Ask Help from beginner
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Hi everybody, I do not know if this is the right place to post my question.
Anyway this is the issue.
I am beginner Qt and C++ amd so I have a lot of doubts.
FIRSTusing the wizzard of Qt I saw a few differnt in creating code but I did not find any explanation in Qt guide:
If i write: Qwidget w; I obtain an Object w with all methods and Propertis and I can acces them with ( . )
I mean w.show() same for QApplication
but when I create for example a label, I write: QLabel Lb=new QLabel();
Can someone explain me:
1 - which is the right way to declare an object
2 - what is the difference between these 2 modes
3 - where can I read the right way in Qt guide?I mean ( point 3 ) when I consult the Qt guide and I check this or other classes, How cab I understand if
I have to use this modality Class_name Object_Name;
orClass_name Object_name= new Class_name();
Please help me
Thanks a lot
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Read a book on C++. It will answer your question. You are asking about the concept of stack and heap based objects, so check the section on pointers. Explaining this here is going a bit far.
Rule of thumb: Use the stack whenever possible (automatic cleanup of objects). Whenever using a QObject derived class using the stack is not possible and you need to use the heap, working with pointers.
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You're right Tobias, with some exceptions to QObject, e.g. when using QFile - which is allocated on the stack even in most of the Qt docs and examples :-)
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You should follow the Tobias suggestion, having a solid C++ background is pretty useful when learning Qt.
Probably you already know it but, the "Thinking in C++":http://www.mindview.net/Books/TICPP/ThinkingInCPP2e.html is a great book that you can get download for free.Anyway the Qt Object Model is a subject on its own, that needs its own explanation, a nice one (with pretty figures :D), is in the L2 "Presentation with notes" of the "Qt Learning material":http://qt.nokia.com/services-partners/qt-in-education/qt-in-education-course-material, altough this material is intended to be used for teaching Qt I think it's clear enough even for the beginners.
And if you're looking for more detailed explanations check the "Qt eLearning videos":http://qt.nokia.com/developer/learning/elearning, specially the "Qt Training modules":http://qt.nokia.com/developer/learning/online/training/modules your question is answered in the "Objects int Qt" ones.
Happy learning!
