I am coding a vector class with iterators for a school exercice. I am getting the following error and I don't know how to go about it:
'no suitable user-defined conversion from "vectorIterator" to "vectorIterator<const int>" exists'
This is the code I am trying to execute:
vector<int> v;
v.push_back(1);
v.push_back(2);
vector<int>::const_iterator it = v.begin();
This is part of the code in my class vector:
template <typename T, typename Alloc = std::allocator<T> >
class vector {
..
public:
typedef vectorIterator<value_type> iterator;
typedef vectorIterator<const value_type> const_iterator;
..
iterator begin() { return iterator(m_data); } // if commented the above code works
const_iterator begin() const { return const_iterator(m_data); }
..
}
If I comment the first form of begin() the code compiles and runs ok, so it seems that it obscures the const form. I would expect the compiler to know to use the const form of begin(), but it does not. What am I missing?
Thanks a lot
Since vectorIterator is a template class, which means that vectorIterator<int> and vectorIterator<const int> are two different types, they can not be converted to each other. You need to add a conversion constructor for vectorIterator<const int> that accepts vectorIterator<int>, using template should be enough (some constraints on U are omitted here for simplicity):
template<typename T>
struct vectorIterator {
// ...
template<typename U>
vectorIterator(vectorIterator<U>);
};