文件流
C++标准库头文件—#include<fstream>，包含：ofstream,ifstream,fstream
open打开文件，close关闭文件
主要注意的是同个文件可同时被打开多次，但是不可以在同个作用域内同时进行IO处理，所以在函数内打开文件并对它处理的时候，记得在最后关闭文件。
ios::in 从文件读取信息
ios::out 向文件写入信息
ios::app 所有写入都追加到文件末尾
ios::trunc 清空文件后打开文件
读取文件内容一般使用getchar读取一个字母和getline读取一行字符串
eof()函数的判断文件指针是否在最后，故配合eof()可以进行对文件行数的统计等
fstream file(filename,ios::out);
string s;
int row=0;//行数
while(!file.eof())
{
getline(file,line);
row++;
}
切记勿直接对文件处理，而是把文件的数据先存储到计算机中，再对计算机内的容器进行操作。
例如：在学生信息管理系统中需要定义个student的类，我们就可以定义一个vector<student>的数组存储它；while循环中每次getline一个字符串string后，对字符串进行遍历，巧妙对空格进行判断，让对应的子串赋值给对应的数据,记的留类变量的接口。
friend void read(string filename, vector<student>& a)//文本读出
{
fstream file(filename, ios::in);
string line;
getline(file, line);//先读取文件最顶行的说明保证它不影响数据存储
while (!file.eof())
{
student* temp = new student;
string str = "", s[10];
int num = 0;
getline(file, line, '\n');
for (int i = 0; i < line.size(); i++)
{
if ((line[i] == ' ' || line[i] == '\t') && str != "") {
s[num] = str;
num++;
str = "";
}
else if (line[i] != ' ' && line[i] != '\t')
str += line[i];
}
s[num] = str;
if (s[0] != "" && s[1] != "" && s[2] != "" && s[3] != "" && s[4] != "" && s[5] != "" && s[6] != "")
{
temp->SetInformation(s[0], s[1], s[2], s[3], s[4], s[5], s[6]);//学号 姓名 性别 年龄 班级 专业 系别
a.push_back(*temp);
}
delete temp;
}
file.close();
}
//把修改好的学生信息内容，从vector容器中入读文本，向文本写入
friend void wirte(string filename, vector<student>a)
{
fstream file(filename, ios::out | ios_base::trunc);
file << std::right << "学号" << setw(10) << "姓名" << setw(10) << "性别" << setw(10) << "年龄" << setw(10) << "班级"
<< setw(10) << "专业" << setw(10) << "系别" << endl;
for (int i = 0; i < a.size(); i++)
{
file << a[i].GetId() << setw(10) << a[i].GetName() << setw(10) << a[i].GetSex() << setw(10)
<< a[i].GetAge() << setw(10) << a[i].GetClubm() << setw(10) << a[i].GetMajor()
<< setw(10) << a[i].GetDepartment() << endl;
}
file.close();
}
在对学生信息进行操作管理，
添加，new一个student，最后push_back；
friend void input(vector<student>& a)
{
cout << "请输入学生的学号、姓名、性别(male or female)、年龄、班级、专业、系别(请用空格隔开每个输入)" << endl;
student* temp = new student;
string mId, mName, mSex, mAge, mClubm, mMajor, mDepartment;
cin >> mId >> mName >> mSex >> mAge >> mClubm >> mMajor >> mDepartment;
temp->SetID(mId); temp->SetName(mName); temp->SetSex(mSex);
temp->SetAge(mAge); temp->SetMajor(mMajor); temp->SetDepartment(mDepartment);
a.push_back(*temp);
delete temp;
cout <<setw(12)<< "添加成功" << endl;
}
删除，先找到要删除的学生，从这个删除的学生开始，让前一名学生等于后一名学生，最后resize让数组的长度减1；
friend void remove(vector<student>&a, int row)//删除
{
int msize = a.size();
for (int i = row - 1; i < msize-1; i++)
a[i] = a[i + 1];
a.resize(msize - 1);
cout << setw(10) << "删除成功" << endl;
}
修改，先找到要修改的学生，直接对学生信息进行修改，若修改的函数为为友元函数，需要定义SetValie()和GetValue()的接口
friend void modify(vector<student>& a, int row)//修改
{
cout << "修改人员的完整信息：姓名、性别(male or female)、类别、系别、专业、职称(请用空格隔开每个输入)" << endl;
string mId, mName, mSex, mAge, mClubm, mMajor, mDepartment;
cin >> mId >> mName >> mSex >> mAge >> mClubm >> mMajor >> mDepartment;
a[row-1].SetID(mId); a[row - 1].SetName(mName); a[row - 1].SetSex(mSex);
a[row - 1].SetAge(mAge); a[row - 1].SetMajor(mMajor); a[row - 1].SetDepartment(mDepartment);
cout << "修改成功" << endl;
}
