MFC structure array

Question

I would like to create an array of structure in C++. I do not know the size so I would like to make it dynamic. I have tried with CList but I have failed. So I tried using a vector but I have the same error.

I have the following structure in my header :

typedef CArray<CArray<double, double>,double> ObjectArray;
struct MyStruct {
  CString type;
  CString name;
  ObjectArray value;
};
std::vector<MyStruct> ST;

In my cpp file, I have the following code to populate my array. STR is a structure I populated beforehand.

ST.push_back(STR);

I have the following error when building:

c:\program files (x86)\microsoft visual studio 10.0\vc\atlmfc\include\afxtempl.h(262): error C2248: 'CObject::CObject' : cannot access private member declared in class 'CObject

I guess I am doing something wrong but I do not understand what I am missing.

probably the copy-constructor is private, but nothing can be said by seeing your code. — Rakib
– Rakib, Commented May 30, 2014 at 8:51

PaulMcKenzie · Accepted Answer · 2014-05-30 09:22:28Z

2

Instead of mixing MFC containers with STL containers, why not use std::vector throughout?

#include <vector>
typedef std::vector<std::vector<double> > ObjectArray;
struct MyStruct {
    CString type;
    CString name;
    ObjectArray value;
};

std::vector<MyStruct> ST;

The CString is OK (CString has its uses, and is also copyable). However in this day and age, using the MFC containers instead of STL containers is rarely, if ever necessary. I have read that even Microsoft doesn't use them anymore in their C++ based programs and now only use the STL containers.

edited May 30, 2014 at 9:22

answered May 30, 2014 at 9:17

PaulMcKenzie

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1 Comment

oro777 Over a year ago

Thank you very much. As everybody said the mixture MFC/STL is the source of the error. By replacing my ObjectArray with a STL container, I have no error anymore. I will try to stick to the STL container in the future.

JohnB · Accepted Answer · 2014-05-30 09:15:39Z

If you derive a class from CObject, you have to provide a custom copy constructor, see here:

http://msdn.microsoft.com/en-us/library/st9cdfkz.aspx

"The standard C++ default class copy constructor does a member-by-member copy. The presence of the private CObject copy constructor guarantees a compiler error message if the copy constructor of your class is needed but not available. You must therefore provide a copy constructor if your class requires this capability."

I guess CArray inside the struct generates the problem, as it is derived from CObject and does not define a custom copy constructor, see here:

http://msdn.microsoft.com/en-us/library/4h2f09ct.aspx

Either don't use it, or derive some CDerivedArray from CArray and define a custom copy constructor there.

Why don't you use std::vector or std::map or another STL class rather than CArray?

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