如何在指针数组中插入对象

Question

I have an array of pointers:

Hotel *hotels[size];
  for (int i = 0; i < size; ++i)
    hotels[i] = new Hotel();

And I want to insert an object in this array after some object with name I know:

cin >> tmp_name;
for (int i = 0; i < size; i++) {
  if (hotels[i]->get_name() == tmp_name) {
    hotels[size] = new Hotel();
    size += 1;
    Hotel *tmp_hotel;
    tmp_hotel = hotels[i+1];
    hotels[i+1]->fillHotel();
    for (i = i + 2; i < size; i++) {
      hotels[i] = tmp_hotel;
      tmp_hotel = hotels[i+1];
    }
    break;
  }
}

What I do wrong?

UPD: My solution:

cin >> tmp_name;
for (int i = 0, j = 0; i < size; i++, j++) {
    new_hotels[j] = hotels[i];
    if (hotels[i]->get_name() == tmp_name) {
        new_hotels[j+1]->fillHotel();
        ++j;
        system("clear");
    }
}

hotels[size] = new Hotel();
++size;
for (int i = 0; i < size; i++) {
    hotels[i] = new_hotels[i];
}

Answer 1

I can see different errors in your code.

---

For example:

Hotel *hotels[size];

size should be a constant expression and something let me think this is not the case. VLA are not part of the C++ standard. In short you cannot allocate dynamic memory on the stack. The proper initialization should be:

Hotel* hotels = new Hotel*[size];

---

The line in the loop:

hotels[size] = new Hotel();

you're actually accessing out of bounds of your array: size index is some memory is not included in your array and this will produce an undefined behaviour .

---

Another strange line is the following:

size += 1;

Despite the fact that confirms size is not a constant, you cannot increase your size of vector simply changing that variable. You're actually just changing a variable size , but the allocated memory for your array will be the same.

---

How resolve?

In order in increase (or change) the size of an array, the solution is almost always to create a new array, copy the old one. In your case that solution is pretty reasonable because you should copy just pointers and not entire objects.

There are a lots of question on SO where this topic is, for example here .

Despite of that, I strongly suggest you to use the most practical alternative, that is to use a real C++ code .

The most efficient class is std::vector which is a C++ way to handle dynamic array.

Finally, you should also consider the std::unique_ptr<T> class to handle dynamic memory and pointers.

The final solution will be a class:

std::vector<std::unique_ptr<Hotel>> hotels;