Copy Constructor Pointer Object

Question

I have the following class with the 2 pointers to block

#ifndef SCORING_H
#define SCORING_H

#include "Block.h"
#include <iostream>
#include <vector>
#include <cstring>

using namespace std;

class Scoring
{
    public:
        Scoring(Block *, Block*, string, string, double);
        virtual ~Scoring();
        Scoring(const Block& b1, const Block &b2);
    private:
        Block * b1;
        Block * b2;
        string path1;
        string path2;
        double val;
};

#endif // SCORING_H

Class Block is the following:

class Block {
    public :
        ///constructo
        Block(double, double, double, double, int, vector<LineElement*>);

        ///Setter functions
        void setID(int);
        void setTop(double);
        void setLeft(double);
        void setRight(double);
        void setBottom(double);
        void setLine(vector<LineElement*>);

        int getID();
        double getTop();
        double getLeft();
        double getBottom();
        double getRight();
        vector<LineElement*> getLine();

    private:
        int id;
        vector<LineElement*> Listline;
        double top;
        double left;
        double bottom;
        double right;
};

#endif // ELEMENT_H_INCLUDED

I want to know, Should I construct a copy constructor for "Block * b1;Block * b2" and how can I treat these 2 points in the class scoring.h?

Thank you.

I'm guessing that Block::getLine just returns the ListLine? Remember that this will cause the whole vector top be copied which might not be what you want. You should probably return a reference instead, e.g. vector<LineElement*>& getLine();. If you don't want the callers to modify the vector then make it const (as well as the getLine function). — Some programmer dude
– Some programmer dude, Commented May 30, 2013 at 13:13

Some programmer dude · Accepted Answer · 2013-05-30 13:07:56Z

1

If you create a constructor other than plain and simple Block::Block(const Block&) then it's not a copy-constructor. If you want to make a constructor in Scoring taking two Block pointers it's most definitely is not a copy-constructor.

If you want a copy-constructor in Scoring it should be like this:

class Scoring
{
    // ...

    Scoring(const Scoring& other);

    // ...
};

Then in that constructor you copy from other:

Scoring::Scoring(const Scoring& other)
    : b1(new Block(*other.b1)),
      b2(new Block(*other.b2)),
      path1(other.path1),
      path2(other.path2),
      val(other.val)
{
}

Of course, you should probably make a copy-constructor for the Block class too, as it contains a vector of pointers, and if you don't you will have two vectors with pointers pointing to the same objects, and that will be bad when you delete these objects in one vector but not the other.

answered May 30, 2013 at 13:07

Some programmer dude

411k36 gold badges421 silver badges655 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Hani Goc Over a year ago

Ok i see. I just have this question. Am I forced as a rule to create a copy constructor when i have pointers? and in my case was it important to use it?

Some programmer dude Over a year ago

@HaniGoc If you create the pointers in the object, then yes having a copy constructor is a must unless you want to have dangling pointers. I suggest you read about the rule of three.

Collectives™ on Stack Overflow

Copy Constructor Pointer Object

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related