Referencing Parent Widget from Child

[yop]

I'd like to do that class cast, but I can't because my child widget class has no knowledge of the parent class (i.e. I'm not including the parent.h file or anything).

When you are starting to put those little arrows one after the other the compiler generates indermediate objects / pointers to objects, so not including the interface of the generated objects the compiler won't know what to do and also you can only have access to the public interface:

parent()->DoSomething();

parent()->DoSomething();

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is actually

QObject * temp = parent();
temp->DoSomething(); // boom

QObject * temp = parent();
temp->DoSomething(); // boom

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while you need

#include "myform.h"
//...
MyForm *temp = (MyForm *)parent();
temp->DoSomething()

#include "myform.h"
//...
MyForm *temp = (MyForm *)parent();
temp->DoSomething()

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[Lebowski]

while you need

#include "myform.h"
//...
MyForm *temp = (MyForm *)parent();
temp->DoSomething()

#include "myform.h"
//...
MyForm *temp = (MyForm *)parent();
temp->DoSomething()

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I tried that but I'm getting segmentation fault which means that I'm getting the wrong pointer from parent().

[fullmetalcoder]

I tried that but I'm getting segmentation fault which means that I'm getting the wrong pointer from parent().

did you checked the validity of the casted pointer ???
basically, you should test for a NULL pointer each time you need to access such a pointer...

if ( !temp )
 qDebug("crap!!!");
else
 temp->doSomething()

if ( !temp )
 qDebug("crap!!!");
else
 temp->doSomething()

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That would do! If you get the "crap!!!" message, check the validity of your algorithm (I mean, be sure that you're not working with the bad pointer type) or try other ways of casting your pointer (RTTI may help).

[wysota]

You can use dynamic_cast or qobject_cast here to stand a chance when guessing the parent type.