Thread: delete a pointer held by a list container

example

Code:

aClass * aObject = new aClass;

std::list<aClass> aClassList;

aClassList.push_back(aObject);

//do lots of stuff passing the list back and forth among functions

aClassList.erase();

the problem is that aObject doesn't get deleted.

How do I solve this?

Thanks for any help.

Hi,

Your list does not contain objects--it contains pointers to objects. When you use erase(), the pointers are removed from the list. Removing pointers from a list does nothing to the original objects.

If you had an array of pointers to objects, how would you delete the objects those pointers point to? Or, more simply: if you have a pointer to one object, how would you delete the object?

I have tried the following but it did not work.

Code:

std::list<aClass>::iterator iaClass = aClassList.begin();

while(iaClass != aClassList.end())
{
     delete &iaClass;
     iaClass++;
}

I guess i'm not sure how to access the object pointed to by iaClass.

Originally Posted by alphaoide

should be this

Code:

delete *iaClass;

I get the following error.

C:\unzipped\binary\main.cpp(183) : error C2440: 'delete' : cannot convert from 'class aClass' to ''

Just in random attempts, I have tried many combinations.

Originally Posted by nineofhearts

I have tried the following but it did not work.

Code:

std::list<aClass>::iterator iaClass = aClassList.begin();

while(iaClass != aClassList.end())
{
     delete &iaClass;
     iaClass++;
}

The problem with this code is that your list doesn't hold pointers.
If it would contain pointers use

Code:

     delete *iaClass;

Originally Posted by alphaoide

Hmm, maybe you have to cast

Code:

delete reinterpret_cast<aClass *>(*iaClass);

No. Just put pointers into the list ( otherwise there is no need to delete anything )

Code:

aClass * aObject = new aClass;
std::list<aClass*> aClassPtrList;
aClassList.push_back(aObject);
for ( std::list<aObject*>::iterator i= aClassPtrList.begin(); i != aClassPtrList.end(); ++i )
   delete *i;
aClassPtrList.erase();

Originally Posted by ZuK

Code:

aClass * aObject = new aClass;
std::list<aClass*> aClassPtrList;
aClassList.push_back(aObject);
for ( std::list<aObject*>::iterator i= aClassPtrList.begin(); i != aClassPtrList.end(); ++i )
   delete *i;
aClassPtrList.erase();

Zuk, this solved the problem. Thank you sooooo much.