MyString类的实现

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string类在c++中使得程序员对于字符串的操作更加方便，今天就来编写自己的MyString类。

先来看mystring.h的定义：

#ifndef _MYSTRING_H_#define _MYSTRING_H_#include<iostream>using namespace std;class MyString{public:    MyString();    MyString(const char* str);    MyString(const size_t len,const char ch);    MyString(const MyString& t);    ~MyString();public:    //属性    size_t length();    bool empty();    const char* c_str();    //返回C风格字符串指针    //读写操作    friend ostream& operator<< (ostream& out,const MyString& str);    friend istream& operator>> (istream& in, MyString& str);    //'+'操作    friend MyString operator+ (const MyString& str1,const MyString& str2);    //比较操作    friend bool operator== (const MyString& str1,const MyString& str2);    friend bool operator!= (const MyString& str1,const MyString& str2);    friend bool operator< (const MyString& str1,const MyString& str2);    friend bool operator<= (const MyString& str1,const MyString& str2);    friend bool operator> (const MyString& str1,const MyString& str2);    friend bool operator>= (const MyString& str1,const MyString& str2);    //下标操作    char& operator[] (const size_t);    const char& operator[] (const size_t)const;    //赋值操作    MyString& operator= (const MyString& str);    //'+='操作    MyString& operator+= (const MyString& str);    //子串操作    MyString substr(size_t,size_t);    //添加操作    MyString& append(const MyString& str);    //插入操作    MyString& insert(size_t,const MyString&);    //替换操作    MyString& assign(const MyString&,size_t,size_t);    //删除操作    MyString& erase(size_t,size_t);private:    char *base;    size_t strlength;};#endif

