Remove code duplication for virtual class members

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I have got myself into a strange issue now. Ill write a really simplified version of the same.

C++

class Base
{
public:
virtual int func1()=0;
virtual int func2()=0;
protected:
int n;
};

class der1: public Base
{
//implements the virtual functions of the base and uses the protected data members of the base.
};

class der2: public Base
{
//implements the virtual functions of the base and uses the protected data members of the base.
}

Now the problem.... both der1 and der2 implements the virtual functions of base pretty much the same way. But some other classes (der3, der4) has their own implementations. But still need to inherit from base.
How do i refactor the code to remove the code duplication in an oop manner?

What I have tried:

I don't want a function to have the common code and then from the der1 and der2 to call it. That won't be possible unless I send all the protected variables of base to it as an argument. Didn't quite like the approach.
So, looking for a OOP approach to handle this problem,

Posted 20-Oct-18 23:12pm

_PitrakSarkar_

Updated 20-Oct-18 23:25pm

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Rick York 21-Oct-18 18:31pm

"That won't be possible unless I send all the protected variables of base to it as an argument." This is not true. If you do as Mr. Griff suggests, Intermediate provides a default implementation and nothing else has to implement func1 and func2 unless you want differing behavior. Also, Intermediate will have access to all public and protected members and methods of Base.

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OriginalGriff · Accepted Answer · 2018-10-20T23:25:00

Solution 1

Derive a third class from Base which handles the "common" implementation:

C++

class Intermediate: public Base
   {
   ...
   }

Then derive your classes from that:

class der1: public Intermediate
   { 
   ...
   };

class der2: public Intermediate
   {
   ...
   }

Posted 20-Oct-18 23:25pm

OriginalGriff

Comments

_PitrakSarkar_ 21-Oct-18 5:33am

the problem with this solution I feel is, now intermediate has to implement the pure virtual functions of Base and again, der1 and der2 also have to implement the same. Is there a better way?

OriginalGriff 21-Oct-18 5:39am

No, Intermediate provides concrete implementations, which are inherited by der1 and der2