Cannot write a function pointer into a class implementation

[tonnot]

I have a MainWindow class with ther .h and cpp files.
Compiler tells me :

argument of type 'void (MainWindow:(long int)' does not match 'void (*)(long int)'

I have tried all combinations, with class prefix, without it,.... without success.

void MainWindow::update1(long value){ }
 
void MainWindow::on_pushButton_6_clicked()
{
    void (*pFunc)(long);
    pFunc = update1;        // here is where I have the error.
 
}

void MainWindow::update1(long value){ }

void MainWindow::on_pushButton_6_clicked()
{
    void (*pFunc)(long);
    pFunc = update1;        // here is where I have the error.

}

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Any help ? Thanks

[squidge]

You are declaring a C function pointer but attempting to assign a C++ function. This is not possible. You must define the class instance as well.

eg. void(MainWindow::*pFunc)(long)

[tonnot]

Ok, so simple....
Thanks

---

Added after 1 15 minutes:

And how can I write it to pass to a function of another class ??
How I can define this class_B function to receive pointers of functions of any parent class ?

[wysota]

And how can I write it to pass to a function of another class ??

You change "MainWindow" in the pointer declaration to the class of your choice.

How I can define this class_B function to receive pointers of functions of any parent class ?

You use the parent class name in the pointer declaration.

[tonnot]

So, I cannot write a generic class body to accept function pointers of any class ?
Thanks

[squidge]

The compiler needs to know the class otherwise it doesn't know how to access the class member variables (the 'this' keyword wouldn't work)

However, you can create a standard function, use a C-style function pointer and then make it a friend of the relevent class. You will however have to pass a pointer to the class instance if you require to access any class member functions or variables as a standard C function pointer will not populate 'this'.

[wysota]

So, I cannot write a generic class body to accept function pointers of any class ?
Thanks

Usually you do it the other way round. You expose a generic interface (using virtual methods) which is then implemented by some class so that another class/object can call methods of the interface. Just like Designer handles custom widgets.

[tonnot]

Ok, thank you very much