接下来来看具体的实现：

#include<iostream>#include<string>#include<string.h>#include<assert.h>#include"mystring.h"MyString::MyString(){    base = NULL;    strlength = 0;}MyString::MyString(const char* str){    if(str == NULL){        return ;    }    strlength = strlen(str);    base = new char[strlength + 1];    strcpy(base,str);    }MyString::MyString(size_t len,const char ch){    strlength = len;    base = new char[strlength + 1];    base[strlength + 1] = '\0';    for(int i = 0;i< strlength;++i){        base[i] = ch;    }}MyString::MyString(const MyString& t){    this->strlength = t.strlength;    base = new char[strlength + 1];    strcpy(base,t.base);}MyString::~MyString(){    delete []base;}size_t MyString::length(){    return strlength;}bool MyString::empty(){    return strlength == 0 ? true : false;}const char* MyString:: c_str()    //返回C风格字符串指针{    return base;}//下标操作char& MyString::operator[] (const size_t index){    assert(index >=0 && index <= strlength);    return base[index];}const char& MyString::operator[] (const size_t index)const{    assert(index >=0 && index <= strlength);    return base[index];}//赋值操作MyString& MyString::operator= (const MyString& str){    if(this != &str){        delete []base;        base = new char[str.strlength + 1];        strlength = str.strlength ;        strcpy(base,str.base);           }    return *this;}//'+='操作MyString& MyString::operator+= (const MyString& str){    if(this != &str){        strlength += str.strlength;        char *p_str;        p_str = new char[strlength + 1];        strcpy(p_str,base);        delete []base;        strcat(p_str,str.base);        base = p_str;        return *this;    }    MyString copy(str);    return *this += copy;}//子串操作//返回一个MyString 类型的字符串，它包含源字符串中从下标pos开始的n个字符MyString MyString::substr(size_t pos,size_t n){    assert(pos + n <= strlength);    MyString ret;    ret.strlength = n;    ret.base = new char[ret.strlength + 1];    for(size_t i = 0;i < n;++i){        ret[i] = base[pos + i];    }    ret[ret.strlength] = '\0';    return ret;}//添加操作//将一个字符串的副本添加源字符串的末尾，同"+="操作符类似MyString& MyString::append(const MyString& str){    *this += str;    return *this;}//插入操作//在下标pos的元素之前插入MyString对象str的副本MyString& MyString::insert(size_t pos,const MyString& str){    assert(pos < strlength);    int len = str.strlength;    int len1 = strlength ;    char *p_str;    int i;    strlength += str.strlength;    p_str  = new char[strlength + 1];    for(i = 0; i < pos;++i){        p_str[i] = base[i];    }    for(int j = 0 ; j < str.strlength;++j){        p_str[i++] = str[j];    }    for(int k = pos ; k <= len1;++k){        p_str[i++] = base[k];    }    p_str[strlength] = '\0';    delete []base;    base = p_str;    return *this;}//替换操作//用s2中下标pos开始的len个字符副本替换源字符串MyString& MyString::assign(const MyString& s2,size_t pos,size_t len){    if(strlength < len){        char* p_str = new char[len + 1];        strlength = len;        delete []base;        base = p_str;    }    int i;    for(i = 0;i < len;++i){        base[i] = s2[i];    }    base[strlength] = '\0';    return *this;}//删除操作//删除从下标pos开始的len的字符MyString& MyString::erase(size_t pos,size_t len){    assert(pos + len <= strlength);    for(int i = pos ,j = pos + len ; i < pos + len && j <= strlength ; ++i,++j){        base[i] = base[j];    }    strlength -= len;    base[strlength] = '\0';    return *this;}//读写操作ostream& operator<<(ostream& out,const MyString& t){    if(t.base != NULL){        cout << t.base;    }    return out;}istream& operator>> (istream& in, MyString& str){    char tmp[100];    if(in >> tmp){        delete []str.base;        str.strlength = strlen(tmp);        str.base = new char[str.strlength + 1];        strcpy(str.base,tmp);    }    return in;}//'+'操作MyString operator+ (const MyString& str1,const MyString& str2){    MyString ret;    ret.strlength = str1.strlength + str2.strlength ;    ret.base = new char[ret.strlength + 1];    strcpy(ret.base,str1.base);    strcat(ret.base,str2.base);    return ret;}//比较操作bool operator== (const MyString& str1,const MyString& str2){    return strcmp(str1.base , str2.base) == 0;}bool operator!= (const MyString& str1,const MyString& str2){    return strcmp(str1.base , str2.base) != 0;}bool operator< (const MyString& str1,const MyString& str2){    return strcmp(str1.base , str2.base) < 0;}bool operator<= (const MyString& str1,const MyString& str2){    return strcmp(str1.base , str2.base) <= 0;}bool operator> (const MyString& str1,const MyString& str2){    return strcmp(str1.base , str2.base) > 0;}bool operator>= (const MyString& str1,const MyString& str2){    return strcmp(str1.base , str2.base) >= 0;}

