Re: Deleting elements of vectors that contain pointers to other objects

From:
red floyd <redfloyd@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 19 Mar 2009 09:46:53 -0700 (PDT)
Message-ID:
<d281aadd-a0bb-4399-8607-2c5286dc6e26@c36g2000yqn.googlegroups.com>
On Mar 19, 9:39 am, dwightarmyofchampi...@hotmail.com wrote:

How exactly do I delete elements of a vector in the destructor?
Suppose my vector in my class definition looks like this:

std::vector<ABC*> vec;

which means I am declaring a vector whose elements will contain
pointer to ABC objects.

...and in my constructor I have:

vec.clear(); // make sure vector is empty before populating it

for (int i = 0; i < 5; i++)
{
  ABC* abcobject1 = new ABC(i);
  vec.push_back(abcobject1);

}

When I go to my destructor, do I just need to pop_back() the vector
elements...

for (int i = 0; i < 5; i++)
{
  vec.pop_back();

}

...or do I delete each ABC object and then pop_back its corresponding
vector pointer...

for (int i = 0; i < 5; i++)
{
   delete vec[i]; vec[i] = 0; // or is it (*vec[i])???
   vec.pop_back();

}

...or do I do something else? Isn't there a delete[] statement for
this sort of thing?


This is a question of ownership. That's why you need to document who
owns what. If the vector is intended to own the pointers, you
probably shouldn't store raw pointer, but instead use your favorite
smart pointer.

If you're using raw pointers, you need to delete the elements
individually.

for (std::vector<ABC*>::iterator it = vec.begin();
     it != vec.end();
     ++it)
{
    delete *it;
    *it = 0; // probably optional
}

If you're using smart pointers, where smart_ptr_t<> is your favorite
smart pointer:

std::vector<smart_ptr_t<ABC> > vec;
Then, when vec is deleted, it invokes the smart_ptr_t<> destructor on
every element,
and the smart_ptr_t<> destructor handles the memory management.

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