Go4Expert - Why this code is not working?

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- - Why this code is not working? (http://www.go4expert.com/showthread.php?t=17329)

Why this code is not working?

CASE 1: Following code is not working...saying
error: `int Base::j' is protected
error: within this context

Code:

#include<iostream.h>



class Base

{

public:

  Base() { i=10; j=20;}

  int i;

protected:

  int j;

};



class Derived : public Base

{

public:

  Derived() { k=30;}

  int k;

void fun(Base);

};



void Derived :: fun(Base b)

{

  b.i=100;

  b.j=200;   //Problem is here...

}



int main()

{

  Base Bobj;

  Derived Dobj;

  Dobj.fun(Bobj);

      

  return 0;

}

CASE 2: This code works fine...This is reasonable...

Code:

#include<iostream.h>



class Base

{

public:

  Base() { i=10; j=20;}

  int i;

protected:

  int j;

};



class Derived : public Base

{

public:

  Derived() { k=30;}

  int k;

void fun(Base);

};



void Derived :: fun(Base b)

{

  b.i=100;

  this->j =200;

  //b.j=200;

}



int main()

{

  Base Bobj;

  Derived Dobj;

  Dobj.fun(Bobj);

      

  return 0;

}

But in case 1, i think compilation error should not come, because protected member is accesing by derived function only.

Re: Why this code is not working?

In base calss j is protected member. In case 1 you are trying to assign value for a protected member . so it failed.
Where as in case 2, you used 'this' means derived class object. When a derived class object is created internally it will create base class object too . Since j is protected it is accessible by the derived class..
So you can assign the value. Where as in case 1 Base b is a different object, so you can't access the protected variable.