CODEWITHSUNDEEP
c++arrayspointers
Jan SE
Jan SE

Reputation: 427

initialize array in constructor

I want to have a class which has a member array. The size of the array should be given when I initialize the object. I just found a way with pointers to do this. I think it is working correctly, but can you maybe tell me if this is the best way to do it or if there are any things which do not work which I haven't recognized yet?

#include <iostream>
using namespace std;

class Surface {
  private:
    float dx;
    int N;
    float* mesh_points;

  public:
    Surface(float, int);
    ~Surface();
    void set_dx (float);
    float get_dx();
};

Surface::Surface(float dx,int N){
  this->dx = dx;
  this ->N = N;
  mesh_points = new float[N];
}


void Surface::set_dx (float dx) {
  this->dx = dx;
}


float Surface::get_dx (void) {
  return dx;
}

Surface::~Surface(){
  delete[] mesh_points;
}

int main () {
  Surface s(1.2,10);
  s.set_dx (3.3);
  cout << "dx: "<< s.get_dx() <<endl;

  float mesh_points[3];
  return 0;
}

Upvotes: 0

Views: 113

Answers (2)

Bartek Banachewicz
Bartek Banachewicz

Reputation: 39370

can you maybe tell me if this is the best way to do it or if there are any things which do not work which I haven't recognized yet?

That'd be my take basing on existing best practices:

class Surface {
private:
    std::vector<float> mesh_points;

public:
    float dx;

    Surface(float dx, std::size_t n);
};

Surface::Surface(float dx, std::size_t n)
  : dx(dx)
  , mesh_points(n)
{
}

In short, the changes made:

Please note that the current interface doesn't allow any access to mesh_points.

Upvotes: 5

john
john

Reputation: 87944

Here's an alternative suggestion that allows you to keep your current implementation but is a lot safer.

class Surface {
  private:
    float dx;
    int N;
    float* mesh_points;

  public:
    Surface(float, int);
    ~Surface();
    void set_dx (float);
    float get_dx();
    Surface(const Surface&) = delete;            // new
    Surface& operator=(const Surface&) = delete; // new
};

By deleting the implementation of the copy constructor and copy assignment operator you prevent your Surface objects from being copied (which would likely crash your program anyway). Any attempt to copy Surface objects will now result in a compile time error.

Only a suggestion, my first choice would always be to use std::vector.

Upvotes: 0

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