Multi-level inheritance and accessing base protected member variables

[Joseph Paterson]

Hi all,

I'm having some trouble with the following code (simplified to show
the problem)

class Counter
{
protected:
int m_counter;
}

template <class K, class V>
class IMap : public Counter
{
// Virtual function declarations
}

template <class K, class V>
class HashMap : public IMap<K, V>
{
// Implementation of the virtual functions declared in IMap
}

Now when I'm implementing the functions in the HashMap class, I can't
seem to access the m_counter member variable by just using m_counter
(I get an undeclared reference from GCC), but when I use this-

>m_counter, then it works fine.

Could anybody help me out with this one?

Thanks,

Joseph Paterson.

[Hari]

Joseph Paterson je napisao:

Hi all,

I'm having some trouble with the following code (simplified to show
the problem)

class Counter
{
protected:
int m_counter;
}

template <class K, class V>
class IMap : public Counter
{
// Virtual function declarations
}

template <class K, class V>
class HashMap : public IMap<K, V>
{
// Implementation of the virtual functions declared in IMap
}

Now when I'm implementing the functions in the HashMap class, I can't
seem to access the m_counter member variable by just using m_counter
(I get an undeclared reference from GCC), but when I use this-

m_counter, then it works fine.

Could anybody help me out with this one?

Thanks,

Joseph Paterson.

If you exclude some errors (like missing ; at end of class or using
class instead of typename) I do not
see what is wrong, here is code that compiles without errors (on MINGW
and VC8):

class Counter
{
protected:
int m_counter;

};

template <typename K, typename V>
class IMap : public Counter
{
public:
IMap() {}

virtual void foo() = 0;

};

template <typename K, typename V>
class HashMap : public IMap<K, V>
{
public:
HashMap() {}

void foo() {
m_counter = 10;
}

} ;

int main()
{
HashMap<int, inta;
a.foo();
}

P.S.
You can always test code on multiple compilers at http://dinkumware.com/exam/
..

Best,
Pasalic Zaharije

[Sumit Rajan]

Joseph Paterson wrote:

Hi all,

I'm having some trouble with the following code (simplified to show
the problem)

class Counter
{
protected:
int m_counter;
}

template <class K, class V>
class IMap : public Counter
{
// Virtual function declarations
}

template <class K, class V>
class HashMap : public IMap<K, V>
{
// Implementation of the virtual functions declared in IMap
}

Now when I'm implementing the functions in the HashMap class, I can't
seem to access the m_counter member variable by just using m_counter
(I get an undeclared reference from GCC), but when I use this-

>m_counter, then it works fine.

Could anybody help me out with this one?

How about using this->m_counter instead of "just using" m_counter? Does
that fix your problem?


--
Sumit Rajan <su*********@gmail.com>

[Sumit Rajan]

Hari wrote:

Joseph Paterson je napisao:

>Hi all,

I'm having some trouble with the following code (simplified to show
the problem)

class Counter
{
protected:
int m_counter;
}

template <class K, class V>
class IMap : public Counter
{

Path: uni-berlin.de!fu-berlin.de!postnews.google.com!q69g2000hsb.googlegr oups.com!not-for-mail
From: Hari <pa**************@gmail.com>
Newsgroups: comp.lang.c++
Subject: Re: Multi-level inheritance and accessing base protected member variables
Date: Thu, 28 Jun 2007 01:27:16 -0700
Organization: http://groups.google.com
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References: <11**********************@m36g2000hse.googlegroups .com>
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Xref: uni-berlin.de comp.lang.c++:977090
Joseph Paterson je napisao:

>Hi all,

I'm having some trouble with the following code (simplified to show
the problem)

class Counter
{
protected:
int m_counter;
}

template <class K, class V>
class IMap : public Counter
{
// Virtual function declarations
}

template <class K, class V>
class HashMap : public IMap<K, V>
{
// Implementation of the virtual functions declared in IMap
}

Now when I'm implementing the functions in the HashMap class, I can't
seem to access the m_counter member variable by just using m_counter
(I get an undeclared reference from GCC), but when I use this-

>>m_counter, then it works fine.

Could anybody help me out with this one?

Thanks,

Joseph Paterson.

If you exclude some errors (like missing ; at end of class or using
class instead of typename) I do not
see what is wrong, here is code that compiles without errors (on MINGW
and VC8):

class Counter
{
protected:
int m_counter;

};

template <typename K, typename V>
class IMap : public Counter
{
public:
IMap() {}

virtual void foo() = 0;

};

template <typename K, typename V>
class HashMap : public IMap<K, V>
{
public:
HashMap() {}

void foo() {
m_counter = 10;

this->m_counter = 10;

See:
http://www.parashift.com/c++-faq-lit...html#faq-35.19

}

} ;

int main()
{
HashMap<int, inta;
a.foo();
}

P.S.
You can always test code on multiple compilers at http://dinkumware.com/exam/
..

Best,
Pasalic Zaharije

Regards,
Sumit.

--
Sumit Rajan <su*********@gmail.com>

[Joseph Paterson]

Exactly what I needed, thanks!
Apologies for omitting the ';' at the end of the class declarations!

Joseph Paterson.