测试程序：

#include<iostream>#include<string>#include"mystring.h"#include<string.h>using namespace std;int main(int argc,char**argv){    MyString s;    MyString s1("hello");    MyString s2(10,'h');    MyString s3 = s1;    MyString s4("world");    MyString s5(10,'e');    MyString s6("family");    const char *str = s.c_str();    const char *str1 = s1.c_str();    const char *str2 = s2.c_str();    const char *str3 = s3.c_str();    #if 1    cout << s <<endl;    cout << "s length : " << s.length() << endl;    if(s.empty()){        cout << "s is empty!"<<endl;    }else{        cout << "s is not empty!!" << endl;    }    cout << s1 <<endl;    cout << "s1 length : " << s1.length() << endl;    if(s1.empty()){        cout << "s1 is empty!"<<endl;    }else{        cout << "s1 is not empty!!" << endl;    }    cout << s2 <<endl;    cout << "s2 length : " << s2.length() << endl;    if(s2.empty()){        cout << "s2 is empty!"<<endl;    }else{        cout << "s2 is not empty!!" << endl;    }    cout << s3 <<endl;    cout << "s3 length : " << s3.length() << endl;    if(s3.empty()){        cout << "s3 is empty!"<<endl;    }else{        cout << "s3 is not empty!!" << endl;    }   //cout << "s c_str(): " << str << endl;   cout << "s1 c_str(): " << str1 << endl;   cout << "s2 c_str(): " << str2 << endl;   cout << "s3 c_str(): " << str3 << endl;    cout << "s1[] :" << endl;    for(int i = 0;i <= s1.length() ;++i){        cout << s1[i] << " ";    }    cout << endl;    cout << "s2[] :" << endl;    for(int i = 0;i <= s2.length() ;++i){        cout << s2[i] << " ";    }    cout << endl;    cout << "s3[] :" << endl;    for(int i = 0;i <= s3.length() ;++i){        cout << s3[i] << " ";    }    cout << endl;       s3 = s2;    cout << "s3 = s2 : " << endl;    cout << "s3 : "<< s3 << endl;        s1 += s4;    cout << "s1 += s4 : " << s1 << endl;    s1 += s1;    cout << "s1 += s1 : " << s1 << endl;    s2 += s1;    cout << "s2 += s1 : " << s2 << endl;    s2 += s2;    cout << "s2 += s2 : " << s2 << endl;    #endif    s = s1.substr(0,4);    cout << "s1.substr(): " << s << endl;        #if 1    s4 = s1.append(s4);    cout <<"s1: " << s1 <<endl;    cout <<"s4: " << s4 <<endl;            cout << "s4 : " << s4 << endl;    cout << "s5 : " << s5 << endl;    s4.insert(1,s5);    cout << "s4 (befor 1)insert s5 :    " << endl ;    cout << "s4 : " << s4 << endl;    cout << endl;    cout << "s5 : " << s5 << endl;    cout << "s6 : " << s6 << endl;    s6.insert(1,s5);    cout << "s6 (befor 1) insert s5 :    " << endl ;    cout << "s5 : " << s5 << endl;    cout << "s6 : " << s6 << endl;    cout << endl;    #endif    #if 1    cout << "s2 : " << s2 << endl;    cout << "s6 : " << s6 << endl;    s6.assign(s2,0,10);    cout << "s2 (0,10) assgin s6:    " << endl ;    cout << "s2 : " << s2 << endl;    cout << "s6 : " << s6 << endl;    cout << endl;        cout << "s2 : " << s2 << endl;    cout << "s6 : " << s6 << endl;    s6.assign(s2,0,20);    cout << "s2 (0,20) assgin s6:    " << endl ;    cout << "s2 : " << s2 << endl;    cout << "s6 : " << s6 << endl;    cout << "s5 :" << endl;    cout << s5 << endl;    cout << "s6 :" << endl;    cout << s6 << endl;    cout << "s6 : " <<endl;    cout << s6 << endl;    s6.erase(1,15);    cout << "s6 erase : " <<endl;    cout << s6 << endl;       cout << "s5 :" << endl;    cout << s5 << endl;    cout << "s6 :" << endl;    cout << s6 << endl;    s6 = s5 + s6;    cout << "s6  = s5 + s6 " << endl;    cout << s6 << endl;      cout << endl;     cout << "s5 :" << endl;    cout << s5 << endl;    cout << "s6 :" << endl;    cout << s6 << endl;    if(s5 > s6){        cout << "s5 > s6 " << endl;    }    if(s5 >= s6){        cout << "s5 >= s6 " << endl;    }    if(s5 == s6){        cout << "s5 == s6 " << endl;    }    if(s5 != s6){        cout << "s5 != s6 " << endl;    }    if(s5 < s6){        cout << "s5 < s6 " << endl;    }    if(s5 <= s6){        cout << "s5 <= s6 " << endl;    }    #endif    return 0;}

部分执行结果：

通过string类的编写更加深刻体会到c++的面向对象的特点，之后还会继续对继承和多态，甚至设计模式都会有比较深的理解的。。。

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