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Qt No Such Slot In Derived Class

 
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  • I'm at a loss for why this issue is coming up. I've got QOBJECT in the header, the slot is included in: private slots: void slotname; Everything is spelled the same, all the other answers I've found either don't apply or I've already checked to see if they were the cause.
  • The type of such pointers includes the return type, the class which owns the member, the types of each argument and the const-ness of the function. You cannot really convert pointer to member functions to anything and in particular not to void. because they have a different sizeof.

There is no such slot - 'display(5)'. (But there is 'display(int)')Parameters to slots are automatically passed from signals. As there is no 'clicked(int)', it would be best for you to create a new class derived from QLCDNumber and create a new slot in it. Something like the code below.

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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 −

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

When b2 is clicked, the clicked() signal is connected to b2_clicked() function

Qt No Such Slot In Derived Classroom

Example

Qt No Such Slot In Derived Classes

The above code produces the following output −

Qt No Such Slot In Derived Class C

Output