C++（4）

1.myString类

头文件

#ifndef MYSTRING_H
#define MYSTRING_H

#include <iostream>
#include <cstring>

using namespace std;

class myString
{
private:
    char *str;//C风格字符串
    int size=0;
public:
    //无参构造
    myString();
    //有参构造
    //string s("hello world")
    myString(const char *s);
    //有参构造
    //string s(5,'A');
    myString(int n, const char s);
    //析构函数
    ~ myString();
    //拷贝构造函数
    myString(const myString &other);
    //拷贝赋值函数
    myString &operator=(const myString &other);
    //判空函数
    //返回1表示空，返回0表示非空
    bool empty();
    //size函数
    int str_size();
    //c_str函数
    const char* c_str() const;
    //at函数
    char &at(int index);
    //二倍扩容
    void expand();
    //+=运算符重载
    myString & operator+=(const myString &R);
    //取地址运算符重载
    const myString * operator&() const;
};

#endif // MYSTRING_H

源文件

#include "mystring.h"

//函数定义
//无参构造
myString::myString():size(10)
{
    str = new char[size];
    memset(str,'\0',10);
    cout<<"无参构造"<<endl;
}
//有参构造
//string s("hello world")
myString::myString(const char *s):size(strlen(s)+1)
{
    str = new char[size];
    strcpy(str,s);
    cout<<"有参构造"<<endl;
}
//有参构造
//string s(5,'A');
myString::myString(int n, const char s):size(n+1)
{
    str = new char[size];
    memset(str,s,n);
    str[n] = '\0';
    cout<<"有参构造"<<endl;
}
//析构函数
myString::~ myString()
{
    delete []str;
    cout<<"析构成功"<<endl;
}
//拷贝构造函数
myString::myString(const myString &other):size(other.size)
{
    str = new char[size];
    memcpy(str,other.str,size);
    cout<<"拷贝构造完成"<<endl;
}
//拷贝赋值函数
myString & myString::operator=(const myString &other)
{
    if(&other!=this)
    {
        delete []str;
        size = other.size;
        str = new char[size];
        strcpy(str,other.str);
        cout<<"拷贝赋值完成"<<endl;
    }
    return *this;
}
//判空函数
//返回1表示空，返回0表示非空
bool myString::empty()
{
    if(size==0||str[0]=='\0')
    {
        cout<<"该字符串为空"<<endl;
        return 1;
    }
    cout<<"该字符串非空"<<endl;
    return 0;
}
//size函数
int myString::str_size()
{
    cout<<"该字符串长度为"<<size<<endl;
    return size;
}
//c_str函数
const char* myString::c_str() const
{
    cout<<"该字符串为"<<str<<endl;
    return str;
}
//at函数
char &myString::at(int index)
{
    if(empty()||index<0||index>=size)
    {
        cout<<"查找失败"<<endl;
    }
    cout<<"该字符串下标为"<<index<<"的字符为"<<str[index]<<endl;
    return str[index];
}
//二倍扩容
void myString::expand()
{
    if(empty())
    {
        cout<<"二倍扩容失败"<<endl;
        return ;
    }
    char *nstr = new char[2*size];
    memcpy(nstr,str,size);
    delete []str;
    str = nstr;
    size*=2;
    cout<<"二倍扩容成功"<<endl;
}
//+=运算符重载
myString & myString::operator+=(const myString &R)
{
    int n_size = size+R.size-1;
    char *n_str = new char[n_size];
    strcpy(n_str,str);
    strcat(n_str,R.str);
    delete []str;
    str = n_str;
    size = n_size;
    return *this;
}
//取地址运算符重载
const myString * myString::operator&() const
{
    cout<<"取地址运算符重载完成"<<endl;
    return this;
}

主程序

#include "mystring.h"

int main()
{
    myString str1;
    myString str2("Hello world!");
    myString str3(10,'Z');
    myString str4(str2);
    myString str5("You are a genius.");
    str4.c_str();
    str4=str3;
    str4.c_str();
    str4.empty();
    str4.str_size();
    str3.c_str();
    str2.at(6);
    str2.expand();
    str2.str_size();
    str4+=str5;
    str4.c_str();
    str4.str_size();
    return 0;
}

2.思维导图

原文地址：https://blog.csdn.net/Af_22/article/details/145087552

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