String类的C++实现

最新推荐文章于 2022-05-09 11:38:26 发布

原创最新推荐文章于 2022-05-09 11:38:26 发布 · 380 阅读

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CC 4.0 BY-SA版权

文章标签：

#string #c++ #constructor #null #delete #io

本文介绍了一个自定义String类的设计与实现，包括构造函数、赋值运算符、拼接运算符等关键成员函数。通过深入解析每个函数的作用及其实现方式，帮助读者理解字符串类的基本操作。

可能很多人在ms的时候都会碰到这个问题，我也碰到过。网上也有很多这样的资源，个人觉得有些实现还是存在着问题的。所以在我的博客中总结出来：

class String
{
public:

String(const char* str=NULL); //赋值构造兼默认构造函数(char)

String(const String &other);
String& operator=(const String &other);        //operator=
String& operator=(const char *ch);        //operator=
String& operator+(const String&other);   //operator+
bool operator==(const String&other);  //operator==
char& operator[](unsigned int);
size_t size(){return strlen(m_data)};
~String(){delete [] _string;};

private:
char *_string;
size_t _size;

friend ostream& operator<< (ostream&,String&);

}

//assign constructor & default constructor
String::String(const char *str)
{
int n;
if(str==NULL)
{
  _string = 0;
  _size = 0;
}
else
{
  _size = strlen(str);
  _string = new char[_size+1];
  strcpy(_string, str);
}

}

//copy constructor
String::String(const String &rhs)
{
_size = rhs._size;

if(rhs._string == NULL)
  _string = NULL;
else
{
  _string = new char[_size+1];
  strcpy(_string, rhs._string);
}
}

//= operator
String::String& operator=(const char *ch);
{

if(ch == NULL)
{
  _size = 0;
  _string = NULL;
}
else
{
  _size = strlen(ch);
  _string = new char[_size+1];
  strcpy(_string, ch);
}
return *this;
}

String::String &operator =(const String&other)
{
if(this != &other)
{
  delete []m_data;
  _size = other._size;
  if( other._string == NULL)
  {
   _string = NULL;
  }
  else
  {
   _string = new char[_size+1];
   strcpy(_string, other._string);
  }
}
return *this;
}

//operator []
String::char &operator[](unsigned int i)
{
assert(i>=0 && i<= _size)
return _string[i];
}

istream &operator>>(istream &io, String &s)
{
const int limit_string_size = 4096;
char inBuf[limit_string_size];

io >>setw(limit_string_size)>> intBuf;
s = intBuf;

return io;
}

ostream &operator<<(ostream &io, String &s)
{
return os<<s.c_str();
}

String::String &operator +(const String &rhs)
{
String newString;

if(rhs._string == NULL)
{
  newString = *this;
}
else if(_string == NULL)
{
  newString = rhs;
}
else
{
  newString._size = strlen(_string)+strlen(other._string);
  newString._string = new char[newString._size+1];
  strcpy(newString._string, _string);
  strcat(newString._string, rhs._string);
}
return newString;
}