c++ 基于文件的增删改查-蒲公英云

c++ 基于文件的增删改查

wuzhixiang

#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <iomanip>
#include <windows.h>
#define WIDTH 20
#define space setw(WIDTH)
#define NEWLINE "\r\n"
using namespace std;
void write(const char *filename)
{
    ofstream out;
    out.open(filename,ios::app);
    if(!out.is_open())
    {
        cout<<"open error"<<endl;
        return ;
    }
    else
    {
        int id,age;
        string name;
        cout<<"请输入id、姓名、年龄："<<endl;
        cin>>id>>name>>age;
        out.fill(' ');
        out.setf(ios::left);
        out<<space<<id<<space<<name<<space<<age<<NEWLINE;
        out.close();
        cout<<"添加成功！！"<<endl;
    }
}
void read(const char *filename)
{
    ifstream in;
    in.open(filename,ios::in);
    if(!in.is_open())
    {
        cout<<"file open error"<<endl;
        return ;
    }
    else
    {
        stringstream ss;
        char line[100];
        cout.setf(ios::left);
        cout.fill(' ');
        cout<<space<<"id"<<space<<"name"<<space<<"age"<<endl;
        while(in.peek()!=EOF)
        {
            in.getline(line,100);
            ss<<line;
            int id,age;
            string name;
            ss>>id>>name>>age;
            cout<<space<<id<<space<<name<<space<<age<<endl;
            ss.str("");
            ss.clear();
        }
        in.close();
    }
}
void del(const char *filename)
{
    int id;
    cout<<"请输入您要删除学生的编号"<<endl;
    cin>>id;
    ifstream in;
    in.open(filename,ios::in);
    if(!in.is_open())
    {
        cout<<"file open error"<<endl;
        return ;
    }
    else
    {
        string temp;
        stringstream ss;
        int curId;;
        while(in.peek()!=EOF)
        {
            string line;
            getline(in,line);
            ss<<line;
            ss>>curId;
            if(curId!=id)
            {
                temp += line + NEWLINE;
            }
            ss.str("");
            ss.clear();
        }
        in.close();
        ofstream out;
        out.open("G:\\students.txt",ios::out);
        if(!out.is_open())
        {
            cout<<"file open error"<<endl;
            return ;
        }
        else
        {
            out<<temp;
            out.close();
            cout<<"删除成功！！"<<endl;
        }
    }
}
int search_pos(const char *filename,int id)
{
    ifstream in;
    in.open(filename,ios::in|ios::binary);
    if(!in.is_open())
    {
        cout<<"file open error"<<endl;
        return -1;
    }
    else
    {
        stringstream ss;
        while(in.peek()!=EOF)
        {
            int start = in.tellg();
            string line;
            getline(in,line);
            ss<<line;
            int curID;
            ss>>curID;
            if(curID == id)
            {
                in.close();
                return start;
            }
            ss.str("");
        }
        cout<<"对不起您查找的同学信息不存在!"<<endl;
        in.close();
    }
    return -1;
}
void search(const char *filename)
{
    cout<<"请输入您要查找的学生id："<<endl;
    int id;
    cin>>id;
    int pos = search_pos(filename,id);
    string line;
    fstream in;
    in.open(filename,ios::in|ios::binary);
    in.seekg(pos,ios::beg);
    getline(in,line);
    cout.setf(ios::left);
    cout<<space<<"id"<<space<<"name"<<space<<"age"<<endl;
    cout<<line<<endl;
}
void edit(const char *filename)
{
    int id,age;
    string name;
    cout<<"请输入您要修改的学生id"<<endl;
    cin>>id;
    cout<<"请输入该学生新的姓名、年龄"<<endl;
    cin>>name>>age;
    stringstream infoTemp;
    infoTemp.fill(' ');
    infoTemp.setf(ios::left);
    infoTemp<<space<<id<<space<<name<<space<<age;
    string newInfo;
    getline(infoTemp,newInfo);
    fstream file;
    file.open(filename,ios::in|ios::out|ios::binary);
    if(!file.is_open())
    {
        cout<<"file open error"<<endl;
        return ;
    }
    else
    {
        int pos = search_pos(filename,id);
        file.seekg(pos,ios::beg);
        file<<newInfo;
        cout<<"修改后信息为："<<endl;
        cout<<newInfo<<endl;
        file.close();
    }
}
int main()
{
    const char *filename = "G:\\students.txt";
    while(true)
    {
        cout<<"--------------------------"<<endl;
        cout<<"0、查看全部信息"<<endl;
        cout<<"1、新增学生信息"<<endl;
        cout<<"2、删除学生信息"<<endl;
        cout<<"3、修改学生信息"<<endl;
        cout<<"4、查找学生信息"<<endl;
        int cmd;
        cin>>cmd;
        system("cls");
        switch(cmd)
        {
            case 0:read(filename);break;
            case 1:write(filename);break;
            case 2:del(filename);break;
            case 3:edit(filename);break;
            case 4:search(filename);break;
        }
    }
    return 0;
}