Add file_with_class.cpp

file_with_class.cpp

@@ -0,0 +1,67 @@
+#include <iostream>
+#include <fstream>
+#include <string>
+using std::cin, std::cout, std::string;
+
+class Student
+{
+    string name;          // 学生姓名
+    int course_num;       // 学生课程数
+    int *score;           // 指向动态分配成绩数组
+    const char *filename; // 用来处理读写文件的名字
+
+public:
+    Student(string _name, int _course_num, const char *_filename)
+        : name{_name}, course_num{_course_num}, filename{_filename}
+    {
+        score = new int[course_num]{};
+        cout << "请依次输入" << course_num << "门课的成绩：";
+        for (int i = 0; i < course_num; ++i)
+            std::cin >> score[i];
+    }
+
+    Student(const char *_filename) : filename{_filename}
+    {
+        std::ifstream infile(filename, std::ios::in | std::ios::binary);
+        if (infile)
+        {
+            int len{};
+            infile.read(reinterpret_cast<char *>(&len), sizeof(int));
+            char *buffer = new char[len + 1]{};
+            infile.read(buffer, len);
+            name = buffer;
+            delete[] buffer;
+            infile.read(reinterpret_cast<char *>(&course_num), sizeof(course_num));
+            score = new int[course_num]{};
+            infile.read(reinterpret_cast<char *>(score), course_num * sizeof(int));
+            infile.close();
+        }
+    }
+    ~Student()
+    {
+        std::ofstream ofile(filename, std::ios::out | std::ios::binary);
+        {
+            int len{static_cast<int>(name.size())};
+            ofile.write(reinterpret_cast<char *>(&len), sizeof(len));
+            ofile.write(name.c_str(), len);
+            ofile.write(reinterpret_cast<char *>(&course_num), sizeof(course_num));
+            ofile.write(reinterpret_cast<char *>(score), course_num * sizeof(int));
+            ofile.close();
+            delete[] score;
+        }
+    }
+    friend std::ostream &operator<<(std::ostream &os, Student &s)
+    {
+        os << "姓名：" << s.name << " 成绩：";
+        for (int i{0}; i < s.course_num; ++i)
+            os << s.score[i] << '\t';
+        return os << '\n';
+    }
+};
+
+int main()
+{
+    Student s1{"TOM", 5, "s1.dat"};
+    // Student s1{"s1.dat"}; 这句话和上面的语句分两次运行即可
+    cout << s1;
+}