《Essential C++》系列笔记之第四章(基于对象的编程风格)之第六节(打造一个Iterator Class)

代码实践

• Triangular.h

  #pragma once
  #include 
  #include 
  #include "Triangular_iterator.h"
  using namespace std;
  
  class Triangular_iterator;
  class Triangular
  {
  	friend class Triangular_iterator; //把Triangular_iterator声明为友元类,记得包含类的头文件
  public:
  	typedef Triangular_iterator iteraotr;
  
  	/*Triangular_iterator begin() const
  	{
  		return Triangular_iterator(_beg_pos);
  	}*/
  	//Triangular_iterator a;
  
  	Triangular(const Triangular&);
  	Triangular(int, int);
  
  	int lenth() const { return _length; }
  	int beg_pos() const { return _beg_pos; }
  	int elem(int) const;
  
  	void next_reset() const{ _next = _beg_pos - 1; }
  	bool next(int& val) const;
  
  	int sum(const Triangular&);
  
  private:
  	string _name;
  	int _length; //元素个数
  	int _beg_pos; //起始位置
  	mutable int _next;   //下一个迭代目标
  	static vector<int> _elems;
  };
  
  

• Triangular.cpp

  #include "Triangular.h"
  
  vector<int> Triangular::_elems; //static data member只有唯一实体,必须在cpp中提供清楚的定义
  
  Triangular::Triangular(const Triangular& rhs)
  	:_length(rhs._length), _beg_pos(rhs._beg_pos), _next(rhs._next)
  {}
  
  Triangular::Triangular(int len, int bp)
  	: _name("Triangular")
  {
  	this->_length = (len > 0 ? len : 1);
  	this->_beg_pos = (bp > 0 ? len : 1);
  	this->_next = this->_beg_pos - 1;
  }
  
  int Triangular::elem(int pos) const
  {
  	return _elems[pos - 1];
  }
  
  bool Triangular::next(int& val) const
  {
  	if ( _next < _beg_pos + _length - 1 )
  	{
  		val = _elems[_next++];
  		return true;
  	}
  	return false;
  }
  
  int Triangular::sum(const Triangular& trian)
  {
  	return 0; //只是测试
  }
  

• Triangular_iterator.h

  #pragma once
  #include "Triangular.h"
  class Triangular_iterator
  {
  	friend class Triangular;
  public:
  	Triangular_iterator(int index) : _index(index - 1) {}
  	bool operator==(const Triangular_iterator&)const;
  	bool operator!=(const Triangular_iterator&)const;
  	int operator*()const;
  	Triangular_iterator& operator++();
  	Triangular_iterator& operator++(int);
  private:
  	void check_integrity() const;
  	int _index;
  };
  
  

• Triangular_iterator.cpp

  #include "Triangular_iterator.h"
  
  //vector Triangular::_elems; //static data member只有唯一实体,必须在cpp中提供清楚的定义
  bool Triangular_iterator::operator==(const Triangular_iterator&rhs) const
  {
  	return _index == rhs._index;
  }
  
  bool Triangular_iterator::operator!=(const Triangular_iterator&rhs) const
  {
  	return  !(*this == rhs); 
  }
  
  int Triangular_iterator::operator*() const
  {
  	//check_integrity();
  	return Triangular::_elems[_index];
  }
  
  

今天是20200324 我一定会回来的!