使用unique_ptr作为成员类并带有list

Question

我最近做了一个有1个超类和2个子类的应用程序。它的主要思想是将信息存储在3个不同的列表中。我的问题是，你可以只使用一个列表的所有3类?尽管这两个子类有一些额外的成员。有人告诉我，你可以使用unique_ptr作为超类的成员，并且只生成一个列表。我在网上看到过，但是我不太明白。有什么建议吗?谢谢你的宝贵时间。

class Student {
std::string Name;
std::string Pinfo;
std::map < std::string, float > Ngradelist;
public:
std::string getName() {return Name;}
std::string getPinfo() {return Pinfo;}
virtual void InsertGradeList(std::string a, float b) {
for(auto& it : Ngradelist)
Ngradelist.insert(std::pair <std::string, float > (a,b));
}
Student( std::string n,  std::string p, std::map < std::string, float > Ng) :
Name(std::move(n)), Pinfo(std::move(p)), Ngradelist(std::move(Ng)) {}
virtual void Display() {
std::cout << "Name: " << Name << std::endl;
std::cout << "Personal information: " << Pinfo << std::endl;
std::cout << "NCourse:" << std::endl;
for(auto& it : Ngradelist)
std::cout << "   " << it.first << "   Grade: " << it.second <<  std::endl;
}
};
class HWStudent : public Student {
std::string FieldOfWork;
std::map<std::string, float> HWgradelist;
public:
void InsertGradeList(std::string a, float b) override{
for (auto &it : HWgradelist)
HWgradelist.insert(std::pair<std::string, float>(a, b));
}
HWStudent(std::string n, std::string p, std::map<std::string, float> Ng, std::string f,
std::map<std::string, float> HWg) : Student(std::move(n), std::move(p), std::move(Ng)),
FieldOfWork(std::move(f)), HWgradelist(std::move(HWg)) {}
void Display() override {
Student::Display();
std::cout << "Field of Work: " << FieldOfWork << std::endl;
std::cout << "HWCourse:" << std::endl;
for(const auto& it : HWgradelist)
std::cout << "   " << it.first << "   Grade: " << it.second <<  std::endl;
}
};
class SWStudent : public Student {
std::map<std::string, float> SWgradelist;
std::list < std::string > Languages;
public:
void InsertGradeList(std::string a, float b) override {
for (const auto &it : SWgradelist)
SWgradelist.insert(std::pair<std::string, float>(a, b));
}
SWStudent(std::string n, std::string p, std::map<std::string, float> Ng, std::list < std::string > l,
std::map<std::string, float> SWg) : Student(std::move(n), std::move(p), std::move(Ng)),
Languages(std::move(l)), SWgradelist(std::move(SWg)) {}
void Display() override {
Student::Display();
std::cout << "SWCourse:" << std::endl;
for(const auto& it : SWgradelist)
std::cout << "   " << it.first << "   Grade: " << it.second <<  std::endl;
std::cout << "SW Languages:" << std::endl;
for(const auto& it : Languages)
std::cout << "   " << it << std::endl;
}
};
std::list < Student > listaStudenti;
std::list < HWStudent > HWlistaStudenti;
std::list < SWStudent > SWlistaStudenti;
void InsertListaStudenti(unsigned short option) {
unsigned short numbers;
std::string name , pinfo, course, fieldofwork, hwcourse, swcourse;
std::string language;
float grade = 0, hwgrade, swgrade;
std::list < std::string > languagelist;
if(option == 1) {
std::cout << "Insert name: ";
std::cin >> name;
std::cout << "Insert personal information: ";
std::cin >> pinfo;
std::cout << "Insert course: ";
std::cin >> course;
std::cout << "Insert grade: ";
std::cin >> grade;
Student student(name, pinfo, {{course, grade}});
listaStudenti.push_back(student);
}
if(option == 2) {
std::cout << "Insert name: ";
std::cin >> name;
std::cout << "Insert personal information: ";
std::cin >> pinfo;
std::cout << "Insert course: ";
std::cin >> course;
std::cout << "Insert grade: ";
std::cin >> grade;
std::cout << "Insert hwcourse: ";
std::cin >> hwcourse;
std::cout << "Insert hwgrade: ";
std::cin >> hwgrade;
std::cout << "Insert fieldofwork: ";
std::cin >> fieldofwork;
HWStudent hwstudent(name, pinfo, {{course, grade}}, fieldofwork,{{hwcourse, hwgrade}});
HWlistaStudenti.push_back(hwstudent);
}
if(option == 3) {
std::cout << "Insert name: ";
std::cin >> name;
std::cout << "Insert personal information: ";
std::cin >> pinfo;
std::cout << "Insert course: ";
std::cin >> course;
std::cout << "Insert grade: ";
std::cin >> grade;
std::cout << "Insert swcourse: ";
std::cin >> swcourse;
std::cout << "Insert swgrade: ";
std::cin >> swgrade;
std::cout << "How many  languages: ";
std::cin >> numbers;
for(auto it = 0;it < numbers; ++it) {
std::cout << "Insert language: ";
std::cin >> language;
languagelist.push_back(language);
}
SWStudent swstudent(name, pinfo, {{course, grade}},languagelist,{{swcourse, swgrade}});
SWlistaStudenti.push_back(swstudent);
}
}
int main() {
unsigned short option = 10;
while(option != 0) {
std::cout << "1.Add student." << std::endl;
std::cout << "2.Add HW student." << std::endl;
std::cout << "3.Add SW student." << std::endl;
std::cout << "4.Display Student." << std::endl;
std::cout << "5.Display HW Student." << std::endl;
std::cout << "6.Display SW Student." << std::endl;
std::cout << "0 is for exit." << std::endl;
std::cout << "Option is : ";
std::cin >> option;
switch  (option) {
case 0 : {
std::cout <<" You chose to leave.";
exit;
break;
}
case 1 : {
InsertListaStudenti(option);
break;
}
case 2 : {
InsertListaStudenti(option);
break;
}
case 3: {
InsertListaStudenti(option);
break;
}
case 4: {
for(auto &it : listaStudenti)
it.Display();
break;
}
case 5: {
for(auto &it : HWlistaStudenti)
it.Display();
break;
}
case 6: {
for(auto &it : SWlistaStudenti)
it.Display();
break;
}
}
}
}

