Implementing a custom C++ iterator type

For my own reference, and possibly others’, here’s a cookbook example of a custom C++ iterator type to use when the implementation details of a particular container is unimportant and the normal C++ algorithms should be used on iterator begin and end ranges.

class custom_iterator : public std::iterator<std::input_iterator_tag, exposed_type>
{
public:

    custom_iterator(something_that_initializes_the_type_exposer& initializer)
        : exposer_(initializer)
    {
    }

    reference operator*()
    {
        return exposer_.ref();
    }

    const reference operator*() const
    {
        return exposer_.ref();
    }

    pointer operator->()
    {
        return exposer_.ptr();
    }

    const pointer operator->() const
    {
        return exposer_.ptr();
    }

    custom_iterator& operator++()
    {
        ++it_;

        return *this;
    }

    bool operator==(const custom_iterator& other) const
    {
        return it_ == other.it_;
    }

    bool operator!=(const custom_iterator& other) const
    {
        return !(*this == other);
    }

private:

    something_that_exposes_the_type exposer_;
};