how to override QState and use it

AndreAhmed

I'm trying to override QState functions onEntry and onExist by its child class . How would I call the constructor of the QState. I'm so confused about reimplementing the QState .


class s : public QState
{
public:
    s(QState *parent = 0);
    ~s();
protected:
    void onEntry(QEvent *event) override;
    void onExit(QEvent *event);

};
void s::onEntry(QEvent *event)
{
    qDebug("on enter");
}

void s::onExit(QEvent *event)
{

}

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    s * state = new s();
}
and QState is like:

class QState
{
protected:
     .
     .
public:
     void onEntry(QEvent *event);
     void onEntry(QEvent *event)

};

mrjj

hi
you call your base class constructor like this
s::s(QWidget* parent) : QState(parent) {}

AndreAhmed

so I have to have a dummy initial state and then pass it to the abouve s::(QWidget*parent) ?

mrjj

@AndreAhmed
From your own constructor, you also call base class constructor
as part of constructing your QState child.

AndreAhmed

what should I pass a dummy QState or a QStatemachine ?

mrjj

@AndreAhmed
I think u can pass a Dummy but not sure u need to do it?

mrjj

hi
this sample also inherited QState
http://doc.qt.io/qt-5/qtwidgets-statemachine-pingpong-example.html

AndreAhmed

do you know how should I keep the state active until a condition occurs ? How to implement that ?

mrjj

@AndreAhmed
well a given state is active when no Transition has happened.

do you mean like a function being called over and over while in a state?

AndreAhmed

yes I mean a function that's called over and over , then after a condition like if(cnt==5) go to next state.

AndreAhmed

a giving state is active but it only calls onEnter() just once.

mrjj

@AndreAhmed
Hi
Look here
https://doc.qt.io/archives/4.6/statemachine-trafficlight.html

They use a timer.
You could do the same and simply enable onEnter
and turn off onExit.

AndreAhmed

hi,

thanks for the answer. How would I put a timer for onEntry() I'm so confused

mrjj

@AndreAhmed
Add a QTimer timer; to your state
add a slot to your state
connect timer to slot

OnEnter
timer.start(1000); // call ur slot every 1 sec

OnExit
timer.stop();

AndreAhmed

Can I say addtransition inside the slot of the timer so that to move to another state ?

how to manage states then, they should be in one cpp file ?

mrjj

@AndreAhmed
You can use any normal QState function in the slot to advance state.

Well, I guess keeping related states in same cpp sounds like good plan.

You did see
http://doc.qt.io/qt-5/statemachine-api.html
?

AndreAhmed

Yes I did but didn't know how to use the classes of the QState,..etc.

So the steps now

Inherit from QState and implement onEnter on Exit
make a timer
start the timer in onEnter()
do the logic inside the slot of the timer
add the transition there

mrjj

hi
Yes something like that. Please make Timer a class member.

Just a note:
Well it has signals also
void entered()
void exited()
http://doc.qt.io/qt-5/qabstractstate.html#entered
So you dont need to subclass to use Enter/exit.