Array of objects inside a class

Question

So, I have two classes: Node and Graph. In the private section of Graph class I declare this:

int size;
Node* n;

In the Graph constructor I'm trying to create a dynamic array:

size=1;

Node *n = new Node[size];

But I'm getting an error: "Access violation reading location 0xcccccd44". How can I fix it? I know that I must be doing something wrong with the array, but I have no idea what and how to fix it.

Class Graph:

class Graph {
    friend class Node;

    private:
        int size;
        Node* n;

    public:
        Graph();
        Graph(int, Vertex*);
        ~Graph();
        void Draw(RenderWindow &);
        void Update(RenderWindow &, GameObject &, bool);
};

And two constructors:

Graph::Graph() {
    size=1;

    Node *n = new Node[size];
}

Graph::Graph(int s, Vertex p[]) {
    size=s;
    Node *n = new Node[size];
    for (int i=0; i<size; i++) {
        n[i].setNumer(i);
        n[i].setX(p[i].getX());
        n[i].setY(p[i].getY());
    }
}

You need to post more code, but I would guess you are not following the rule of three. — juanchopanza
– juanchopanza, Commented Nov 26, 2013 at 15:03
Well, there's really not much more code to add here... I'll put the code in the first post. — mentor93
– mentor93, Commented Nov 26, 2013 at 15:04
Did you mean to initialise the member n, rather than declaring a local variable with the same name? And why aren't you using std::vector<Node> to avoid all the problems you get with manual pointer-juggling? — Mike Seymour
– Mike Seymour, Commented Nov 26, 2013 at 15:05
Shouldn't that be n = new Node[size];, you are hiding your member variable n. — Shafik Yaghmour
– Shafik Yaghmour, Commented Nov 26, 2013 at 15:06

john · Accepted Answer · 2013-11-26 15:06:57Z

2

You are redeclaring n in your constructor. You got it right with size but not with n. Like this

Graph::Graph(int s, Vertex p[]) {
    size=s;
    n = new Node[size];
    for (int i=0; i<size; i++) {
        n[i].setNumer(i);
        n[i].setX(p[i].getX());
        n[i].setY(p[i].getY());
    }
}

In your version you are initializing a local variable called n, which is different to the n declared in your class.

answered Nov 26, 2013 at 15:06

john

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Comments

Shafik Yaghmour · Accepted Answer · 2013-11-26 15:09:40Z

0

As I mentioned in my comment before you posted the rest of your code, you are hiding your member variable n here:

Node *n = new Node[size];
^^^^^^^

this declares a new automatic variable n which will not exist after you leave your constructor and will also leak memory, just change it to this:

n = new Node[size];

As others already mentioned using std::vector would be easier.

answered Nov 26, 2013 at 15:09

Shafik Yaghmour

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