个人查询：直接暴力匹配关键词key就行这里就不演示了
统计：利用map<string，int>统计可以，种类就等于map对应的size()，分别输出的话直接for遍历即可，
friend void stat_sex(vector<student>a)//性别统计
{
map<string, int>num_sex;
for (int i = 0; i < a.size(); i++)
num_sex[a[i].GetSex()]++;
for (auto it : num_sex)
cout << setw(10) << it.first << ":" << it.second << endl;
}
完整源码无bug如下
// I am so vegetable
//made by HRdate,2020-6-29
#include<iostream>
#include<fstream>
#include<vector>
#include<algorithm>
#include<math.h>
#include<string>
#include<iomanip>
#include<set>
#include<map>
#include<conio.h>
using namespace std;
#define endl '\n'
class student
{
public:
//构造函数
student() {};
student(string mid, string mname, string msex, string mage, string mclubm, string mmajor, string mdepartment)
{
id = mid, name = mname, sex = msex, age = mage, clubm = mclubm, major = mmajor, department = mdepartment;
}
//析构函数
~student() {};
//大接口，便于在类外初始化修改类对象的私有变量
void SetInformation(string mid, string mname, string msex, string mage, string mclubm, string mmajor, string mdepartment)
{
id = mid, name = mname, sex = msex, age = mage, clubm = mclubm, major = mmajor, department = mdepartment;
}
//小接口，获取
string GetId() { return id; }
string GetName() { return name; }
string GetSex() { return sex; }
string GetAge() { return age; }
string GetClubm() { return clubm; }
string GetMajor() { return major; }
string GetDepartment() { return department; }
//小接口，赋值
void SetID(string mId) { id = mId; }
void SetName(string mName) { name = mName; }
void SetSex(string mSex) { sex = mSex; }
void SetAge(string mAge) { age = mAge; }
void SetClubm(string mClubm) { clubm = mClubm; }
void SetMajor(string mMajor) { major = mMajor; }
void SetDepartment(string mDepartment) { department = mDepartment; }
//把文本中的数据转化为字符串，通过对字符串空格的处理，使得相应的数据通过SetInformation类接口赋值给vector<student>中的对应的变量
friend void read(string filename, vector<student>& a)
{
fstream file(filename, ios::in | ios::out);
string line;
getline(file, line);
while (!file.eof())
{
student temp;
string str = "", s[10];
int num = 0;
getline(file, line);
for (int i = 0; i < line.size(); i++)
{
if ((line[i] == ' ' || line[i] == '\t') && str != "") {
s[num] = str;
num++;
str = "";
}
else if (line[i] != ' ' && line[i] != '\t')
str += line[i];
}
s[num] = str;
if (s[0] != "" && s[1] != "" && s[2] != "" && s[3] != "" && s[4] != "" && s[5] != "" && s[6] != "")
{
temp.SetInformation(s[0], s[1], s[2], s[3], s[4], s[5], s[6]);
a.push_back(temp);
}
}
file.close();
}
//把修改好的学生信息内容，从vector容器中入读文本，向文本写入
friend void write(string filename, vector<student>a)
{
fstream file(filename, ios::out | ios_base::trunc);
file << "学号"<<'\t'<< "姓名" << '\t' << "性别" << '\t' << "年龄" << '\t' << "班级"
<< '\t' << '\t' << "专业" << '\t' << '\t' << "系别" << endl;
for (int i = 0; i < a.size(); i++)
{
file << a[i].GetId() << '\t' << a[i].GetName() << '\t' << a[i].GetSex() << '\t'
<< a[i].GetAge() << '\t' << a[i].GetClubm() << '\t' << '\t' << a[i].GetMajor()
<< '\t' << '\t' << a[i].GetDepartment() << endl;
}
file.close();
}
//输出显示选定的人员信息
friend void display(vector<student>a)
{
cout << "学号" << '\t' << "姓名" << '\t' << "性别" << '\t' << "年龄" << '\t' << "班级"
<< '\t' << '\t' << "专业" << '\t' << '\t' << "系别" << endl;
