Qt хорошо известен своим механизмом сигналов и слотов. Но как это работает? В этом посте мы исследуем внутренности QObject и QMetaObject и раскроем их работу за кадром. Я буду давать примеры Qt5 кода... [Перевод] Как работают сигналы и слоты в Qt Сигналы и слоты, а также система свойств Qt, основываются на возможностях самоанализа объектов во время выполнения программы.Сможете ли вы заметить ключевые слова, которые не являются ключевыми словами C++? signals, slots, Q_OBJECT, emit, SIGNAL, SLOT. Qt 4.5: Signals and Slots 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. Qt: Return value of signal works, why is the official doc… Qt documentation says, return values of signals are not possible: Signals are automatically generated by the moc and must not be implemented in the .cpp file.However, from my trials (Qt 4.8.1) I can tell return values do work: If signal / slot are in the same thread, ConnectionType may be Qt...
Signals are not designed to give you the slots' return values, and there is no guarantee that your example will behave the same way in future versions of Qt. Make sure your code never tries to get the return value of a slot through a signal.
Как работают сигналы и слоты в Qt Qt хорошо известен своим механизмом сигналов и слотов. Но как это работает? В этом посте мы исследуем внутренности QObject и QMetaObject и раскроем их работу за кадром. Я буду давать примеры Qt5 кода... [Перевод] Как работают сигналы и слоты в Qt Сигналы и слоты, а также система свойств Qt, основываются на возможностях самоанализа объектов во время выполнения программы.Сможете ли вы заметить ключевые слова, которые не являются ключевыми словами C++? signals, slots, Q_OBJECT, emit, SIGNAL, SLOT. Qt 4.5: Signals and Slots 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.
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.
Exposing Attributes of C++ Types to QML | Qt QML 5.12.3 Any data that is transferred from C++ to QML, whether as a property value, a method parameter or return value, or a signal parameter value, must be of a type that is supported by the QML engine. QSpinBox Class | Qt Widgets 5.12 allows the user to choose a value by clicking the up/down buttons or pressing up/down on the keyboard to increase/decrease the value currently displayed. Technical FAQ - Qt Wiki
Qt Toolkit - Signals and Slots
It captures the return value from the slots. Expand the code”testSlot2″, and return the last value from the connected slots of the signal. Qt Signals are a syntax sugared interface to the signaling pattern. Slots are the recipients of signal and direct connected signal-slot relationship.
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
When using signals and slots with multiple threads, see Signals and Slots Across Threads.
[quote author="rentner323" date="1390376109"]What i just dont understand, why does it work with return values between Objects running in the same thread, and why not ... How Qt Signals and Slots Work - Woboq - We Create Software Qt is well known for its signals and slots mechanism. ... int value() const { return m_value; } public slots ... The Qt signals/slots and property system are based on ...