const iterator

Hi,

I have a problem with a constant iterator. This is an example of the situation

class B
{
public:
B(){}

std::list<int> m_List;
std::list<int>::iterator Iter;


const int Func ( ) const
{
std::list<int>::iterator IterFunc;
IterFunc = m_List.begin ( );
return 2;
}
};


int main ( )
{
B ObjB;
ObjB.Func ( );

return 0;
}

I have this compilation error

error C2679: binary '=' : no operator found which takes a right-hand operand of type 'std::list<_Ty>::_Const_iterator<_Secure_validation>' (or there is no acceptable conversion)

If I remove the const at the end of Func it solves the problem but I need this function to be const. How I can solve this problem

Thank you

Code:

---

const int Func ( ) const
{
std::list<int>::const_iterator IterFunc;
IterFunc = m_List.begin ( );
return 2;
}

---

Perfect, Thank you for your answer

Quote:

---

Originally Posted by Geof

Hi,

I have a problem with a constant iterator. This is an example of the situation

class B
{
public:
B(){}

std::list<int> m_List;
std::list<int>::iterator Iter;


const int Func ( ) const
{
std::list<int>::iterator IterFunc;
IterFunc = m_List.begin ( );
return 2;
}
};


int main ( )
{
B ObjB;
ObjB.Func ( );

return 0;
}

I have this compilation error

error C2679: binary '=' : no operator found which takes a right-hand operand of type 'std::list<_Ty>::_Const_iterator<_Secure_validation>' (or there is no acceptable conversion)

If I remove the const at the end of Func it solves the problem but I need this function to be const. How I can solve this problem

Thank you

---

Func is const, that means inside Func, all member variables are const, including m_list. When you call begin on m_list, you are calling the const version of begin, which returns a const iterator.

You cannot assign a const_iterator to an iterator, because that would break const correctness,

If you are not planning to use iterfunc to modify you list, then declare it const_iterator. If you ARE planning to use it to modify your list, then don't call Func const, since it isn't.

You should know that constness IS part of function signatures. Writing:

Code:

---

myList.begin()

---

could call two different functions depending on your list constness:

Code:

---

iterator begin(); //non const version, returning a non const iterator
const_iterator begin() const; //const version returning a const_iterator

---

Your compiler will always try to use non-const functions if your object is not const, and const functions if your object is const.