自己实现string,加入迭代器功能

迭代器的功能:
提供一种统一的方式,来透明的遍历容器
理解 begin()方法,end()方法, ++ , * 的用处
其中 C++11 中提供的foreach的方式,其底层还是通过迭代器来进行遍历的.

#include using namespace std;class MyString2 {public://构造函数MyString2(const char * pSource = nullptr) {if (pSource != nullptr) {pString = new char[strlen(pSource) + 1];strcpy(pString, pSource);}else {pString = new char[1];pString[0] = '\0';}cout << "MyString构造函数,对象地址=" << this << endl;}//拷贝构造MyString2(const MyString2 & _rValue) {pString = new char[strlen(_rValue.pString) + 1];strcpy(pString, _rValue.pString);cout << "MyString拷贝构造函数" <pString;this->pString = nullptr;char * _tpString = new char[strlen(_rValue.pString) + 1];strcpy(_tpString, _rValue.pString);cout << "MyString赋值函数" <pString);if (indexlen) { return pString[index]; }else { return pString[index]; }}//不可编辑const char operator[](int index) const {int len = strlen(this->pString);if (indexlen) { return pString[index]; }else { return pString[index]; }}bool operator>(const MyString2 & _rValue) const {return strcmp(this->pString, _rValue.pString)>0;}bool operatorpString, _rValue.pString)pString, _rValue.pString) == 0;}int length() const {return strlen(this->pString);}~MyString2() {if (this->pString != nullptr) {delete[] this->pString;this->pString = nullptr;cout << "MyString析构函数" << this <pString; }//给Mystring 设计迭代器class Iterator {public:Iterator(char * _p=nullptr):p(_p) {this->p = _p;}    char & operator*() {return *p;}//前置++void operator++() {p++;}//bool operator!=(const Iterator & _val) {return p!=_val.p;}private:char * p;};// begin() 返回的 用MyString的首元素地址，通过Iterator封装一下Iterator begin() const {return  Iterator(this->pString);}// end() 返回的是 用 MyString 的最尾元素的下一个地址 再用Iterator封装一下    Iterator end() const {return  Iterator(this->pString+this->length());}private:char * pString;friend MyString2 operator+  (const MyString2 & s1, const MyString2 &s2);friend ostream & operator<<(ostream & out, const MyString2 &s);};MyString2 operator+(const MyString2 & s1, const MyString2 &s2) {/*方式1 这段代码有 内存泄漏问题  tp 没有释放掉int newLength = strlen(s1.pString) + strlen(s2.pString) + 1;char *tp = new char[newLength + 1];//重新申请空间strcpy(tp, s1.pString);strcat(tp, s2.pString);MyString s(tp);cout << "operator+ = " << &s << endl;return s;*//*方式2 对比方式1 效果更高*/MyString2 s;int newLength = strlen(s1.pString) + strlen(s2.pString) + 1;s.pString = new char[newLength + 1];//重新申请空间strcpy(s.pString, s1.pString);strcat(s.pString, s2.pString);cout << "operator+ = " << &s << endl;return s;}ostream & operator<<(ostream & out, const MyString2 &s) {cout << s.pString << endl;return out;}void test2() {MyString2 s1("12345");MyString2 s2("6789ABC");cout << s1 << endl;cout << s2 << endl;MyString2 s3 = s1 + s2;cout << s3 << endl;cout << "s3 = " << &s3 << endl;for (int i = 0; i < s3.length(); i++) {cout << s3[i] << endl;}cout << "--------------------" << endl;s3[0] = 'W';for (int i = 0; i < s3.length(); i++) {cout << s3[i] << endl;}const MyString2 s4("hello");for (int i = 0; i < s4.length(); i++) {cout << s4[i] << endl;}cout << "------iterator Begin------" << endl;MyString2::Iterator it_begin = s4.begin();MyString2::Iterator it_end   = s4.end();for (  ;it_begin!=it_end; ++it_begin) {cout << *it_begin <<" ";}cout << endl;cout << "------iterator End------" << endl;}int main() {test2();system("pause");return 0;}