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Thread: Regarding syntax

  1. #1
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    Default Regarding syntax

    Hi!!

    I haven't yet undrstood the syntax of inheritance in QT.

    For example, the directory browser example code says->

    1. class FileItem : public QListViewItem
    2. {
    3. public:
    4. FileItem( QListViewItem *parent, const QString &s1, const QString &s2 )
    5. : QListViewItem( parent, s1, s2 ), pix( 0 ) {}
    6.
    7. const QPixmap *pixmap( int i ) const;
    8. void setPixmap( QPixmap *p );
    9.
    10. private:
    11. QPixmap *pix;
    12.
    13. };

    the lines 4 and 5, does the construtor of class FileItem inherit the constructor of class QListViewItem??. the syntax is confusing.. I think the constructors are overloaded. Or is it the way of overloading. Please guide me as i am unable to understand what lines 4 & 5 mean.

  2. #2
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    Default Re: Regarding syntax

    This is a C++ issue about constructors that every basic C++ book covers this topic.
    When you call the constructor of FileItem, it will call the constructor inherited from QListViewItem passing the given arguments. Also you got the constructor for QPixmap initializing it to 0. This is what those lines are doing.
    Misha R.evolution - High level Debugging IDE

    Programming is about 2 basic principles: KISS and RTFM!!!

  3. The following user says thank you to Archimedes for this useful post:

    Yayati.Ekbote (27th January 2010)

  4. #3
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    Default Re: Regarding syntax

    Hi,

    the lines 4 and 5, does the construtor of class FileItem inherit the constructor of class QListViewItem??
    Clearly you have to review ur c++ basics here.


    the syntax is confusing.. I think the constructors are overloaded. Or is it the way of overloading.
    In c++, constructors can be overloaded.
    Ex.
    Qt Code:
    1. class TEST_CLASS_FOR_YOU
    2. {
    3. TEST_CLASS_FOR_YOU();
    4. TEST_CLASS_FOR_YOU(int a);
    5. TEST_CLASS_FOR_YOU(int a,int b);
    6. }
    To copy to clipboard, switch view to plain text mode 

    for furthur please refer this link http://www.cplusplus.com/doc/tutorial/



    No going back the example.

    4. FileItem( QListViewItem *parent, const QString &s1, const QString &s2 )
    5. : QListViewItem( parent, s1, s2 ), pix( 0 ) {}
    This is defination of constructor FileItem which is derived from QListViewItem class. QListViewItem class has overloaded constructor QListViewItem( parent, s1, s2 ) which is called at initillization. this is not a defination of QListViewItem( parent, s1, s2 ) class remember.

  5. The following user says thank you to vishwajeet.dusane for this useful post:

    Yayati.Ekbote (27th January 2010)

  6. #4
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    Default Re: Regarding syntax

    thanks for the reply.
    Last edited by Yayati.Ekbote; 27th January 2010 at 15:20.

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