Slot Example Qt
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Example SLOT/SIGNAL between two object QT. Ask Question Asked 3 years, 9 months ago. Active 3 years, 2 months ago. Viewed 5k times 1. My app, consists in 2. In Qt, we have an alternative to the callback technique: We use signals and slots. A signal is emitted when a particular event occurs. Qt's widgets have many predefined signals, but we can always subclass widgets to add our own signals to them. A slot is a function that is called in. QtCore.QObject.connect(button, QtCore.SIGNAL(“clicked”), slotfunction). Button.clicked.connect(slotfunction) Example. In the following example, two QPushButton objects (b1 and b2) are added in QDialog window. We want to call functions b1clicked and b2clicked on clicking b1 and b2 respectively. 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.
Unlike a console mode application, which is executed in a sequential manner, a GUI based application is event driven. Functions or methods are executed in response to user’s actions like clicking on a button, selecting an item from a collection or a mouse click etc., called events.
Widgets used to build the GUI interface act as the source of such events. Each PyQt widget, which is derived from QObject class, is designed to emit ‘signal’ in response to one or more events. The signal on its own does not perform any action. Instead, it is ‘connected’ to a ‘slot’. The slot can be any callable Python function.
In PyQt, connection between a signal and a slot can be achieved in different ways. Following are most commonly used techniques −
A more convenient way to call a slot_function, when a signal is emitted by a widget is as follows −
Qt Signal Slot Example C
Suppose if a function is to be called when a button is clicked. Here, the clicked signal is to be connected to a callable function. It can be achieved in any of the following two techniques −
or
Example
In the following example, two QPushButton objects (b1 and b2) are added in QDialog window. We want to call functions b1_clicked() and b2_clicked() on clicking b1 and b2 respectively.
When b1 is clicked, the clicked() signal is connected to b1_clicked() function
Qt5 Slot Example
Qt Signal Slot Example
When b2 is clicked, the clicked() signal is connected to b2_clicked() function
Slot Example Qtc
Example
The above code produces the following output −