在 C++ 中使字符串变量成为类名

Question

I'm working on a program in C++ to make schedules for me, since I have a hard time focusing on school work. The code will make priorities of assignments based on the due dates, duration to do the assignments, etc.

Anyway, I've run into a massive problem. I'm trying to assign a class variable's name to a variable! For example:

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

If you don't think this way will work, please tell me other solutions!

Also, I'm still a beginner, so please try to explain a little simple!

---

Here's the code:

#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

What you are looking for is an array of Assignment objects, eg:

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;
}

Though, you should use std::vector instead of new[] directly:

#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;
}

Or:

#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

The compiler does not emit symbol names to the executable (the debug version may have symbol names).

If you want to associate or map symbol names to variables, you will need to declare the variable global and place the address into some kind of table.

Example:

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;

You may want to give deep thought to the need of retaining variable names.