Vector - using iterator vs index

Question

I am relatively new to C++,

I have two pieces of code:

for (std::vector<int>::size_type i = 0; i != inventoryvec.size(); i++)
{
    cout << inventoryvec[i].description << endl;
}

and

    for (std::vector<items>::iterator it = inventoryvec.begin(); it != inventoryvec.end(); ++it) 
    {
        cout << inventoryvec[it].description;
    }

The second code is not valid "Error no operator "[]" matches these operands" - why am I unabled to use "it" in the same way I use "i". It main purpose it to represent a value right?

Is this a limitation of using the iterator over indices or am I just doing something wrong.

Answer 1

To dereference a vector use the * operator.

Replace inventoryvec[it] with (*it) .

Of course, like usual, you can use it->description as shorthand for (*it).description .

Answer 2

Iterators are just abstract pointers. An iterator points to a member. You dereference it with * (or you can use use -> ), advance it with ++ , and move it one item back (if that operation is implemented) with -- .

In the case of vectors, there's virtually no abstraction. Vector iterators are (or can be) (with the exception of specializations) literally pointers to the members of the array that std::vector wraps.

Answer 3

You can think of std::vector<items>::iterator as a pointer of items type but more complicated. Thus, you use the dereference operator (aka *) to access the data to which it points. You can use -> operator as well