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List:       kde-devel
Subject:    Re: accessing protected members of a parent class
From:       Patrick Julien <freak () ideasandassociates ! com>
Date:       2002-04-04 18:34:00
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Ellis Whitehead wrote:
> On Thursday 04 April 2002 11:40, Patrick Julien wrote:
> 
>>you have to make B a friend in the protected or private section of class A.
> 
> 
> That is in fact what I've been doing to get around the problem.  But its 
> ugliness quotient is horrendous and you can only use this approach for 
> sub-classes which you program yourself -- leaving the option unavailable to 
> programmers using the library...

I agree:).  How about ...

class A {
protected:
	void access_link(A* a) {a->link();}//Access_link is not virtual
	virtual void link(A* a) {/*...*/}
};

class B : public A {
protected:
	virtual void link(A* a) { access_link(a); /*...*/ }
};

Now, if you really want to get creative (or ugly depending on how you 
see it:) have access_link return a pointer to the link method, then you 
can use it from B::link().


> 
> 
> 
>>Ellis Whitehead wrote:
>>
>>>Is it possible to access protected members in an object whose type is a
>>>superclass of the current method's class?  Somehow in over ten years of
>>>C++ programming, I've missed or forgotten the fact that this isn't
>>>allowed. :(
>>>
>>>Compiling the following code, for example, results in the following
>>>error:
>>>
>>>$ g++ test.cpp -o test.o
>>>test.cpp: In method `void B::link(A *)':
>>>test.cpp:4: `void A::link(A *)' is protected
>>>test.cpp:15: within this context
>>>
>>>
>>>class A
>>>{
>>> protected:
>>>	virtual void link( A* );
>>>};
>>>
>>>class B : public A
>>>{
>>> protected:
>>>	virtual void link( A* );
>>>};
>>>
>>>void B::link( A* a )
>>>{
>>>	a->link( 0 );	// *** fails ***
>>>}
>>>
>>>
>>>>>Visit http://mail.kde.org/mailman/listinfo/kde-devel#unsub to
>>>>>unsubscribe <<
>>>>
> 
>  
> 
>>>Visit http://mail.kde.org/mailman/listinfo/kde-devel#unsub to unsubscribe <<
>>


-- 
Patrick Julien
Ideas & Associates
(514) 940-2891x211

 
>> Visit http://mail.kde.org/mailman/listinfo/kde-devel#unsub to unsubscribe <<
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