QList & QPointer to store object list

[maddog_fr]

It's exact.

WindowList.prepend(new HTMLWindow());

WindowList.prepend(new HTMLWindow());

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create a window that is not destroyed at the end of the method
but

WindowList.at(0).setGeometry(QRect(100,100,285,110));

WindowList.at(0).setGeometry(QRect(100,100,285,110));

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generate this error : const class QPointer<HTMLWindow>' has no member named 'setGeometry'

I guess it's normal because the QList contains pointers to HTMLWindow(s) object
but how to use the object referenced by pointers ?

that's why i used HTMLWindow(WindowList.at(n)). it is how i do Typecast in Delphi.

[faldzip]

You should read some books about C++ basics I think...
And QPointer behaves in the same way as normal pointer, so getting back to one of the first lessons about C++ and pointers you will see that:
1. If you want to reference the member of the object you use '.' operator:

SomeClass obj;
obj.someMemberFunction();

SomeClass obj;
obj.someMemberFunction();

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2. But if you want to reference the member of the object, but you have only the pointer to that object, you have to use '->' operator:

SomeClass *obj = new SomeClass;
obj->someMemberFunction();

SomeClass *obj = new SomeClass;
obj->someMemberFunction();

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And a QPointer<SomeClass> behaves exactly in same way as SomeClass * so you have to use -> operator to get the members from object pointed by a QPointer.

But you are trying to do very weird things, which are not even supposed to work:

HTMLWindow(WindowList.at(n));

HTMLWindow(WindowList.at(n));

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You are storing QPointer<HTMLWindow> in your list so:

WindowList.at(n)

WindowList.at(n)

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returns a QPointer that points to some object of HTMLWindow class, and it can be used like normal pointer, so the line:

HTMLWindow(WindowList.at(n));

HTMLWindow(WindowList.at(n));

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creates a new HTMLWindow object on a stack (a local variable in other words) with a existing HTMLWindow on index 'n' in your list as a parent because in that case the:

WindowList.at(n)

WindowList.at(n)

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is casted to QWidget *, if constructor of the HTMLWindow looks like :

HTMLWindow(QWidget *parent);

HTMLWindow(QWidget *parent);

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And what you are trying to do is to cast the pointer to an object to instance of that object which obviously should fail, because how do you think the 32-bit (or more) integer value which the memory address of the object can be casted to that object, the whole HTMLWindow???

The next thing is that (as I said before) if this:

WindowList.at(0);

WindowList.at(0);

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returns the first element of your list, which is of type QPointer, doing like this:

WindowList.at(0).setGeometry(QRect(100,100,285,110));

WindowList.at(0).setGeometry(QRect(100,100,285,110));

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is trying to use the setGeometry() method of a QPointer object, which, as I suppose, does not have the setGeometry() method. If you want to use the setGeometry() of the HTMLWindow oobject pointed by this QPointer you have to use '->' operator:

WindowList.at(0)->setGeometry(QRect(100,100,285,110));

WindowList.at(0)->setGeometry(QRect(100,100,285,110));

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So, first of all, it is C++, not Delphi, so maybe you should find some time to learn some C++ basics before you start coding with it...

[maddog_fr]

You are right. I found out by myself that using -> instead of . was working
but i didnt really understand why.

I will follow your advice and take some information about c++ pointers that seems to be really different from delphi.

thx for ur help all.

[maddog_fr]

You should read some books about C++ basics I think...

So, first of all, it is C++, not Delphi, so maybe you should find some time to learn some C++ basics before you start coding with it...

Just for your information I am learning by example. Just reading a book is too boring.
Maybe it's a slower method but i am not sure. I learned Delphi without opening a book (just learned a bit turbo pascal at school when i was young). Throwning peoples sentences like "go to read C++ basics first" is not a good way to make people like a language. For me pointers are not basic part of C++. thx anyway.

[faldzip]

Pointers are used every where in C and C++, and especially in Qt where all your widgets should be made on heap and kept with pointer's - so learning about pointers is necessary. And reading a book can help you understand, why -> is working and . is not working.