implementing an iterator

iterator_Example.cpp

//============================================================================
// Name        : class_02.cpp
// Author      : Kumail Ahmed
// Version     :
// Copyright   : Your copyright notice
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
#include <iterator>
#include <numeric>
using namespace std;

template<typename T>
class RefIter {
public:
    // Iterator traits, previously from std::iterator.
    using value_type = T;
    using difference_type = std::ptrdiff_t;
    using pointer = T*;
    using reference = T&;
    using iterator_category = std::forward_iterator_tag;

  RefIter() = default;

  RefIter(int* input_ref, int _size) : size(_size) {
	  it_refs = new T(_size);
	  for(int i = 0; i < _size; i++) {
		  *(it_refs + i ) = *(input_ref +i);
	  }
  }
  reference operator*() const {
	  return it_refs[current];
  }
  pointer operator->() const {
	  return &it_refs[current];
  }

  // Move position forward 1 place
  RefIter& operator++() {
	  ++current;
	  return *this;
  }

  RefIter operator++(int) {
	  RefIter tmp = *this;
	  ++current;
	  return tmp;
  }

  // Comparison operators
  bool operator== (const RefIter& rhs) {
	  return current == rhs.current;
  }

  bool operator!= (const RefIter& rhs) {
	  return (current < size);
  }

private:
  T* it_refs;
  int size;
  int current {0};


};

class Book {
private:
	int bookID;
	int* refs;
	int size;
public:

	Book(int _bookID, int* _refs, int _size) : bookID(_bookID), size(_size) {
		refs = new int(_size);
		refs = _refs;
	}

	Book() {
		bookID=-1;
		size = 0;
		refs = nullptr;
	}

	Book(const Book& b) {
		bookID = b.bookID;
		size = b.size;
		refs = new int(b.size);
		for (int i = 0; i < b.size; i++)
			*(refs + i) = *(b.refs + i);
	}

	void printRefs() const {
		cout << "BookID: " << bookID << endl;
		for(int i = 0 ; i < size; i++) {
			cout << "refs values at " << i << " is " << *(refs+i) << endl;
		}

	}

	void changeRefs(int *_refs, int _size) {
		delete [] refs;
		refs = new int(_size);
		for (int i = 0; i < _size; i++)
			*(refs+ i) = *(_refs + i);
		size = _size;
	}

	friend void swap(Book& lhs, Book& rhs) {
		using std::swap;
		swap(lhs.bookID, rhs.bookID);
		swap(lhs.size, rhs.size);
		swap(lhs.refs, rhs.refs);
	}

	Book& operator=(Book b) {
		swap(*this, b);
		return *this;
	}


	~Book() {
		delete[] refs;
	}

	using iterator = RefIter<int>;

	iterator begin() const { return iterator(refs, size);}
	iterator end() const { return   iterator(nullptr, 0);}

};






int main() {

	int refIDs[] = {1,2,3,4,5};
//	int refIDs2[] = {10,20,30,40,50,60,70,80,90};

	Book b1(0, refIDs, 5);

//	Book b3;
//	b3 = b1;
//
//	b3.printRefs();
//	cout << "=============\n";
//	b1.changeRefs(refIDs2, 9);
//	b3 = b1;
//	b3.printRefs();

	Book::iterator v0 = ++b1.begin();
	Book::iterator v1 = v0;

	if(v0 == v1)
		cout << "equal" << endl;

	cout << "sum: "
		 << accumulate(b1.begin(), b1.end(),0) << endl;

	for(auto& BI : b1)
		cout << "value is: " << BI << endl;

	return 0;
}