How to detect page change in QWizard?

JonB

@Mads030306 said in How to detect page change in QWizard?:

I already tried using that signal but couldn't get it to work.

Then show your code. "couldn't get it to work" might mean wouldn't compile, didn't connect() successfully, ran and called the slot but whatever you did in the slot didn't work or never called the slot.

Which object is the sender and how do i create a slot?

The QWizard is the sender and you would create a slot for it like any slot for a signal. Let's see what you attempted. (Just for this bit, not your whole program!)

Mads030306

class Handler : public QObject
{
    Q_OBJECT

    public slots:
        void next();
};



void Handler::next(){
    std::cout << "Debug";
}

    //this is in my main function
    Handler /***/handler/* = new Handler()*/;

    wizard.connect(&wizard, SIGNAL ( QWizard::currentIdChanged(int) ), &handler, SLOT ( Handler::next ));

jsulm

@Mads030306 Please be more specific: did you put your Handler class in its own header/cpp files?

JonB

@Mads030306 said in How to detect page change in QWizard?:

wizard.connect(&wizard, SIGNAL ( QWizard::currentIdChanged(int) ), &handler, SLOT ( Handler::next ));

Your syntax is wrong. Please, please change over to New Signal Slot Syntax --- which has been around for years ever since Qt5 --- and it will stop you doing this. Get rid of all SIGNAL/SLOT() macros. Life will be so much easier/cleaner.

I could tell you what you need in old style but it would be much better for you if you change over, so do that first....

Mads030306

@JonB
I have changed to the new method but still get the same error.

wizard.connect(&wizard, &QWizard::currentIdChanged, &handler, &Handler::next);

Do i have to specify the parameter of &QWizard::currentIdChanged like before (SIGNAL ( QWizard::currentIdChanged(int) ))?

JonB

@Mads030306
OK, that new syntax is a big improvement!

With that for " still get the same error" do you still get that error which is a linker error or do you get a compiler error? If it's a compiler error, it's not "the same" (in which case please show the new error message).

Depending on answer, it looks like you are not linking with the module for Handler....

Do i have to specify the parameter of &QWizard::currentIdChanged like before (SIGNAL ( QWizard::currentIdChanged(int) ))?

No. Rather the signature for slot Handler::next(...) must "match" the signature for signal QWizard::currentIdChanged(). Show your signature for Handler::next(...) definition if not sure.

Mads030306

@JonB
i get a compile error (the one in the picture in the other post).

On the signal and slots documentation i found something about the error i get, i need to run something called moc but i dont know how to run it.

The Q_OBJECT macro is expanded by the preprocessor to declare several member functions that are implemented by the moc; if you get compiler errors along the lines of "undefined reference to vtable for LcdNumber", you have probably forgotten to run the moc or to include the moc output in the link command.

Also what is linking and how do i do it.

JonB

@Mads030306 said in How to detect page change in QWizard?:

i need to run something called moc but i dont know how to run it.

Also what is linking and how do i do it.

All this is done for you by the build process, assuming your project is correctly defined in the .pro file.

Show your signature for Handler::next(...). Also confirm in the .h file it is in section public slots:. I need to check that anyway.
Show your declaration of class Handler. Since it is using signals/slots, does it have a line reading just Q_OBJECT immediately after the { of the class declaration in the .h file?

(Essentially just show the whole of the class Handler declaration in the .h [not .cpp!] file.)

Mads030306

I dont have a header file, i only have the folowing code and it is in the main cpp file.

class Handler : public QObject
{
    Q_OBJECT

    public slots:
        void next();
};



void Handler::next(){
    std::cout << "Debug";
}

Do i have to move my class into a header file and include that header?

jsulm

@Mads030306 said in How to detect page change in QWizard?:

I dont have a header file, i only have the folowing code and it is in the main cpp file

Please move your Handler class in its own header and cpp files! Classes which subclass QObject needs to be in their own header/cpp files in order for moc to be able to process them.

JonB

@Mads030306 said in How to detect page change in QWizard?:

Do i have to move my class into a header file and include that header?

Not necessarily, unless we find that moc does not like multiple classes with Q_OBJECT in them in one source file or only likes them in a .h file, which I do not know....

Can we confirm that this class Handler you show is placed in the source file above/before the compiler meets the wizard.connect(&wizard, &QWizard::currentIdChanged, &handler, &Handler::next); line?

UPDATE
According to e.g. https://forum.qt.io/topic/12388/q_object-in-cpp-file we are not going to do well with Q_OBJECT class in a .cpp file. By far the simplest will be to split it:

Create a new handler.cpp & handler.h file in your project (from the Qt Creator wizard which allows you to add a new class-file, so that the .pro gets updated right).
Move your Handler definition code into the .cpp.
Move your Handler declaration code into the .h.
Do a complete qmake/rebuild, and see what you get.

When that is working you will want to change your Handler::next() slot to accept the int id parameter that QWizard::currentIdChanged(int id) will be passing to it. From that you will be able to find out about which page change is happening.

Mads030306

It works now.

Thank you for helping :)

Sorry for my dumb questions, im very new to c++ and qt.