Initialize pointer to array

Question

I am trying to initialize pointer to struct array in my class constructor but it do not working at all...

class Particles {

private:

    struct Particle {
        double x, y, z, vx, vy, vz;
    };

    Particle * parts[];

public:

    Particles (int count)
    {
        parts = new Particle [count]; // < here is problem
    }

};

That's not a pointer to an array, that's an array of pointers to `Particle`. See [this](http://stackoverflow.com/questions/10252837/pointer-to-array-c). — m0skit0, Mar 21 '13 at 16:43
You could save yourself a lot of trouble by using an `std::vector` instead of the dynamically allocated array. — juanchopanza, Mar 21 '13 at 16:52

masoud · Accepted Answer · 2013-03-21T16:50:59.620

6

Remove those [] from declaration. It should be

Particle *parts;

Using C++, you can use benefits of std::vector:

class Particles {
  // ...

 std::vector<Particle> parts;

 public:

    Particles (int count) : parts(count)
    {

    }
};

edited Mar 21 '13 at 16:50

answered Mar 21 '13 at 16:42

masoud

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@balki no, because `count` is not a compile time constant. But `std::vector` would do fine. – juanchopanza Mar 21 '13 at 16:50

score 2 · Answer 2 · answered Mar 21 '13 at 16:43

Particle * parts[];

This is an array of pointers. To initialise this, you would need to loop through the array, initialising each of the pointers to point at a dynamically allocated Particle object.

You probably want to just make parts a pointer:

Particle* parts;

The new[] expression returns a pointer to the first element of the array - a Particle* - so the initialisation will work just fine.

score 1 · Answer 3 · answered Mar 21 '13 at 16:45

1

Try this:

class Particles {

private:

struct Particle {
    double x, y, z, vx, vy, vz;
};

Particle * parts;

public:

Particles (int count)
{
    parts = new Particle [count]; // < here is problem
}

};

answered Mar 21 '13 at 16:45

Leo Chapiro

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Initialize pointer to array

3 Answers3