Returning an 'any kind of input iterator' instead of a vector::iterator or a list::iterator [duplicate]

Question

This question already has answers here: Generic iterator (3 answers) Closed 7 years ago. Suppose I want to implement in C++ a data-structure to store oriented graphs. Arcs will be stored in Nodes thanks to STL containers. I'd like users to be able to iterate over the arcs of a node, in an STL-like way. The issue I have is that I don't want to expose in the Node class (that will actually be an abstract base class) which STL container I will actually use in the concrete class. I therefore don't want to have my methods return std::list::iterator or std::vector::iterator... I tried this: class Arc; typedef std::iterator ArcIterator; // Wrong! class Node { public: ArcIterator incomingArcsBegin() const { return _incomingArcs.begin(); } private: std::vector _incomingArcs; }; But this is not correct because a vector::const_iterator can't be used to create an ArcIterator. So what can be this ArcIterator? I found this paper about Custom Iterators for the STL but it did not help. I must be a bit heavy today... ;) JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

Try this: class Arc; class Node { private: std::vector incoming_; public: typedef std::vector::iterator iterator; iterator incoming_arcs_begin() { return incoming_.begin(); } }; And use Node::iterator in the rest of the code. When/if you change the container, you have to change the typedef in a single place. (You could take this one step further with additional typedef for the storage, in this case vector.) As for the const issue, either define vector's const_iterator to be your iterator, or define double iterator types (const and non-const version) as vector does.