Answer 1

您确实可以使用

std::list<std::unique_ptr<Student>> students;

不是

std::list<Student> listaStudenti;
std::list<HWStudent> HWlistaStudenti;
std::list<SWStudent> SWlistaStudenti;

• 插入类似于

  Student student(name, pinfo, {{course, grade}});
  students.push_back(std::make_unique<Student>(std::move(student)));
  // or std::make_unique<Student>(name, pinfo, std::map<std::string, float>{{course, grade}})
  HWStudent hwstudent(name, pinfo, {{course, grade}}, fieldofwork, {{hwcourse, hwgrade}});
  students.push_back(std::make_unique<HWStudent>(std::move(hwstudent));
  

  不是

  Student student(name, pinfo, {{course, grade}});
  listaStudenti.push_back(student);
  HWStudent hwstudent(name, pinfo, {{course, grade}}, fieldofwork,{{hwcourse, hwgrade}});
  HWlistaStudenti.push_back(hwstudent);
  

• 问题是你的"过滤"

  for (auto& student : SWlistaStudenti) {
  student.Display();
  }
  

  是

  for (auto& studentPtr : SWlistaStudenti) {
  if (auto ptr = dynamic_cast<SWStudent*>(studentPtr.get())) ptr->Display();
  }
  

  but(只显示普通学生(不包括HW/SW))

  for(auto& student : listaStudenti) { student.Display(); }
  

  是

  for (auto& studentPtr : students) {
  if (!dynamic_cast<SWStudent*>(studentPtr.get())
  && !dynamic_cast<HWStudent*>(studentPtr.get())) {
  studentPtr->Display();
  }
  }
  

• 一个列表允许平等对待它们:

  显示所有学生:

  for (auto& studentPtr : students) { studentPtr->Display(); }
  

  不是

  for (auto& student : listaStudenti) { student.Display(); }
  for (auto& student : HWlistaStudenti) { student.Display(); }
  for (auto& student : SWlistaStudenti) { student.Display(); }