Mastering Qt 5

Emitting a custom signal using lambdas

The remove task is straightforward to implement, but we'll study some new concepts along the way. The Task has to notify its owner and parent (MainWindow) that the removeTaskButtonQPushButton has been clicked. We'll implement this by defining a custom signal removed in Task.h files:

class Task : public QWidget 
{ 
    ... 
public slots: 
    void rename(); 
signals: 
    void removed(Task* task); 
   ... 
}; 

Like we did for the slots, we have to add the Qt keyword signals in our header. Since a signal is used only to notify another class, the public keyword is not needed (it even raises a compilation error). A signal is simply a notification sent to the receiver (the connected slot); it implies that there is no function body for ...