DestructElements & CMap
Ron Jacobs -- Ron.Jacobs@centurasoft.com
Thursday, April 03, 1997
Environment: Win95 VC 2.2
I am using a CMap to store a collection of objects in my application.
My problem is that my override of the function DestructElements never
gets called.
// Global helpers for managing a collection of items.
inline void ConstructElements(CDKItem* pElements, int nCount)
{
ASSERT(nCount == 0 ||
AfxIsValidAddress(pElements, nCount * sizeof(CDKItem)));
for ( int i = 0; i < nCount; i++, pElements++ )
{
// call CDKItem default constructor directly
pElements->CDKItem::CDKItem();
}
}
inline void DestructElements(CDKItem* pElements, int nCount)
{
ASSERT(nCount == 0 ||
AfxIsValidAddress(pElements, nCount * sizeof(CDKItem)));
for ( int i = 0; i < nCount; i++, pElements++ )
{
// call CDKItem default constructor directly
pElements->CDKItem::~CDKItem();
delete pElements;
}
}
inline UINT HashKey(CString sKey)
{
LPSTR key = sKey.GetBuffer(0);
UINT nHash = 0;
while (*key)
nHash = (nHash<<5) + nHash + *key++;
return nHash;
}
typedef CMap
CMapStringToCDKItem;
Any clues as to why this doesn't get called?
Hugh Robinson -- hugh@ssihou.ssii.com
Thursday, April 03, 1997
[Mini-digest: 3 responses]
I would suggest that the functions should be declared with an extra level
of indirection, i.e.
inline void ConstructElements(CDKItem** pElements, int nCount);
inline void DestructElements(CDKItem** pElements, int nCount);
It may also
----------
From: owner-mfc-l
Sent: Thursday, April 03, 1997 10:34 AM
To: mfc-l
Subject: DestructElements & CMap
Environment: Win95 VC 2.2
I am using a CMap to store a collection of objects in my
application.
My problem is that my override of the function DestructElements
never
gets called.
// Global helpers for managing a collection of items.
inline void ConstructElements(CDKItem* pElements, int nCount)
{
ASSERT(nCount == 0 ||
AfxIsValidAddress(pElements, nCount * sizeof(CDKItem)));
for ( int i = 0; i < nCount; i++, pElements++ )
{
// call CDKItem default constructor directly
pElements->CDKItem::CDKItem();
}
}
inline void DestructElements(CDKItem* pElements, int nCount)
{
ASSERT(nCount == 0 ||
AfxIsValidAddress(pElements, nCount * sizeof(CDKItem)));
for ( int i = 0; i < nCount; i++, pElements++ )
{
// call CDKItem default constructor directly
pElements->CDKItem::~CDKItem();
delete pElements;
}
}
inline UINT HashKey(CString sKey)
{
LPSTR key = sKey.GetBuffer(0);
UINT nHash = 0;
while (*key)
nHash = (nHash<<5) + nHash + *key++;
return nHash;
}
typedef CMap
CMapStringToCDKItem;
Any clues as to why this doesn't get called?
-----From: =?iso-8859-1?Q?Klaus_G=FCtter?=
Ron,
your class CMapStringToCDKItem contains _pointers_, not objects. As all
MFC's collection classes containing pointers, CMap is not responsible
for freeing the object. This is why your DestructElements is not called.
The collection helper functions are only needed when the collection
contains objects, e.g.
CMap.
- Klaus
>----------
>Von: Ron Jacobs[SMTP:Ron.Jacobs@centurasoft.com]
>Gesendet: Donnerstag, 3. April 1997 20:34
>An: mfc-l@netcom.com
>Betreff: DestructElements & CMap
>
> Environment: Win95 VC 2.2
>
> I am using a CMap to store a collection of objects in my application.
> My problem is that my override of the function DestructElements never
> gets called.
>
> // Global helpers for managing a collection of items.
> inline void ConstructElements(CDKItem* pElements, int nCount)
> {
> ASSERT(nCount == 0 ||
> AfxIsValidAddress(pElements, nCount * sizeof(CDKItem)));
>
> for ( int i = 0; i < nCount; i++, pElements++ )
> {
> // call CDKItem default constructor directly
> pElements->CDKItem::CDKItem();
> }
>
> }
>
> inline void DestructElements(CDKItem* pElements, int nCount)
> {
> ASSERT(nCount == 0 ||
> AfxIsValidAddress(pElements, nCount * sizeof(CDKItem)));
>
> for ( int i = 0; i < nCount; i++, pElements++ )
> {
> // call CDKItem default constructor directly
> pElements->CDKItem::~CDKItem();
> delete pElements;
> }
> }
>
> inline UINT HashKey(CString sKey)
> {
> LPSTR key = sKey.GetBuffer(0);
> UINT nHash = 0;
> while (*key)
> nHash = (nHash<<5) + nHash + *key++;
> return nHash;
> }
>
> typedef CMap
> CMapStringToCDKItem;
>
>
> Any clues as to why this doesn't get called?
>
>
>
-----From: Stuart Downing
>----------
From: Ron Jacobs[SMTP:Ron.Jacobs@centurasoft.com]
>Subject: DestructElements & CMap
>
> Environment: Win95 VC 2.2
I don't have access to VC 2.2, so my answers assume that the collection
classes haven't changed substantially since then.
>
> I am using a CMap to store a collection of objects in my application.
> My problem is that my override of the function DestructElements never
> gets called.
>
> inline void DestructElements(CDKItem* pElements, int nCount)
> {
> ASSERT(nCount == 0 ||
> AfxIsValidAddress(pElements, nCount * sizeof(CDKItem)));
>
> for ( int i = 0; i < nCount; i++, pElements++ )
> {
> // call CDKItem default constructor directly
> pElements->CDKItem::~CDKItem();
> delete pElements;
Trouble: Your DestructElements should call the destructor function, but
should NOT call delete. You are destructing an object in place, but
NOT freeing the associated memory.
> }
> }
>
> typedef CMap
> CMapStringToCDKItem;
Your CMap is mapping CStrings to *pointers* to CDKItems. The map
doesn't contain CDKItems objects themselves, just the pointers.
This collection does not own the CDKItems, and will not delete them
for you.
-----
Stuart Downing
sdowning@fame.com
FAME Information Services, Inc.
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