How to make a class variable array

Question

How do I create an array of a grade class variable. I don't understand how to initialize and what to write in main(). from this, is there a way to make a constant? And do I need a for loop to read and output the array? Thanks

class First
{
  public:
    int getId();
    void setId(int);
    int getExam();
    void setExam(int);
    void print();
    First(int studentId, int exam);

  private:
    int id;
    int grade;
};

int main()
{
  int studentId = 0;
  int exam = 0;

  First Student(studentId, exam);

  cout << "Enter student id" << endl;
  cin >> studentId;
  Student.setId(studentId);

  cout << "enter grade" << endl;
  cin >> exam;
  Student.setExam(exam);

  Student.print();

  return 0;

}

You declare an array as a class member variable the same way you declare an array anywhere else, such as a local or global variable. — Code-Apprentice
– Code-Apprentice, Commented May 22, 2013 at 23:19

David G · Accepted Answer · 2013-05-23 19:15:15Z

3

If you know the size of the array at compile-time, this is how you would create the array:

First student_list[size];

Though it's more ideal to use compile-time classes like std::array<T, N>:

#include <array>

std::array<int, size> student_list;

If you don't know the size at compile-time, or your compiler doesn't support std::array, use std::vector<T>:

#include <vector>

std::vector<int> student_list;

Moreover, your parameterized constructor (First(int, int)) overrides the default and copy-constructor that the compiler normally provides. Your default constructor can look like this:

First() { }

Otherwise you can use the default specifier with C++11:

First() = default;

However, by using default parameters for your specialized constructor, it can act as a default constructor when given 0 arguments. The following is a good alternative:

First(int studentid = 0, int exam = 0)
{ }

And lastly, yes, you would need some sort of loop to print out each element's grade in succession.

edited May 23, 2013 at 19:15

answered May 22, 2013 at 23:25

David G

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3 Comments

Keith Over a year ago

Also: Need a default constructor, and possibly a copy constructor.

David G Over a year ago

@user1787000 As Keith said, you will also need to implement a default constructor and a copy constructor, otherwise when you create the array you will get errors because it default constructs each element.

pmr Over a year ago

+1, but I really disagree with the default arguments for the constructor. It is now also a implicitly converting constructor, which is really unfortunate. I'd rather write a default constructor and delegate.

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