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.

What you store is just a list of *pointers* to objects, so when you "erase," the pointers are deleted but the objects still there.

You need to loop thru the list and "delete" each object, then you can "erase" the list.

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.

should be this

Code:

---

delete *iaClass;

---

Quote:

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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.

Quote:

---

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;

---

Hmm, maybe you have to cast

Code:

---

delete reinterpret_cast<aClass *>(*iaClass);

---

Quote:

---

Originally Posted by alphaoide

Hmm, maybe you have to cast

Code:

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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();

---

Quote:

---

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

---

iaClass is a horrible non-descriptive name as is aObject since you do this:

aClass * aObject = new aClass;

aObject is not an object--it is a pointer to an object. I think if you used some descriptive variable names, you might get things straightened out.

An interator acts like a pointer to the things in your list. So, iaClass acts like a pointer to things in your list. To get the things in your list, you need to dereference iaClass.

Code:

---

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.

---

Post all the code that produces that error.

Quote:

---

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();

---

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