Delete any container using templates

Question

I have a lot of code where I am deleting vector containers that have pointers in them, that is, I have to delete all the pointers first and then clear the container. Every time I would iterate through and delete the pointers manually (I am aware of stl::algorithms for_each). To circumvent all that code, I created a template for deleting all vector containers that have a pointer. So far so good.

Now I have several more container types including maps, concurrent containers etc. all with the same functionality in the end as far as deletion goes. The DeleteContainer(std::vector<T*>& VecIn) function that I have can only work on vectors as mentioned above. Is there any way to make it generic enough to work on all containers?

EDIT: Thanks for all the answers, I wish I could select more than one. To anybody who stumbles onto this question, read all the answers and not just the selected one as they all provide great info.

Answer 1

You already have a valid answer, but just to provide an alternative, I believe you should consider using Boost Pointer Container and let it handle memory management :

This library therefore provides standard-like containers that are for storing heap-allocated or cloned objects (or in case of a map, the mapped object must be a heap-allocated or cloned object). For each of the standard containers there is a pointer container equivalent that takes ownership of the objects in an exception safe manner.

Answer 2

You could use boost pointer containers.
They hold maintain and delete pointers correctly.

http://www.boost.org/doc/libs/1_38_0/libs/ptr_container/doc/reference.html

{
    boost::ptr_vector<int>   data;

    data.push_back(new int(2));
    data.push_back(new int(2));
    data.push_back(new int(2));
}
// container deleted and all pointers correctly destroyed.

Answer 3

I'll second many people and avise using shared_ptr or boost pointer containers. However, you can write

template <typename Iter>  
void delete_pointers(Iter begin, Iter end)
{
    for (; begin != end; ++begin) delete *begin;
}

Usage:

std::vector<Foo*> v;

// Initialize Foo objects

delete_pointers(v.rbegin(), v.rend());

I use rbegin and rend instead of begin and end because sometimes, people want objects to be deleted in the reverse order they were created.

You can also do

void destroyFoo(Foo* x) { delete x; }

std::for_each(v.rbegin(), v.rend(), &destroyFoo);

or use C++0x lambdas.

Answer 4

You can just use boost::shared_ptr<T> insted of T* and there will not be reason of DeleteContainer. But If you don't want to do this, you can make something like this

template<class T>
void DeleteContainer(typename T::iterator begin, typename T::iterator end)
{
 for(;begin!=end;++begin)
  delete *begin;
}

then you can just call it for any stl container you want in this way:

std::some_container<int*> s;
DeleteContainer<std::some_container<int*> > (s.begin(), s.end());