如何在 C++ 中搜索对象名称

Question

希望大家度过了美好的一天！

我的问题是我不知道如何搜索对象的名称（如果那是正确的放置方式）。但是一个例子是：我创建了一个包含名字、姓氏、年级和出生年份的学生班级。其中一名学生的名字可能是“艾萨克”。我想要做的是在“命令提示符”中写一个名字，结果应该是我写的学生姓名的信息。如果名字没有被列为学生之一，我应该可以再试一次。

下面是我的小代码。在“search_after_student_name”中应该是计算机搜索学生的名字以查看该学生信息的地方。

#include <iostream>
#include <Windows.h>
#include <cstring>
using namespace std;

class Student {
public:
    string first_name;
    string last_name;
    char grade;
    int birth;
    Student(string aFirst_name, string aLast_name, char aGrade, int aBirth) {
        first_name = aFirst_name;
        last_name = aLast_name;
        grade = aGrade;
        birth = aBirth;
    }
};

void search_after_student_name(string hisFirst_name)
{
    
    if (hisFirst_name != student.first_name) //Is not like that, but just an example of how I am going to use it
        cout << "We couldn't find the name you wrote. Try again" << endl;
    else() //if the "hisFirst_name" matches a student:
    {
        cout << "info about this student...";
    }
}

int main()
{
    SetConsoleCP(1252);
    SetConsoleOutputCP(1252);

    Student student1("Oliver", "Twist", 'C', 1999);
    Student student2("James", "Free", 'D', 2000);
    Student student3("Isaac", "Lee", 'A', 2000);

    string namn;
    cout << "Write in the name that you want to search: ";
    cin >> namn;

    search_after_student_name(namn);
    return 0;
} 

我希望你能理解我的愚蠢代码问题并帮助我。谢谢！

Answer 1

正如 cmets 中所指出的，您应该使用一些数据结构来保存您的数据。这可能是一个解决方案：

#include <iostream>
#include <Windows.h>
#include <string>
#include <vector>
#include <algorithm>

using namespace std;

class Student
{
public:
    string first_name;
    string last_name;
    char grade;
    int birth;
    Student(string aFirst_name, string aLast_name, char aGrade, int aBirth)
    {
        first_name = aFirst_name;
        last_name = aLast_name;
        grade = aGrade;
        birth = aBirth;
    }
};

void search_after_student_name(const string& hisFirst_name, const std::vector<Student>& students)
{
    auto studentIt = std::find_if(std::begin(students), std::end(students), [&hisFirst_name](const auto & s)
    {
        return s.first_name == hisFirst_name;
    });

    if (studentIt == std::end(students)) 
        cout << "We couldn't find the name you wrote. Try again" << endl;
    else //if the "hisFirst_name" matches a student:
    {
        cout << "info about this student: ";
        cout << studentIt->first_name << ", "
             << studentIt->last_name << ", "
             << studentIt->grade << ", "
             << studentIt->birth;
    }
}

int main()
{
    SetConsoleCP(1252);
    SetConsoleOutputCP(1252);

    std::vector<Student> students =
    {
        Student("Oliver", "Twist", 'C', 1999),
        Student("James", "Free", 'D', 2000),
        Student("Isaac", "Lee", 'A', 2000),
    };

    string namn;
    std::cout << "Write in the name that you want to search: ";
    std::cin >> namn;

    search_after_student_name(namn, students);
    return 0;
}

请注意，我将search_after_student_name 更改为通过const reference 获取数据，如果您不需要更改数据，这是better way 将数据传递给您的函数。

Answer 2

请注意，数据集合应存储在数组或其他类型的容器中。 另外为了保持代码干净，这里应该使用标准算法，为了练习 C++20，已经使用了std::ranges::find（我也清理了一些样板）：

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <ranges>

class Student
{
public:
    std::string first_name;
    std::string last_name;
    char grade;
    int birth;
};

void printStudent(const Student& x)
{
    std::cout << "first_name: " << x.first_name << '\n';
    std::cout << " last_name: " << x.last_name << '\n';
    std::cout << "     grade: " << x.grade << '\n';
    std::cout << "     birth: " << x.birth << '\n';
}

int main()
{
    std::vector students {
        Student{"Oliver", "Twist", 'C', 1999},
        {"James", "Free", 'D', 2000},
        {"Isaac", "Lee", 'A', 2000},
    };

    std::string name;
    std::cout << "Write in the name that you want to search: ";
    std::cin >> name;

    auto it = std::ranges::find(students, name, &Student::first_name);
    if (it == students.end()) {
        std::cout << "\nNot found\n";
    } else {
        std::cout << "\nStudent found:\n";
        printStudent(*it);
    }
    return 0;
}

https://godbolt.org/z/GdafW9Yjv