Initializing array of objects

Question

I want to initialize an array. There's no compilation error but when I run the program it shows the first cout then stop running.

Here's my code:

class A {
    string first_name ;
    string last_name;
    int ID;
public:
    virtual void print ()=0;
};

class B :public A{
    string phone_number;

    .......
    void print(){
        ........
    }
};

class D{
    A** a;
    int size;
public:
    D(){
        size = 10;
        a = new A *[size];
        for(int i = 0 ; i<size ; i++){
            a[i] = NULL;
        }
    }

    void Add(){
        for(int i = 0 ; i<size ; i++){
            A * a2 = a[i];
            B * b  = dynamic_cast<B*>(a2);
            int id;
            cout<<"enter the id";
            cin>>id
            b->set_ID(id);
            // i did the same (cout , cin statements) for the first name and last name.
            b->set_first_name();
            b->last_name();
        }
};

Is this not correct?

You mean it prints "enter the id" and then after you enter an ID it doesn't continue? — Joseph Mansfield
– Joseph Mansfield, Commented Dec 21, 2013 at 13:57
All of the pointers in a are uninitialized when you initialize a2 with them. — Qaz
– Qaz, Commented Dec 21, 2013 at 13:58
@sftrabbit Yes , i did the cout and cin for the others (first name , last name ) but it didn't show up , and the program stop running — Rai Ou
– Rai Ou, Commented Dec 21, 2013 at 13:59

Joseph Mansfield · Accepted Answer · 2013-12-21 14:08:38Z

1

You allocate size amount of A*s, but you don't actually make those pointers point anywhere. ~~They're uninitialized.~~ Edit: now you're just setting them to NULL. You would need to allocate some A objects and assign their addresses to each of the elements of a. However, I see no good reason for you to be dynamically allocating the array of pointers - why don't you just declare a as A* a[10];? (or better yet, use a std::vector or std::array)

edited Dec 21, 2013 at 14:08

answered Dec 21, 2013 at 14:01

Joseph Mansfield

111k22 gold badges249 silver badges329 bronze badges

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

4 Comments

Rai Ou Over a year ago

I use the dynamically allocating because of the phone_number , i couldn't reach it without dynamically allocating !

juanchopanza Over a year ago

@RaiOu It looks more like you use dynamic allocation because you don't know how to use standard library containers.

Gabriel L. Over a year ago

Just a side remark : he never deallocate his A objects. That's a problem when allocating objects, it's easy to forget to deallocate them.

juanchopanza Over a year ago

@GabrielL. that would lead to undefined behaviour, because A has no virtual destructor :-)

Collectives™ on Stack Overflow

Initializing array of objects

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related