在C ++中用堆创建结构数组

Question

I need to declare an array of structures on the heap, then transfer data from parallel arrays on the stack and from calculations into each structure. I declared

struct Grades
{
    string  studentName;
    int     scores[4];
    double  average;
};

....

Grades *art1301 = new Grades;

....

(art1301 + i)->studentName = names[i];

for((int i = 0 ; i < 5 ; i++ )
(art1301 + i)->scores[j] = exams[i][j];

(art1301 + i)->average = average; 

My program accesses the first record, but it crashes after it accesses the first field of the second record. I don't understand why it works for the first record, but dies in the middle of the second? Am I accessing the structure correctly?

Thank you.

Answer 1

To allocate an array, you need the array form of new , with the square brackets:

Grades *art1301 = new Grades[200];
//                          ^^^^^

The array size can be a dynamically determined quantity.

Answer 2

You aren't allocating memory for an array, you are allocating only for one element.

As someone said in the comments, the key is in the new Grades instruction

In addition, unless you have another i variable declared before (which is a bad practice), that code doesn't compile because (art1301 + i)->studentName = names[i]; will not find variable i