this ... Creating advanced dialogs and windows — itom Documentation The dialog is closed and the return value in modal style is 1. .... Qt provides the possibility to connect a signal with a slot, under the only condition, that both have ...
c++ - QT return value from a signal? - Stack Overflow