The QPtrCollection class is the base class of most pointer-based Qt collections.
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Detailed Description
The QPtrCollection class is the base class of most pointer-based Qt collections.
The QPtrCollection class is an abstract base class for the Qt
collection classes QDict, QPtrList,
etc. Qt also includes value based collections, e.g. QValueList,
QMap, etc.
A QPtrCollection only knows about the number of objects in the
collection and the deletion strategy (see setAutoDelete()).
A collection is implemented using the Item (generic collection
item) type, which is a void*. The template classes that create
the real collections cast the Item to the required type.
See also Collection Classes and Non-GUI Classes.
Member Type Documentation
QPtrCollection::Item
This type is the generic "item" in a QPtrCollection.
Member Function Documentation
QPtrCollection::QPtrCollection () [protected]
Constructs a collection. The constructor is protected because
QPtrCollection is an abstract class.
QPtrCollection::QPtrCollection ( const QPtrCollection & source ) [protected]
Constructs a copy of source with autoDelete() set to FALSE. The
constructor is protected because QPtrCollection is an abstract
class.
Note that if source has autoDelete turned on, copying it will
risk memory leaks, reading freed memory, or both.
QPtrCollection::~QPtrCollection () [virtual protected]
Destroys the collection. The destructor is protected because
QPtrCollection is an abstract class.
bool QPtrCollection::autoDelete () const
Returns the setting of the auto-delete option. The default is FALSE.
See also setAutoDelete().
void QPtrCollection::clear () [pure virtual]
Removes all objects from the collection. The objects will be
deleted if auto-delete has been enabled.
See also setAutoDelete().
Reimplemented in QAsciiDict, QCache, QDict, QIntDict, QPtrList, QPtrDict and QPtrVector.
uint QPtrCollection::count () const [pure virtual]
Returns the number of objects in the collection.
Reimplemented in QAsciiDict, QCache, QDict, QIntDict, QPtrList, QPtrDict and QPtrVector.
void QPtrCollection::deleteItem ( Item d ) [pure virtual protected]
Reimplement this function if you want to be able to delete items.
Deletes an item that is about to be removed from the collection.
This function has to reimplemented in the collection template
classes, and should only delete item d if auto-delete has
been enabled.
Warning: If you reimplement this function you must also
reimplement the destructor and call the virtual function clear()
from your destructor. This is due to the way virtual functions and
destructors work in C++: Virtual functions in derived classes
cannot be called from a destructor. If you do not do this, your
deleteItem() function will not be called when the container is
destroyed.
See also newItem() and setAutoDelete().
Item QPtrCollection::newItem ( Item d ) [virtual protected]
Virtual function that creates a copy of an object that is about to
be inserted into the collection.
The default implementation returns the d pointer, i.e. no copy
is made.
This function is seldom reimplemented in the collection template
classes. It is not common practice to make a copy of something
that is being inserted.
See also deleteItem().
void QPtrCollection::setAutoDelete ( bool enable )
Sets the collection to auto-delete its contents if enable is
TRUE and to never delete them if enable is FALSE.
If auto-deleting is turned on, all the items in a collection are
deleted when the collection itself is deleted. This is convenient
if the collection has the only pointer to the items.
The default setting is FALSE, for safety. If you turn it on, be
careful about copying the collection - you might find yourself
with two collections deleting the same items.
Note that the auto-delete setting may also affect other functions
in subclasses. For example, a subclass that has a remove()
function will remove the item from its data structure, and if
auto-delete is enabled, will also delete the item.
See also autoDelete().
Examples: grapher/grapher.cpp, scribble/scribble.cpp and table/bigtable/main.cpp.
This file is part of the Qt toolkit.
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