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deleting all elements in a STL container of pointers

Can anyone see anything wrong with the following code?

(CONTAINER can be list, vector, set, ...)

template <class T> void Destroy(T * p) { delete p; }

void CleanUp(std::CO NTAINER<Contain erType *> & Container)
{
std::foreach(Co ntainer.begin() , Container.end() ,
Destroy<Contain erType>);
Container.clear ();
}

Dec 17 '05 #1
5 2761
ed**********@gm ail.com wrote:
Can anyone see anything wrong with the following code?

(CONTAINER can be list, vector, set, ...)

template <class T> void Destroy(T * p) { delete p; }

void CleanUp(std::CO NTAINER<Contain erType *> & Container)
{
std::foreach(Co ntainer.begin() , Container.end() ,
Destroy<Contain erType>);
Container.clear ();
}

Sorry for my english,

In your Cleanup function, where do you define the formal parameter of
your template ?

To erase a item collection, you can use a functor.
Look my struct template 'Destroy', with this declaration (and definition).

template <typename T> struct Destroy {
void operator () (T pointer) {
std::cout << "Destroy of this pointer" << std::endl;
delete pointer;
pointer = 0;
}
};

Here, you must to define the type of your container :
The type is detected by the instantiation of your template.

template <typename Container> void CleanUp (Container & pContainer) {
std::for_each (
pContainer.begi n (),
pContainer.end (),
Destroy<typenam e Container::valu e_type> ());
}

in your main function :

int main (int argc, char **argv) {
std::vector <std::string *> vect;
vect.push_back (new std::string ("Stephane") );
CleanUp (vect);
}

Best regards,

Stephane
Dec 17 '05 #2
ed**********@gm ail.com wrote:
Can anyone see anything wrong with the following code?

(CONTAINER can be list, vector, set, ...)

template <class T> void Destroy(T * p) { delete p; }

void CleanUp(std::CO NTAINER<Contain erType *> & Container)
{
std::foreach(Co ntainer.begin() , Container.end() ,
Destroy<Contain erType>);
Container.clear ();
}

About this subject, I have good advice for you.

Buy the book : "C++ Templates : The Complete Guide"
Product Details

* Hardcover: 552 pages
* Publisher: Addison-Wesley Professional; 1st edition (November 12,
2002)
* Language: English
* ISBN: 0201734842
* Product Dimensions: 9.5 x 7.5 x 1.2 inches
Dec 17 '05 #3
I'd also add Scott Meyers' "Effective STL" and Item 7.

Cheers
--
Mateusz Loskot
http://mateusz.loskot.net

Dec 17 '05 #4

ed**********@gm ail.com wrote:
Can anyone see anything wrong with the following code?

(CONTAINER can be list, vector, set, ...)

template <class T> void Destroy(T * p) { delete p; }

void CleanUp(std::CO NTAINER<Contain erType *> & Container)
{
std::foreach(Co ntainer.begin() , Container.end() ,
Destroy<Contain erType>);
Container.clear ();
}


I recommend you use smart pointers in your container instead of raw
pointers.
If you use smart pointers, then you don't have to worry about
explicitly deleting the pointers, because the smart pointer will do
that for you.
You can use the boost::shared_p tr or clone smart pointers like copy_ptr
and cow_ptr.

http://www.boost.org/libs/smart_ptr/shared_ptr.htm

http://code.axter.com/copy_ptr.h
http://code.axter.com/cow_ptr.h

Example usage:
std::vector<boo st::shared_ptr< foo> > vFoo;

std::vector<cop y_ptr<foo> > vFoo;

Dec 18 '05 #5

ed**********@gm ail.com wrote:
Can anyone see anything wrong with the following code?

(CONTAINER can be list, vector, set, ...)

template <class T> void Destroy(T * p) { delete p; }

void CleanUp(std::CO NTAINER<Contain erType *> & Container)
{
std::foreach(Co ntainer.begin() , Container.end() ,
Destroy<Contain erType>);
Container.clear ();
}


The problem is that there can be a problem using Destroy<Contain erType>
as a template function. Although you can use a function in this
situation, it doesn't work with template functions.

So you should use a functor as other posters have suggested.

Dec 19 '05 #6

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