Refactoring if-else in Qt - c++

Question

I have a few keys that can be pressed, and each key press emits a signal that corresponds to it. However, the key presses do different things depending on which object is being operated on. I have an example illustration below.
// keyboard.cpp
void receive_key_press(uint8_t key_id){
if(key_id == 1)
emit key_one_pressed();
else if(key_id == 2)
emit key_two_pressed();
else if(key_id == 3)
emit key_three_pressed();
}
Class A : public QObject {
// use Q_PROPERTY here to expose the member var 'model' to qml
public:
int model;
}
int main(){
Keyboard keyboard;
A obj;
if (some_condition)
obj.model = 5;
else
obj.model = 7;
// Engine initialization here and exposing 'obj' and 'keyboard' to qml using setContextProperty
}
Then in main.qml
Connections {
target: keyboard
onKey_one_pressed: {
if (obj.model == 5)
// do something
else
// do something else
// execute some common code here
}
onKey_two_pressed: {
if (obj.model == 5)
// do something
else
// do something else
}
onKey_three_pressed: {
if (obj.model == 5)
// do something
else
// do something else
}
}
How can I simplify and avoid all those if-else conditions in the main.qml. Is there something in Qt that can make this easier, and provide some global way of handling a 'Gui state'. I know there's like a File Selector in Qt but that's not really what I'm going for. I want to have a better approach instead of having if-else everywhere in the Gui for different model.
Thanks in advance

Answer 1

In your particular example, factor it out into a common function:
Connections {
target: keyboard
function commonCode() {
// execute some common code here
}
onKey_one_pressed: {
if (obj.model == 5)
// do something
else
// do something else
commonCode();
}
onKey_two_pressed: {
if (obj.model == 5)
// do something
else
// do something else
commonCode();
}
onKey_three_pressed: {
if (obj.model == 5)
// do something
else
// do something else
commonCode();
}
}
You can also put commonCode in a more broadly accessible place to further reduce code duplication.
However, there is also QML States: https://doc.qt.io/qt-5/qtquick-statesanimations-states.html
This is a very handy way to manage different configurations of your GUI. You can use PropertyChanges with it to override the signal handler of objects based on your model value.