Re: Can someone explain how these operator is suppose to work

From:

"Alex Blekhman" <xfkt@oohay.moc>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 23 May 2007 12:13:08 +0300

Message-ID:

<#4e3upRnHHA.3872@TK2MSFTNGP04.phx.gbl>

"Anders Eriksson" wrote:

Hello,

I'm using a 3:rd party library and in one class I have a
protected variable
that I need to get.

I see that the creator of the class has two operators that
seem to be the
trick to get the value but I don't get how to use the
operators.

The class looks like this

Class CYObject
{
protected:
xObject* m_pObject;
// a number of other variables...
public:
xObject& operator*(){ return *m_pObject;}
xObject* operator->(){ return m_pObject;}
}

If I have an instance of CYObject called myObject how do I
get the
myObject->m_pObject??

You are not supposed to be able. It seems that `CYObject' is
some sort of smart pointer. The purpose of smart pointer is
to encapsulate real pointer and at the same time to privde
pointer-like semantics. So, instead of using pointer to
`xObject' you use instance of `CYObject' as if it was real
pointer:

CYObject ptrObj(...);

ptrObj->Foo(); // xObject::Foo is called
xObject& xObj = *ptrObj;
....

Usually smart pointer classes provide a method to get
encapsulated pointer for rare cases when you need real
pointer. For example,

xObject* CYObject::GetPtr()
{
return m_pObject;
}

So, when you need to access encapsulated pointer, then you
should state it explicitly:

void Bar(xObject* p);
....
Bar(ptrObj.GetPtr()); // beware!

Alex