c++ - Preferred way to write custom iterators in C++17 -

this question has answer here:

• specializing iterator_traits 4 answers
• preparation std::iterator being deprecated 2 answers

beginning c++17 inheriting std::iterator<...> deprecated. instead 1 should specialize std::iterator_traits<...> own iterator type.

i used write iterator class nested types in container classes belong to.

trying partial specialize std::iterator_traits<c<t>> leads non-deducible context value type t container c.

the question: should (as of c++17) define iterator classes outside container classes?