could anybody please explain to me how come this happen?
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void fun(CArray) { } void fun(CArray& ) { } why dose the argument in the first function produce a error(like this: error C2664: 'fun' : cannot convert parameter 1 from 'class CArray' to 'class CArray'No copy constructor available for class 'CArray') while the second funtion is right? Thank you very much!!!
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void fun(CArray) { } void fun(CArray& ) { } why dose the argument in the first function produce a error(like this: error C2664: 'fun' : cannot convert parameter 1 from 'class CArray' to 'class CArray'No copy constructor available for class 'CArray') while the second funtion is right? Thank you very much!!!
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void fun(CArray) { } void fun(CArray& ) { } why dose the argument in the first function produce a error(like this: error C2664: 'fun' : cannot convert parameter 1 from 'class CArray' to 'class CArray'No copy constructor available for class 'CArray') while the second funtion is right? Thank you very much!!!
I've got you these from MSDN i think you will understand why? let me know in case not SYMPTOMS When a user-defined class contains a CArray and the same user-defined class is nested in another class, you may get the following errors if no copy constructor and assignment operator are provided for the class: main.cpp(52): error C2664: 'Add' : cannot convert parameter 1 from 'class B' to 'class B' No copy constructor available for class 'B' After adding a copy constructor, you get the following error message: afxtempl.h(443): error C2582:'B' : 'operator =' function is unavailable afxtempl.h(1566):while compiling class-template member function 'void __thiscall CArray::SetAtGrow(int,class B)' CAUSE If the class that contains a CArray is nested in another class, then its objects must be copied. The compiler does not construct an implicit copy constructor and copy assignment operator because the class in question has CArray as a member, which does not have a copy constructor and copy assignment operator, and CArray inherits from CObject, which has a protected copy construtor and a copy assignment operator. The compiler tries to generate the implicit ones, but that generates a call to CObject's version of them. Because they are protected, the above errors are generated. RESOLUTION You need to provide a copy constructor and an assignment operator for the class. STATUS Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was corrected in Microsoft Visual C++ .NET. MORE INFORMATION The following example shows the correct use of the CArray class: // No compiler option needed. #include struct A { int i; int j; }; class B { public: B(); ~B(); // Need to define copy ctor and assignment operator. B(const B& b){ // Your copy ctor body goes here. } /* const B& */ void operator= (const B& b) { // Your assignment operator body goes here. } protected: CArray arrayA; }; B::B(){} B::~B(){} class C { public: C(); ~C(); void addElement(); protected: CArray arrayB; }; C::C(){} C::~C(){} void C::addElement() { B temp; arrayB.Add(temp); } void main() { } I've been programming since year 1999, graduated from Univeristy Paris 2 France, fluent in C,C++,VC++,Web programming (XML,HTML,php etc..),.NET frameworks,C# and ASP.NET,SQL server, Mastering VC++ .NET and SQL server,data structure
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void fun(CArray) { } void fun(CArray& ) { } why dose the argument in the first function produce a error(like this: error C2664: 'fun' : cannot convert parameter 1 from 'class CArray' to 'class CArray'No copy constructor available for class 'CArray') while the second funtion is right? Thank you very much!!!
The first one you are passing by value. So a copy constructor is required. The second one you are passing by reference so no copy constructor is required. Only the reference is passed.
Jesus Loves You and Me :)
--Owner Drawn --Nothing special --Defeat is temporary but surrender is permanent --Never say quits --Jesus is Lord
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I've got you these from MSDN i think you will understand why? let me know in case not SYMPTOMS When a user-defined class contains a CArray and the same user-defined class is nested in another class, you may get the following errors if no copy constructor and assignment operator are provided for the class: main.cpp(52): error C2664: 'Add' : cannot convert parameter 1 from 'class B' to 'class B' No copy constructor available for class 'B' After adding a copy constructor, you get the following error message: afxtempl.h(443): error C2582:'B' : 'operator =' function is unavailable afxtempl.h(1566):while compiling class-template member function 'void __thiscall CArray::SetAtGrow(int,class B)' CAUSE If the class that contains a CArray is nested in another class, then its objects must be copied. The compiler does not construct an implicit copy constructor and copy assignment operator because the class in question has CArray as a member, which does not have a copy constructor and copy assignment operator, and CArray inherits from CObject, which has a protected copy construtor and a copy assignment operator. The compiler tries to generate the implicit ones, but that generates a call to CObject's version of them. Because they are protected, the above errors are generated. RESOLUTION You need to provide a copy constructor and an assignment operator for the class. STATUS Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was corrected in Microsoft Visual C++ .NET. MORE INFORMATION The following example shows the correct use of the CArray class: // No compiler option needed. #include struct A { int i; int j; }; class B { public: B(); ~B(); // Need to define copy ctor and assignment operator. B(const B& b){ // Your copy ctor body goes here. } /* const B& */ void operator= (const B& b) { // Your assignment operator body goes here. } protected: CArray arrayA; }; B::B(){} B::~B(){} class C { public: C(); ~C(); void addElement(); protected: CArray arrayB; }; C::C(){} C::~C(){} void C::addElement() { B temp; arrayB.Add(temp); } void main() { } I've been programming since year 1999, graduated from Univeristy Paris 2 France, fluent in C,C++,VC++,Web programming (XML,HTML,php etc..),.NET frameworks,C# and ASP.NET,SQL server, Mastering VC++ .NET and SQL server,data structure
I got it,thank you very much. I am a beginner of programming, I found that a lot of people like you can always find answers to questions quickly and correctly from on the Internet especially microsoft's web site. could you please tell me how you do that ? is there relatively any way to follow? or is any books or articles teaching these things you can recommend to me? Thank you again!! ------------------- I am learning C++ and English
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The first one you are passing by value. So a copy constructor is required. The second one you are passing by reference so no copy constructor is required. Only the reference is passed.
Jesus Loves You and Me :)
--Owner Drawn --Nothing special --Defeat is temporary but surrender is permanent --Never say quits --Jesus is Lord
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I got it,thank you very much. I am a beginner of programming, I found that a lot of people like you can always find answers to questions quickly and correctly from on the Internet especially microsoft's web site. could you please tell me how you do that ? is there relatively any way to follow? or is any books or articles teaching these things you can recommend to me? Thank you again!! ------------------- I am learning C++ and English
Dear, you can visit microsft.msdn.com, that is full of help, or simply use MSDN help that comes with Visual studio 6.0 ,2003 or 2005, just search for the error number and the whole help will be yours serving your needs, I was using C++ for 7 years, trust me go for C# and never for J#. C# is easier, has the same libraries and more rich GUI wise. I've been programming since year 1999, graduated from Univeristy Paris 2 France, fluent in C,C++,VC++,Web programming (XML,HTML,php etc..),.NET frameworks,C# and ASP.NET,SQL server, Mastering VC++ .NET and SQL server,data structure and database design
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Dear, you can visit microsft.msdn.com, that is full of help, or simply use MSDN help that comes with Visual studio 6.0 ,2003 or 2005, just search for the error number and the whole help will be yours serving your needs, I was using C++ for 7 years, trust me go for C# and never for J#. C# is easier, has the same libraries and more rich GUI wise. I've been programming since year 1999, graduated from Univeristy Paris 2 France, fluent in C,C++,VC++,Web programming (XML,HTML,php etc..),.NET frameworks,C# and ASP.NET,SQL server, Mastering VC++ .NET and SQL server,data structure and database design