C++ String类编写

1. h文件

#ifndef _STR_H_
#define _STR_H_
#include 
using namespace std;

class String
{
public:
    String();                           //默认构造函数
    String(const char*s);         //普通构造函数
    String(const String& s);            //复制构造函数
    String& operator=(char* s);         //重载=,实现字符串赋值
    String& operator=(const String& s); //重载=,实现对象赋值
    ~String();                         //析构函数
    char& operator[](int i);            //重载[],实现数组运算
    const char& operator[](int i) const;    // 重载[],实现数组运算,对象为常量
	String&operator+(const String& s);
    String& operator+=(const String& s);    //重载+=,实现与对象相加
    String& operator+=(const char* s);      //重载+=,实现与字符串相加
    friend ostream& operator<<(ostream& out, String& s);    //重载<<
    friend istream& operator>>(istream& in, String& s);     //重载>>
    friend bool operator<(const String& left, const String& right);     //重载<
    friend bool operator>(const String& left, const String& right);     //重载>
    friend bool operator==(const String& left, const String& right);    //重载==
    friend bool operator!=(const String& left, const String& right);    //重载!=
    char* getData();
private:
    int size;       //data表示的字符串长度
    char* data;     //指向字符串数据
};
#endif

2. cpp文件

#include "str.h"
String::String(){
    data = new char[1];
    *data = '\0';
    size = 0;
}
String::String(const char* s){
    if (s == NULL) {
        data = new char[1];
        *data = '\0';
        size = 0;
    }else{
        size = strlen(s);
        data = new char[size + 1];
        strcpy(data,s);
    }
}
String::String(const String& s){
    size = s.size;
    data = new char[s.size+ 1];
    strcpy(data,  s.data);
}
String& String::operator=(char *s)
{
	
    if (data != NULL)
        delete[] data;
	if(s==NULL){
	     data = new char[1];
        *data = '\0';
        size = 0;
		return *this;
	}else{
        size = strlen(s);
        data = new char[size + 1];
        strcpy(data, s);
        return *this;
	}
}
String& String::operator=(const String& s)
{
    if (this == &s)
        return *this;
    if (data != NULL) 
        delete[] data;
    size = s.size;
    data = new char[size + 1];
    strcpy(data, s.data);
    return *this;
}

String::~String()
{
	cout<<"deconstruct"<data=new char[size+s.size+1];
	pstring->size=size+s.size;
	strcpy(pstring->data,data);
	strcat(pstring->data,s.data);
	return *pstring;
}

String& String::operator+=(const char* s)
{
    if (s == NULL)
    {
        return *this;
    }
    int len = size + strlen(s) + 1;
    char *temp = data;
    data = new char[len];
    strcpy(data, temp);
    strcat(data,s);
    delete[] temp;
    size = len - 1;
    return *this;
}
String& String::operator+=(const String& s)
{
   int len=size+s.size+1;
   char *temp=data;
   data=new char[len];
   strcpy(data,temp);
   delete[]temp;
   strcat(data,s.data);
   size = len - 1;
    return *this;
}
ostream& operator<<(ostream& out, String& s)
{
    for (int i = 0; i < s.size; i++)
        out << s[i] ;
    return out;
}

istream& operator>>(istream& in, String& s)
{
    char p[50];
    in.getline(p, 50);      //从输入流接受最多50个字符
    s = p;                  //调用赋值函数
    return in;
}

bool operator<(const String& left, const String& right) //重载<
{
    int i = 0;
    while (left[i] == right[i] && left[i] != 0 && right[i] != 0)
        i++;
    return left[i] - right[i] < 0 ? true : false;
}

bool operator>(const String& left, const String& right) //重载<
{
    int i = 0;
    while (left[i] == right[i] && left[i] != 0 && right[i] != 0)
        i++;
    return left[i] - right[i] > 0 ? true : false;
}

bool operator==(const String& left, const String& right)
{
    if (left.size != right.size)
        return false;
    for (int i = 0; i < left.size; i++)
    {
        if (left.data[i] != right.data[i])
            return false;
    }
    return true;
}

bool operator!=(const String& left, const String& right)
{
    if (left.size != right.size)
        return true;
    for (int i = 0; i < left.size; i++)
    {
        if (left.data[i] != right.data[i])
            return true;
    }
    return false;
}

3.main函数

#include "str.h"

int main()
{
    String str1;//默认构造函数
    String str2("asdf");//普通构造函数
    String str4("hello world");//普通构造函数
    String str3=str2;//复刻构造函数
    cout << "str1: " << str1 << endl;
    cout << "str2: " << str2 << endl;
    cout << "str3: " << str3 << endl;

	//str3 = NULL;//赋值函数特例
    //cout << "str3: " << str3 << endl;

    str3 = str4;//赋值函数
    cout << "str3: " << str3 << endl;
    
    cout << "str3[2]: " << str3[2] << endl;

    str3 += "111";
    cout << "str3: " << str3 << endl;
    str3 += str2;
    cout << "str3: " << str3 << endl;

    cout<<"input start"<> str1;
    cout << "str1: " << str1 << endl;

	str4=str4+str1;
    cout << "str4: " << str4 << endl;

    String t1 = "1234";
    String t2 = "1234";
    String t3 = "12345";
    String t4 = "12335";

    cout << "t1 == t2 ? " << (t1 == t2) << endl;
    cout << "t1 < t3 ? " << (t1 < t3) << endl;
    cout << "t1 > t4 ? " << (t1>t4) << endl;
    cout << "t1 != t4 ? " << (t1 != t4) << endl;
    return 0;
}

 

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