Re: again the problem: the destructor is called twice

From:
"mlimber" <mlimber@gmail.com>
Newsgroups:
comp.lang.c++
Date:
23 Mar 2007 08:23:01 -0700
Message-ID:
<1174663381.538143.160630@n76g2000hsh.googlegroups.com>
On Mar 23, 11:15 am, "David" <clam...@gmail.com> wrote:

Hi all,

I posted my question two days ago, and tried to solve this problem.
but until now I didn't solve that. and I cut my codes so maybe this
time it is more readable.

/////////////////////////////////////////////////////
#ifndef MYCLASS_H_
#define MYCLASS_H_

#include <string>
#include <list>
//#include "name.h"

using namespace std;
class myclass
{
protected:
        list<string> namelist;
// map<int,vector<name> >names;
public:

        myclass();
        myclass(const myclass &my);
        ~myclass();
// myclass& operator=(const myclass &it);
        void AddName(const string &name);
        void GetMyclass();

};

#endif

///////////////////////////////////////////////
myclass.cpp
#include "myclass.h"
#include <algorithm>
#include <iostream>

myclass::myclass()
{

}

myclass::myclass(const myclass &my)
{

        namelist=my.namelist;

}

myclass::~myclass()
{

        namelist.erase(namelist.begin(),namelist.end());

}

void myclass::AddName(const string &name)
{
        list<string>::iterator ii;
        ii=find(namelist.begin(),namelist.end(),name);

        if(ii==namelist.end())
                namelist.push_back(name);

}

void myclass::GetMyclass()
{
        list<string>::iterator ii;
        for(ii=namelist.begin();ii!=namelist.end();ii++)
                cout<<*ii<<endl;

}

/////////////////////////////////////////////////
test.h
#ifndef TEST_H_
#define TEST_H_

#include <string>
#include <map>
#include "myclass.h"

using namespace std;

class test
{
protected:
        map<string,myclass*> tests;

public:
        test();
        test(const test& mytest);
        test& operator=(const test& ts);
        ~test();
        void AddMyclass(const string &name,const myclass &my);
        void GetTest();

};

#endif

////////////////////////////////////////////////////
test.cpp

#include "test.h"

#include <utility>
#include <iostream>

test::test()
{}

test::test(const test& mytest)
{
        tests=mytest.tests;

}

test& test::operator =(const test &ts)
{
        if(this!=&ts)
        {
                map<string,myclass*>::iterator ii;
                for(ii=tests.begin();ii!=tests.end();++ii)
                        delete(ii->second);
                tests.clear();

                tests=ts.tests;
        }
        return *this;

}

test::~test()
{
        map<string,myclass*>::iterator ii;
        for(ii=tests.begin();ii!=tests.end();++ii)
                delete(ii->second);
        tests.clear();}

void test::AddMyclass(const string &name,const myclass &my)
{
        map<string,myclass*>::iterator ii;
        myclass* newmyclass=NULL;

        ii=tests.find(name);
        if(ii==tests.end())
        {
                newmyclass=new myclass(my);
                tests[name]=newmyclass;
        }

}

void test::GetTest()
{
        map<string,myclass*>::iterator ii;
        for(ii=tests.begin();ii!=tests.end();ii++)
        {
                cout<<"the name is:"<<ii->first<<endl;
                ii->second->GetMyclass();
        }

}

////////////////////////////////////////////////////////////////////
call.h

#ifndef CALL_H_
#define CALL_H_

#include "test.h"

class call
{
public:
        inline void SetTest(const test& ts){testagain=ts;}


Here you make a copy of test. There are now two objects in existence,
so two destructors will be called at some point.

protected:
        test testagain;};

#endif

///////////////////////////////////////////////////////////////////
main
#include "myclass.h"
#include "test.h"
#include "call.h"

int main()
{
        test tt;
        myclass my;
        string ss[3]={"a","b","c"};
        call ca;

        for(int i=0;i<3;i++)
                my.AddName(ss[i]);

        my.GetMyclass();

        tt.AddMyclass("my class",my);

        tt.GetTest();

        ca.SetTest(tt);
        return 0;

}

The problem is at the line ca.SetTest(tt). Could somebody tell me how
to solve it? Thanks.


You could pass ownership of the test object rather than making a copy.
One way to do that is to use std::auto_ptr, which signifies unique
ownership. So if your "call" class accepts an auto_ptr<test>, the
implicit understanding is that it takes sole ownership of that object.

Cheers! --M

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