Initializing an array of pointers to a defined structure with constructor

Question

struct Mystruct
{
  int x;
  int y;
  Mystruct(int x, int y);
}
------------------------
class Myclass
{
  Mystruct** p;
  Myclass(int n);
}
------------------------
Myclass::Myclass(int n)
{
  this->p = new Mystruct*[n];
  for ( int i = 0; i < n; i++ )
    this->p[i] = new Mystruct[n];
}

This will not work. I know the problem lies somewhere with default constructor not being available, but I do not know how to move forward from here.

this->p[i] is not an array pointer. try this->p[I] = new MyClass(); — samk
– samk, Commented Apr 23, 2020 at 10:48
First things first, i'll give the obligatory std::vector<std::vector<Mystruct>> p (n, std::vector<Mystruct>(n)); would be much safer and avoid manual memory management. Anyway, it's unclear to me what you want all the Mystruct to contain in terms of data. — George
– George, Commented Apr 23, 2020 at 10:49
I repaired it to this->p. @George It is a school project related where we are not allowed to use vectors. In Mystruct I want to have two integers x and y with information about a predescor on a chessboard. — Milan
– Milan, Commented Apr 23, 2020 at 10:52

bruno · Accepted Answer · 2020-04-23 11:09:30Z

2

you want

Myclass::Myclass(int n)
{
  this->p = new Mystruct*[n];
  for ( int i = 0; i < n; i++ )
    this->p[i] = new Mystruct[n];
}

because Mystruct** p;

You also need to save the dimension, and to add a destructor, very probably the constructor must be public.

As said in a remark to be able to allocate your array of Mystruct that one need a constructor without parameter

edited Apr 23, 2020 at 11:09

answered Apr 23, 2020 at 10:53

bruno

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3 Comments

WhozCraig Over a year ago

...and a default ctor to Mystruct, or that inner array-allocation is doomed.

Milan Over a year ago

Thank you guys, it seems that all the warnings evaporated as I wrote a default constructor. Is it ok to have an empty default constructor in this situation set as Mystruct::Mystruct(){} ?

bruno Over a year ago

@Milan yes else impossible to do new Mystruct[n];

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