qt - How to handle QComboBox signals in inner classes -

i using qt5 , have created class "outer" "inner" class. "inner" class has 2 qcombobox "cb1" , "cb2" objects private variables.

in principle, displayed text of second qcombobox, "cb2", depends of current text of first qcombobox "cb1". in fact, easy implement connection between these two, using signals , slots writing appropriate slot.

the problem qt not support writing slots inside inner class. makes me confused.

how can handle connection between these 2 qcomboboxes in "inner" class?

for code,

class outer : public qdialog {   q_object   // private variables;    class inner : public qwidget   {     qcombobox *cb1, *cb2;     // other variables;     public:     // public methods     public slots:     void setindex(int i);   };   // other things; }; 

inner implementation

outer::inner::inner() {   // useless things;   connect(cb1, signal(currentindexchanged(int)), this, slot(setindex(int))); }  outer::inner::setindex(int i) {   // stuff retrieve correct index in cb2; } 

in qt 5, method can connected signal, whether marked slot or not, describing non problem.

you need use modern connect syntax, , work fine:

connect(cb1, &qcombobox::currentindexchanged, this, &outer::inner::setindex); 

of course, nothing else work correctly: qobject_cast mechanism won't work, metadata wrong, etc.

an inner class cannot qobject. fail see point of it. make local class in .cpp file instead of inner class.