for (int i = 0; i < a.size(); i++)
{
cout << a[i].GetId() << '\t' << a[i].GetName() << '\t' << a[i].GetSex() << '\t'
<< a[i].GetAge() << '\t' << a[i].GetClubm() << '\t' << '\t' << a[i].GetMajor()
<< '\t' << '\t' << a[i].GetDepartment() << endl;
}
}
// I am so vegetable
//made by HRdate,2020-6-29
//录入一个学生的信息，new一个student对象，通过SetID等接口可在类外直接定义修改private的成员变量，最后push_back进原容器vector中
friend void input(vector<student>& a)
{
cout << "请输入学生的完整信息：学号、姓名、性别(男 or 女)、年龄、班级、专业、系别(请用空格隔开每个输入)" << endl;
student temp;
string mId, mName, mSex, mAge, mClubm, mMajor, mDepartment;
cin >> mId >> mName >> mSex >> mAge >> mClubm >> mMajor >> mDepartment;
temp.SetID(mId), temp.SetName(mName), temp.SetSex(mSex), temp.SetAge(mAge);
temp.SetClubm(mClubm); temp.SetMajor(mMajor); temp.SetDepartment(mDepartment);
a.push_back(temp);
cout << '\t' << '\t' << "添加成功" << endl;
}
//删除指定学生的信息，从这指定的学生开始，让后一个student赋值给前一个student，往前叠加，最后resize修改一下vector容器大小
friend void remove(vector<student>&a, int row)//删除
{
int msize = a.size();
for (int i = row ; i < msize-1; i++)
a[i] = a[i + 1];
a.resize(msize - 1);
cout << '\t' << '\t' << "删除成功" << endl;
}
//修改指定学生的信息
friend void modify(vector<student>& a, int row)
{
cout << "修改学生的完整信息：学号、姓名、性别(男 or 女)、年龄、班级、专业、系别(请用空格隔开每个输入)" << endl;
string mId, mName, mSex, mAge, mClubm, mMajor, mDepartment;
cin >> mId >> mName >> mSex >> mAge >> mClubm >> mMajor >> mDepartment;
a[row].SetID(mId); a[row].SetName(mName); a[row].SetSex(mSex); a[row].SetAge(mAge);
a[row ].SetClubm(mClubm);a[row ].SetMajor(mMajor); a[row ].SetDepartment(mDepartment);
cout << "修改成功" << endl;
}
//根据学号查询个人
friend int find_id(string key_id, vector<student>a)
{
for (int i = 0; i < a.size(); i++)
if (a[i].GetId() == key_id)
return i;
}
//根据姓名查询个人
friend int find_name(string key_name, vector<student>a)
{
for (int i = 0; i < a.size(); i++)
if (a[i].GetName() == key_name)
return i ;
}
//根据性别查询
friend void find_key_sex(string key_sex, vector<student>a, vector<student>& b)
{
b.clear();
for (int i = 0; i < a.size(); i++)
{
if (a[i].GetSex() == key_sex)
b.push_back(a[i]);
}
//cout << key_sex << "查询成功" << endl;
}
//根据班级查询
friend void find_key_clubm(string key_clubm, vector<student>a, vector<student>& b)
{
b.clear();
for (int i = 0; i < a.size(); i++)
{
if (a[i].GetClubm() == key_clubm)
b.push_back(a[i]);
}
//cout << key_clubm << "查询成功" << endl;
}
//性别统计
friend void stat_sex(vector<student>a)
{
map<string, int>num_sex;
for (int i = 0; i < a.size(); i++)
num_sex[a[i].GetSex()]++;
for (auto it : num_sex)
cout << setw(10) << it.first << ":" << it.second << endl;
}
//班号统计
friend void stat_clubm(vector<student>a)
{
map<string, int>num_clubm;
for (int i = 0; i < a.size(); i++)
num_clubm[a[i].GetClubm()]++;
for (auto it : num_clubm)
cout << setw(10) << it.first << ":" << it.second << endl;
}
//年龄统计
friend void stat_age(vector<student>a)
{
map<string, int>num_age;
for (int i = 0; i < a.size(); i++)
num_age[a[i].GetAge()]++;
for (auto it : num_age)
cout << setw(10) << it.first << ":" << it.second << endl;
}
//系别统计
friend void stat_department(vector<student>a)
{
map<string, int>num_department;
for (int i = 0; i < a.size(); i++)
num_department[a[i].GetDepartment()]++;
for (auto it : num_department)
