string容器简单实现FDkLCL的博客-

string字符串在代码编辑中常常出现，本文主要介绍string内部常用函数的实现过程，关键点包含运算符的重载，左值拷贝和右值拷贝，左值运算符重载和右值运算符重载及迭代器的实现过程。相关函数未完全给出，以后会不断更新，敬请期待

 #include<iostream> #include<cstring> using namespace std;  class String { public:  String(const char* p = nullptr)  {   if (p != nullptr)   {    _pstr = new char[strlen(p) + 1];    strcpy(_pstr, p);   }   else   {    _pstr = new char[1];    *_pstr = '';   }  }  ~String()  {   delete[]_pstr;   _pstr = nullptr;  }  //带左值引用的拷贝构造  String(const String& str)  {   _pstr = new char[strlen(str._pstr) + 1];   strcpy(_pstr, str._pstr);  }  //带左值引用的赋值运算符重载  String& operator=(const String& str)  {   if (this == &str)    return *this;   delete[]_pstr;    _pstr = new char[strlen(str._pstr) + 1];   strcpy(_pstr, str._pstr);   return *this;  }  //带右值引用的拷贝构造  String(String&& str)  {   _pstr = str._pstr;   str._pstr = nullptr;  }  //带右值引用的赋值运算符重载  String& operator=(String&& str)  {   if (this == &str)    return *this;   delete[]_pstr;    _pstr = str._pstr;   str._pstr = nullptr;   return *this;  }  int length() { return strlen(_pstr); }  const char* c_str() { return _pstr; }  bool operator==(const String& str) { return strcmp(_pstr, str._pstr) == 0; }  bool operator!=(const String& str) { return strcmp(_pstr, str._pstr) != 0; }  char& operator[](int val) { return _pstr[val]; }  bool operator>(const String& str) { return strcmp(_pstr, str._pstr) > 0; }  bool operator<(const String& str) { return strcmp(_pstr, str._pstr) < 0; }    friend String operator+(String& str, String& lhs);  friend ostream& operator<<(ostream& out, const String& str); private:  char* _pstr;  class Iterator  {  public:   Iterator(char* p = nullptr)    :_p(p) {}   bool operator!=(const Iterator& it){return _p != it._p;}   void operator++(){++_p;}   char& operator*() { return *_p; }  private:   char* _p;  }; public:  Iterator begin(){return Iterator(_pstr);}  Iterator end(){return Iterator(_pstr + length());}  Iterator rbegin() { return Iterator(_pstr + length()); }  Iterator rend() { return Iterator(_pstr); } }; ostream& operator<<(ostream& out, const String& str) {  out << str._pstr;  return out; } String operator+(String& str, String& lhs) {  /*   这里返回的是值,不是指针或者是引用,原因在于   局部对象出作用域后会析构,无法找到局部对象的地址  */  String tmp;  tmp._pstr = new char[str.length() + lhs.length() + 1];  strcpy(tmp._pstr, str._pstr);  strcat(tmp._pstr, lhs._pstr);  return tmp; }  int main() {  String str("abc");  String str2("def");  String str3 = str + str2;  cout << str3 << endl;  string str4;  auto it = str3.begin();  /*   调用Iterator构造函数,begin返回的_pstr初始化_p  */  for (; it != str3.end(); ++it)  {   cout << *it << " ";  }  cout << endl;  cout << (str == str2) << endl;  return 0; }