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Thread: class operator problem

  1. 22nd May 2008, 17:39 #1
    MarkoSan's Avatar
    MarkoSan
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    Default class operator problem

    Hi to all!

    I have following chunk of code:
    Qt Code: 
    1. bool CMerchandizeOrder::operator==(const CMerchandizeOrder& comparedOrder) const
    2. {
    3.     bool flag1=false;
    4.     bool flag2=false;
    5.     bool flag3=false;
    6.     bool flag4=false;
    7. //    bool flag5=false;
    8.     bool flag6=false;
    9.  
    10.     if(merchandizeID()==comparedOrder.merchandizeID())
    11.         flag1=true;
    12.     if(merchandizeQuantity()==comparedOrder.merchandizeQuantity())
    13.         flag2=true;
    14.     if(merchandizePrice()==comparedOrder.merchandizePrice())
    15.         flag3=true;
    16.     if(merchandizeSubtotal()==comparedOrder.merchandizeSubtotal())
    17.         flag4=true;
    18. /*
    19.     if(this->m_strDisplayString==comparedOrder.merchandizeDisplayString())
    20.         flag5=true;
    21. */
    22.     if(merchandizeName()==comparedOrder.merchandizeName())
    23.         flag6=true;
    24.     if(flag1==true && flag2==true && flag3==true && flag4==true /*&& flag5==true*/ && flag6==true)
    25.         return true;
    26.     return false;
    27. }
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    When i try to compile it i get following errors:
    Qt Code: 
    1. mingw32-make 
    2. mingw32-make -f Makefile.Debug
    3. mingw32-make[1]: Entering directory `C:/Documents and Settings/markofr/workspace/Client'
    4. g++ -c -g -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_SQL_LIB -DQT_GUI_LIB -DQT_CORE_LIB -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\..\..\Qt\4.4.0\include\QtCore" -I"..\..\..\..\Qt\4.4.0\include\QtCore" -I"..\..\..\..\Qt\4.4.0\include\QtGui" -I"..\..\..\..\Qt\4.4.0\include\QtGui" -I"..\..\..\..\Qt\4.4.0\include\QtSql" -I"..\..\..\..\Qt\4.4.0\include\QtSql" -I"..\..\..\..\Qt\4.4.0\include" -I"c:\Qt\4.4.0\include\ActiveQt" -I"debug" -I"." -I"..\..\..\..\Qt\4.4.0\mkspecs\win32-g++" -o debug\CMerchandizeOrder.o CMerchandizeOrder.cpp
    5. CMerchandizeOrder.cpp: In member function `bool CMerchandizeOrder::operator==(const CMerchandizeOrder&) const':
    6. CMerchandizeOrder.cpp:32: error: passing `const CMerchandizeOrder' as `this' argument of `const qint16 CMerchandizeOrder::merchandizeID()' discards qualifiers
    7. CMerchandizeOrder.cpp:32: error: passing `const CMerchandizeOrder' as `this' argument of `const qint16 CMerchandizeOrder::merchandizeID()' discards qualifiers
    8. CMerchandizeOrder.cpp:34: error: passing `const CMerchandizeOrder' as `this' argument of `const qint16 CMerchandizeOrder::merchandizeQuantity()' discards qualifiers
    9. CMerchandizeOrder.cpp:34: error: passing `const CMerchandizeOrder' as `this' argument of `const qint16 CMerchandizeOrder::merchandizeQuantity()' discards qualifiers
    10. CMerchandizeOrder.cpp:36: error: passing `const CMerchandizeOrder' as `this' argument of `const qreal CMerchandizeOrder::merchandizePrice()' discards qualifiers
    11. CMerchandizeOrder.cpp:36: error: passing `const CMerchandizeOrder' as `this' argument of `const qreal CMerchandizeOrder::merchandizePrice()' discards qualifiers
    12. CMerchandizeOrder.cpp:38: error: passing `const CMerchandizeOrder' as `this' argument of `const qreal CMerchandizeOrder::merchandizeSubtotal()' discards qualifiers
    13. CMerchandizeOrder.cpp:38: error: passing `const CMerchandizeOrder' as `this' argument of `const qreal CMerchandizeOrder::merchandizeSubtotal()' discards qualifiers
    14. CMerchandizeOrder.cpp:44: error: passing `const CMerchandizeOrder' as `this' argument of `const QString CMerchandizeOrder::merchandizeName()' discards qualifiers
    15. CMerchandizeOrder.cpp:44: error: passing `const CMerchandizeOrder' as `this' argument of `const QString CMerchandizeOrder::merchandizeName()' discards qualifiers
    16. mingw32-make[1]: *** [debug/CMerchandizeOrder.o] Error 1
    17. mingw32-make[1]: Leaving directory `C:/Documents and Settings/markofr/workspace/Client'
    18. mingw32-make: *** [debug] Error 2
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    What does that mean and how do I get rid of these errors?!
    Qt 5.3 Opensource & Creator 3.1.2
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  2. 22nd May 2008, 17:56 #2
    jpn
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    Default Re: class operator problem

