Re: Problem in deleting entries from Hash_set

ZikO <>
Sat, 07 Mar 2009 03:58:15 +0000
Prafulla T wrote:
 > for (hash_set<UserType*>::iterator hashIt = hashSet.begin();
 > hashIt != hashSet.end(); hashIt++)
 > {
 > UserType *pUserType = *hashIt;
 > hashIt++;
 > delete pUserType;
 > pUserType = NULL;
 > }

OK. First of all you cannot use hash_set.begin(). hash_set<> is the type
not instantiated object! If this worked, that code below would also work !!!
template <class T>
struct A {
    void begin() {}
int main() {
    //! A.f(); // very baaaad :P
    A<int> a;
    a.f(); // correct

So you have to have an instantiated object of hash_set<UserType*>
somewhere ... let's say it's:

hash_set<UserType*> hsutp;

Before I write the code a few things to be said.
* you increments iterator two times, in for definition and in code
inside the loop !!!
* you are trying to delete object pointed by pUserType, which has not
been created dynamically by operator new !!!
* you compare pointers of two different objects, UserType with container
hash_set !!!

Now having said that all, if I understand you, your code should look
like below (roughly):

// ...
hash_set<UserType*> hsutp; // it can be any name used by you
                            // I assume u have done something on
                            // this object !!!
// ...
for (hash_set<UserType*>::iterator hashIt = hsutp.begin();
           hashIt != hsutp.end(); ++hashIt) {
   delete *hashIt;
   *hashIt = 0;


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