CODEWITHSUNDEEP
c++mfc
zar
zar

Reputation: 12237

Passing a reference to a variable

I get an error stack around variable dlgFile is corrupted which I am trying to fix. This is legacy code and it looks dubious. I replaced part of in another project which is here:

void CPlantDlg::OnBnClickedButtonTestReference()
{
    CString str = _T("Hello string");

    { // intentional so destructor of Tester is called below
        Tester tester( str );
    }

    AfxMessageBox (str );
}

The Tester class is:

class Tester
{
public:
    Tester(CString & str);
    ~Tester(void);

    CString _str;
};

Tester::Tester(CString & str) : _str( str )
{

}

Tester::~Tester(void)
{
    //_str = "Changed"; // say I do this, what will be printed in caller function?
}

Is passing of the CString safe this way? I think the Tester class should destroy its _str which should result in getting the original str destroyed outside the class?

When I run it does prompt "Hello String" though.

If I enable _str = "Changed" what will you expect to prompt? It actually still shows the original string. It was passed by reference, why is that?

Upvotes: 0

Views: 89

Answers (1)

Kik
Kik

Reputation: 428

The _str variable in your Tester class is an instance of a CString object. When the member initializer says

_str( str )

it is not storing a reference to the CString reference that is passed to the constructor, the copy constructor is being called, and _str is initialized with the same value as str. It is just a copy. So changing it will not have an effect on the original CString.

Upvotes: 3

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