    You are calling non-const methods in a const method (and via const reference). CMerchandizeOrder::merchandizeID() etc. should be const methods just like the operator is.
    J-P Nurmi
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  3. 22nd May 2008, 18:05 #3
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    MarkoSan
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    Default Re: class operator problem

    But they are const:
    Qt Code: 
    1. inline const qint16 merchandizeID()
    2.         { return m_OrderValues.iMerchandizeID; };
    3.     inline void setMerchandizeID(qint16 iMerchandizeID)
    4.         { m_OrderValues.iMerchandizeID=iMerchandizeID; };
    5.  
    6.     inline const QString merchandizeName()
    7.         { return m_OrderValues.strMerchandizeName; };
    8.     inline void setMerchandizeName(QString& strName)
    9.         { m_OrderValues.strMerchandizeName=strName; };
    10.  
    11.     inline const qreal merchandizePrice()
    12.         { return m_OrderValues.rMerchandizePrice; };
    13.     inline void setMerchandizePrice(qreal rPrice)
    14.         { m_OrderValues.rMerchandizePrice=rPrice; };
    15.  
    16.     inline const qint16 merchandizeQuantity()
    17.         { return m_OrderValues.iMerchandizeQuantity; };
    18.     inline void setMerchandizeQuantity(qint16 iQuantity)
    19.         { m_OrderValues.iMerchandizeQuantity=iQuantity; };
    20.  
    21.     inline const qreal merchandizeSubtotal()
    22.         { return m_OrderValues.rSubtotal; };
    23.     inline void setSubtotal(qreal rSubtotal)
    24.         { m_OrderValues.rSubtotal=rSubtotal; };
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    I simply do not get it ...
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  4. 22nd May 2008, 18:06 #4
    jpn
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    Default Re: class operator problem

    They return const values but the methods itself are not const.
    J-P Nurmi
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  5. 22nd May 2008, 18:12 #5
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    Default Re: class operator problem

    How do I make them const? If I write for instance:
    Qt Code: 
    1. inline const qint16 merchandizeID()
    2.         { return m_OrderValues.iMerchandizeID; } const;
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    I get this error:
    Qt Code: 
    1. mingw32-make 
    2. mingw32-make -f Makefile.Debug
    3. mingw32-make[1]: Entering directory `C:/Documents and Settings/markofr/workspace/Client'
    4. g++ -c -g -frtti -fexceptions -mthreads -Wall -DUNICODE -DQT_LARGEFILE_SUPPORT -DQT_DLL -DQT_SQL_LIB -DQT_GUI_LIB -DQT_CORE_LIB -DQT_THREAD_SUPPORT -DQT_NEEDS_QMAIN -I"..\..\..\..\Qt\4.4.0\include\QtCore" -I"..\..\..\..\Qt\4.4.0\include\QtCore" -I"..\..\..\..\Qt\4.4.0\include\QtGui" -I"..\..\..\..\Qt\4.4.0\include\QtGui" -I"..\..\..\..\Qt\4.4.0\include\QtSql" -I"..\..\..\..\Qt\4.4.0\include\QtSql" -I"..\..\..\..\Qt\4.4.0\include" -I"c:\Qt\4.4.0\include\ActiveQt" -I"debug" -I"." -I"..\..\..\..\Qt\4.4.0\mkspecs\win32-g++" -o debug\CShoppingCartModel.o CShoppingCartModel.cpp
    5. In file included from CShoppingCartModel.h:9,
    6.                  from CShoppingCartModel.cpp:1:
    7. CMerchandizeOrder.h:20: error: declaration does not declare anything
    8. mingw32-make[1]: *** [debug/CShoppingCartModel.o] Error 1
    9. mingw32-make[1]: Leaving directory `C:/Documents and Settings/markofr/workspace/Client'
    10. mingw32-make: *** [debug] Error 2
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  6. 22nd May 2008, 18:13 #6
    jpn
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    Default Re: class operator problem

    Const-correctness
    J-P Nurmi
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  7. 22nd May 2008, 19:13 #7
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    Default Re: class operator problem

    Qt Code: 
    1. inline const qint16 merchandizeID() const 
    2.         { return m_OrderValues.iMerchandizeID; }
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    A camel can go 14 days without drink,
    I can't!!!
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