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STL Container Cleanup
Submitted by |
A lot of people use STL (Standard Template Library) template containers for
their collections. So does my friend. He has more than ten instantiated
templates of vectors, lists and other container templates.
The thing is that he stores pointers to base classes then makes some derive
instances and stores the base pointer into the collection. Then the same old
story ... polymorph...orph..
He new that when he cleared the containers with clear() method of the
container pointers are not touched. (beware if you use your the same pointer
in several different collection this can cause you trouble) So, he had to
write a boring cycle for every single collection to delete all pointers
residing there.
So was born our templatized "stlwipe" function which looks like this:
template<class T
void stlwipe(T &t)
{
//get the first iterator
T::iterator i=t.begin();
//iterate to the end and delete items (should be pointers)
for(; i!=t.end();++i) delete(*i);
//clear the collection (now full with dead pointers)
t.clear();
} |
The only thing the programmer does is calling the "stlwipe" function with
parameter the container itself... the template is implicitly instantiated
and your collection is successfully wiped (with proper virtual destructors
called)
An example:
vector<Base * vpBase;
vpBase.push_back(new Derived());
vpBase.push_back(new Derived2());
vpBase.push_back(new Derived3());
//wipe it out
stlwipe(vpBase); |
Simple isnt it?
To be honest here is what Bruce Eckel (Thinking in C++) wrote about this:
// Template function:
template <class T
void wipe(T* x) { delete x; }
//then you simply do
for_each(vpBase.begin(), vpBase.end(), wipe<Base); |
In this case you should know what is the type of the contained elements
while in our function you simply pass the container it self and it does it
for you.
:)
Kind regards,
Yordan (WarJo) Gyurchev
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