How to get data out of the STL's const_iterator?

Question

I have something that runs like this:

T baseline;
list<T>::const_iterator it = mylist.begin();
while (it != mylist.end()) {
    if (it == baseline) /* <----- This is what I want to make happen */
    // do stuff
}

My problem is that I have no idea how to extract the data from the iterator. I feel like this is a stupid thing to be confused about, but I have no idea how to do it.

EDIT : Fixed begin.end()

Answer 1

Iterators have an interface that "looks" like a pointer (but they are not necessarily pointers, so don't take this metaphor too far).

An iterator represents a reference to a single piece of data in a container. What you want is to access the contents of the container at the position designated by the iterator. You can access the contents at position it using *it. Similarly, you can call methods on the contents at position it (if the contents are an object) using it->method().

This doesn't really relate to your question, but it is a common mistake to be on the lookout for (even I still make it from time to time): If the contents at position it are a pointer to an object, to call methods on the object, the syntax is (*it)->method(), since there are two levels of indirection.

Answer 2

The syntax to use an iterator is basically the same as with a pointer. To get the value the iterator "points to" you can use dereferencing with *:

 if (*it == baseline) ...

If the list is a list of objects you can also access methods and properties of the objects with ->:

 if (it->someValue == baseline) ...