The Q3PtrCollection class is the base class of most pointer-based Qt collections. 更多...
| 头： | #include <Q3PtrCollection> |
| 继承者： | Q3AsciiCache , Q3AsciiDict , Q3Cache , Q3Dict , Q3IntCache , Q3IntDict , Q3PtrDict , Q3PtrList , Q3PtrQueue , Q3PtrStack ，和 Q3PtrVector |
注意： 此类的所有函数 可重入 .
| typedef | Item |
| bool | autoDelete () const |
| virtual void | clear () = 0 |
| virtual uint | count () const = 0 |
| void | setAutoDelete (bool enable ) |
| Q3PtrCollection () | |
| Q3PtrCollection (const Q3PtrCollection & source ) | |
| virtual | ~Q3PtrCollection () |
| virtual void | deleteItem (Item d ) = 0 |
| virtual Item | newItem (Item d ) |
The Q3PtrCollection class is the base class of most pointer-based Qt collections.
The Q3PtrCollection class is an abstract base class for the Qt collection classes QDict, Q3PtrList ，等。
A Q3PtrCollection 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.
This type is the generic "item" in a Q3PtrCollection .
[protected]
Q3PtrCollection::
Q3PtrCollection
()
Constructs a collection. The constructor is protected because Q3PtrCollection is an abstract class.
[protected]
Q3PtrCollection::
Q3PtrCollection
(const
Q3PtrCollection
&
source
)
构造副本为 source with autoDelete () set to false. The constructor is protected because Q3PtrCollection is an abstract class.
注意，若 source has autoDelete turned on, copying it will risk memory leaks, reading freed memory, or both.
[virtual protected]
Q3PtrCollection::
~Q3PtrCollection
()
Destroys the collection. The destructor is protected because Q3PtrCollection is an abstract class.
Returns the setting of the auto-delete option. The default is false.
另请参阅 setAutoDelete ().
[pure virtual]
void
Q3PtrCollection::
clear
()
Removes all objects from the collection. The objects will be deleted if auto-delete has been enabled.
另请参阅 setAutoDelete ().
[pure virtual]
uint
Q3PtrCollection::
count
() const
Returns the number of objects in the collection.
[pure virtual protected]
void
Q3PtrCollection::
deleteItem
(
Item
d
)
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.
警告： 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.
另请参阅 newItem () 和 setAutoDelete ().
[virtual protected]
Item
Q3PtrCollection::
newItem
(
Item
d
)
Virtual function that creates a copy of an object that is about to be inserted into the collection.
默认实现返回 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.
另请参阅 deleteItem ().
Sets the collection to auto-delete its contents if enable is true and to never delete them if enable 为 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.
另请参阅 autoDelete ().