在 C++ 中使字符串变量成为类名

Question

我正在用 C++ 编写一个程序来为我制定时间表，因为我很难专注于学校工作。 该代码将根据截止日期、完成任务的持续时间等确定任务的优先级。

无论如何，我遇到了一个大问题。 我正在尝试将类变量的名称分配给变量！ 例如：

string a = "assignmentName" Class a(); //a is a variable and it's supposed to put the class's name as assignmentName

如果您认为这种方式行不通，请告诉我其他解决方案！

另外，我还是一个初学者，所以请尽量解释得简单一点！

---

这是代码：

#include <string>
#include <iostream>
using namespace std;

class Assignment
{
  private:
    int duration = 30; //Amount of time per assignment (in minutes)
    int due = 1; //Amount of days till its due, if it's one then the assignment is due in 1 days
    string name; //Name of assignment
  public:
    Assignment(int, int, string);
    ~Assignment();

    void setDuration(int duration) {this -> duration = duration;}
    void setDue(int due) {this -> due = due;}
    void setDue(int name) {this -> name = name;}

    int getDuration() { return duration; }
    int getDue() { return due; }
    string getName() { return name; }
};

Assignment::Assignment (int duration, int due, string name) //Constructor Method
{
  this -> duration = duration;
  this -> due = due;
  this -> name = name;
}

Assignment::~Assignment() //Destructor Method
{
  cout << "Assignment Object Destroyed" << endl;
}

int main()
{
  int assignmentAmount;
  int i;
  int userInput1;
  int userInput2;
  string userInput3;


  cout << "Enter assignment amount: ";
  cin >> assignmentAmount << "\n" << endl;

  for (i = 0; i < assignmentAmount; i++){
    cout << "Enter assignment" << i <<"'s " << "duration: ";
    cin >> userInput1 << endl;

    cout << "Enter assignment" << i << "'s " << "due date in days from now: ";
    cin >> userInput2 >> endl;

    cout << "Enter assignment" << i <<"'s " << "name: ";
    cin >> userInput3 >> endl;

    Assignment i(userInput1, userInput2, userInput3); //I is the class's number and it's supposed to be a variable
  }

  return 0;
}

Answer 1

您正在寻找的是一组Assignment对象，例如：

int main()
{
  Assignment *assignments;
  int assignmentAmount;
  int userInput1;
  int userInput2;
  string userInput3;

  cout << "Enter assignment amount: ";
  cin >> assignmentAmount << "\n" << endl;

  assignments = new Assignment[assignmentAmount];

  for (int i = 0; i < assignmentAmount; i++){
    cout << "Enter assignment " << i << "'s duration: ";
    cin >> userInput1 << endl;

    cout << "Enter assignment " << i << "'s due date in days from now: ";
    cin >> userInput2 >> endl;

    cout << "Enter assignment " << i <<"'s name: ";
    cin >> userInput3 >> endl;

    // either:
    assignments[i] = Assignment(userInput1, userInput2, userInput3);

    // or:   
    assignments[i].setDuration(userInput1);
    assignments[i].setDue(userInput2);
    assignments[i].setName(userInput3);
  }

  // use assignments and assignmentAmount as needed...

  delete[] assignments;

  return 0;
}

不过，您应该直接使用std::vector而不是new[] ：

#include <vector>
...

int main()
{
  std::vector<Assignment> assignment;
  int assignmentAmount;
  int userInput1;
  int userInput2;
  string userInput3;

  cout << "Enter assignment amount: ";
  cin >> assignmentAmount << "\n" << endl;

  for (int i = 0; i < assignmentAmount; i++){
    cout << "Enter assignment " << i << "'s duration: ";
    cin >> userInput1 << endl;

    cout << "Enter assignment " << i << "'s due date in days from now: ";
    cin >> userInput2 >> endl;

    cout << "Enter assignment " << i << "'s name: ";
    cin >> userInput3 >> endl;

    // either:
    assignments.push_back(Assignment(userInput1, userInput2, userInput3));

    // or:
    assignments.emplace_back(userInput1, userInput2, userInput3);
  }

  // use assignments as needed...

  return 0;
}

或者：

#include <vector>
...

int main()
{
  std::vector<Assignment> assignment;
  int assignmentAmount;
  int userInput1;
  int userInput2;
  string userInput3;

  cout << "Enter assignment amount: ";
  cin >> assignmentAmount << "\n" << endl;

  assignments.resize(assignmentAmount);

  for (int i = 0; i < assignmentAmount; i++){
    cout << "Enter assignment " << i << "'s duration: ";
    cin >> userInput1 << endl;

    cout << "Enter assignment " << i << "'s due date in days from now: ";
    cin >> userInput2 >> endl;

    cout << "Enter assignment " << i << "'s name: ";
    cin >> userInput3 >> endl;

    // either:
    assignments[i] = Assignment(userInput1, userInput2, userInput3);

    // or:
    assignments[i].setDuration(userInput1);
    assignments[i].setDue(userInput2);
    assignments[i].setName(userInput3);
  }

  // use assignments as needed...

  return 0;
}

Answer 2

您无法将变量名作为变量获取，因为变量基本上就像数据的别名，当您的程序被编译时，所有这些名称不再存在。

Answer 3

编译器不会向可执行文件发出符号名称（调试版本可能有符号名称）。

如果要将符号名称关联或映射到变量，则需要将变量声明为 global 并将地址放入某种表中。

例子：

int my_global_int_a;
std::map<std::string, int *> variable_dictionary;
variable_dictionary["my_global_int_a"] = &my_global_int_a;
// Here's how to get the variable
const std::string variable_name = "my_global_int_a";
int * p_variable = nullptr;
p_variable = variable_dictionary[variable_name];
std::cout << *p_variable << std::endl;

您可能需要深入考虑保留变量名称的必要性。