What does this statement return?

Question

Suppose I have a class like this:

class Owner
{
private:
    long m_Id;
    QString m_Name;

public:
    Owner() : m_Id(0) { ; }
    virtual ~Owner() { ; }

    inline long id() const { return m_Id; }
    inline void setId(long id) { m_Id = id; }

    inline const QString & name() const { return m_Name; }
    inline void setName(const QString & name) { m_Name = name; }
}

I saw a code &Owner::m_Id;. I'm confused, does it return a pointer to the member? and if so, how can it be used on Owner's instances?

Could you provide some context to the usage of the `&Owner::m_Id`? — soulmerge, Mar 28 '12 at 12:37
possible duplicate of [C++, function pointer to member function](http://stackoverflow.com/questions/2402579/c-function-pointer-to-member-function) — Mike DeSimone, Mar 28 '12 at 12:41
@MikeDeSimone `m_Id` is not a function, so that's not a duplicate. — Luchian Grigore, Mar 28 '12 at 12:45

score 4 · Accepted Answer · answered Mar 28 '12 at 12:46

4

It does return a member pointer. You can use it to access m_Id indirectly, as follows:

long Owner::* ptrMem = &Owner::m_Id;
Owner owner;
owner.*ptrMem = 10;
cout << owner.m_Id << endl;

This code works in a context where m_Id is accessible, for example in a member function.

This example is not too interesting, because your class does not have other members of type long. In situations where multiple such members exist, member pointers become more valuable: you can postpone the binding to a particular member to run-time.

answered Mar 28 '12 at 12:46

Sergey Kalinichenko

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Thank you very much, that was what I wanted to hear.Don't understand why so many downvotes :( – Davita Mar 28 '12 at 12:47
@Davita "Don't understand why so many downvotes" neither do I - I think it's a valid question, so I upvoted it. – Sergey Kalinichenko Mar 28 '12 at 12:49

What does this statement return?

1 Answers1