cout << setw(10) << it.first << ":" << it.second << endl;
}
private:
string id, name, sex, age, clubm, major, department;//学号 姓名 性别 年龄 班级 专业 系别
};
int main()
{
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
string filename = "E:\\text2.txt";//文件名
fstream file(filename, ios::in | ios::out);
if (!file) {
cout << "打开文件失败,请重新输入。" << endl;
return 0;
}
else {
cout << "打开文件成功。" << endl;
}
vector<student>a, b;//vector不定数组存储数据
read(filename, a);
while (1)
{
int check = 0;//菜单选择步骤
string key;//查询关键词
for (int i = 0; i < 70; i++)
cout << '*';
cout << endl;
cout << "*" << setw(32) << "菜单" <<setw(37)<< "*" << endl;
cout << "*" << setw(40) << "输入0：退出系统保存" <<setw(29)<<"*" << endl;
cout << "*" << setw(40) << "输入1：显示当前文本" << setw(29) << "*" << endl;
cout << "*" << setw(40) << "输入2：删除学生信息" << setw(29) << "*" << endl;
cout << "*" << setw(40) << "输入3：修改学生信息" << setw(29) << "*" << endl;
cout << "*" << setw(40) << "输入4：查询个人信息" << setw(29) << "*" << endl;
cout << "*" << setw(40) << "输入5：查询学生信息" << setw(29) << "*" << endl;
cout << "*" << setw(40) << "输入6：统计学生信息" << setw(29) << "*" << endl;
cout << "*" << setw(40) << "输入7：添加学生信息" << setw(29) << "*" << endl;
for (int i = 0; i < 70; i++)
cout << '*';
cout << endl;
cin >> check;
if (check == 0)//退出系统保存
break;
else if (check == 1) {//显示当前文本
display(a);
}
else if (check == 2) //删除学生信息
{
cout << "1：按学号找到删除单个学生信息" << endl << "2:按姓名找到删除单个学生信息" << " (输入0：退出)" << endl;
cin >> check;
if (check == 1)
{
cout << "请输入删除单个学生的学号:" << endl;
cin >> key;
remove(a, find_id(key, a));
}
else if (check == 2) {
cout << "请输入删除单个学生的姓名:" << endl;
cin >> key;
remove(a, find_name(key, a));
}
}
else if (check == 3)//修改学生信息
{
cout << "1：按学号找到修改单个学生信息" << endl << "2:按姓名找到修改单个学生信息" << " (输入0：退出)" << endl;
cin >> check;
if (check == 1)
{
cout << "请输入修改单个学生的学号:" << endl;
cin >> key;
modify(a, find_id(key, a));
}
else if (check == 2) {
cout << "请输入修改单个学生的姓名:" << endl;
cin >> key;
modify(a, find_name(key, a));
}
}
else if (check == 4)//查询个人信息
{
cout << "1：按学号查询单个学生信息" << endl << "2:按姓名找到查询单个学生信息" << " (输入0：退出)" << endl;
cin >> check;
if (check == 1)
{
cout << "请输入查询单个学生的学号:" << endl;
cin >> key;
vector<student>c;
c.push_back(a[find_id(key, a) - 1]);
display(c);
}
else if (check == 2) {
cout << "请输入查询单个学生的姓名:" << endl;
cin >> key;
vector<student>c;
c.push_back(a[find_name(key, a) - 1]);
display(c);
}
}
else if (check == 5)//查询学生信息
{
cout << "1：按性别查询学生信息" << endl << "2:按班号查询学生信息" << " (输入0：退出)" << endl;
cin >> check;
if (check == 1)
{
cout << "请输入查询学生的性别:" << endl;
cin >> key;
vector<student>c;
find_key_sex(key, a, c);
display(c);
}
else if (check == 2)
{
cout << "请输入查询学生的班号:" << endl;
cin >> key;
vector<student>c;
find_key_clubm(key, a, c);
display(c);
}
}
else if (check == 6)//统计学生信息
{
cout << "1：按性别统计学生人数" << endl << "2:按班别统计学生人数" << endl << "3:按年龄统计学生人数" << endl
<< "4:按系别统计学生人数" <<endl<< " (输入0：退出)" << endl;
cin >> check;
if (check == 1)
{
stat_sex(a);
}
else if (check == 2)
{
stat_clubm(a);
}
else if (check == 3)
{
stat_age(a);
}
else if (check == 4)
{
stat_department(a);
}
}
else if (check == 7)//添加学生信息
{
input(a);
}
//getchar();
// system("cls"); 清屏
}
write(filename, a);
file.close();
return 0;
}