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# QPtrQueue Class Reference

The QPtrQueue class is a template class that provides a queue. More...

`#include <qptrqueue.h>`

List of all member functions.

## Public Members

- QPtrQueue ()
- QPtrQueue ( const QPtrQueue<type> & queue )
- ~QPtrQueue ()
- QPtrQueue<type> & operator= ( const QPtrQueue<type> & queue )
- bool autoDelete () const
- void setAutoDelete ( bool enable )
- uint count () const
- bool isEmpty () const
- void enqueue ( const type * d )
- type * dequeue ()
- bool remove ()
- void clear ()
- type * head () const
- operator type * () const
- type * current () const

## Protected Members

- virtual QDataStream & read ( QDataStream & s, QPtrCollection::Item & item )
- virtual QDataStream & write ( QDataStream & s, QPtrCollection::Item item ) const

## Detailed Description

The QPtrQueue class is a template class that provides a queue.

QValueVector can be used as an STL-compatible alternative to this class.

A template instance QPtrQueue<X> is a queue that operates on pointers to X (X*).

A queue is a first in, first out structure. Items are added to the tail of the queue with enqueue() and retrieved from the head with dequeue(). You can peek at the head item without dequeing it using head().

You can control the queue's deletion policy with setAutoDelete().

For compatibility with the QPtrCollection classes, current() and remove() are provided; both operate on the head().

See also QPtrList, QPtrStack, Collection Classes, and Non-GUI Classes.

## Member Function Documentation

### QPtrQueue::QPtrQueue ()

Creates an empty queue with autoDelete() set to FALSE.

### QPtrQueue::QPtrQueue ( const QPtrQueue<type> & queue )

Creates a queue from queue.

Only the pointers are copied; the items are not. The autoDelete() flag is set to FALSE.

### QPtrQueue::~QPtrQueue ()

Destroys the queue. Items in the queue are deleted if autoDelete() is TRUE.

### bool QPtrQueue::autoDelete () const

Returns the setting of the auto-delete option. The default is FALSE.

See also setAutoDelete().

### void QPtrQueue::clear ()

Removes all items from the queue, and deletes them if autoDelete() is TRUE.

See also remove().

### uint QPtrQueue::count () const

Returns the number of items in the queue.

See also isEmpty().

### type * QPtrQueue::current () const

Returns a pointer to the head item in the queue. The queue is not changed. Returns 0 if the queue is empty.

See also dequeue() and isEmpty().

### type * QPtrQueue::dequeue ()

Takes the head item from the queue and returns a pointer to it. Returns 0 if the queue is empty.

See also enqueue() and count().

### void QPtrQueue::enqueue ( const type * d )

Adds item d to the tail of the queue.

See also count() and dequeue().

### type * QPtrQueue::head () const

Returns a pointer to the head item in the queue. The queue is not changed. Returns 0 if the queue is empty.

See also dequeue() and isEmpty().

### bool QPtrQueue::isEmpty () const

Returns TRUE if the queue is empty; otherwise returns FALSE.

See also count(), dequeue(), and head().

### QPtrQueue::operator type * () const

Returns a pointer to the head item in the queue. The queue is not changed. Returns 0 if the queue is empty.

See also dequeue() and isEmpty().

### QPtrQueue<type> & QPtrQueue::operator= ( const QPtrQueue<type> & queue )

Assigns queue to this queue and returns a reference to this queue.

This queue is first cleared and then each item in queue is enqueued to this queue. Only the pointers are copied.

Warning: The autoDelete() flag is not modified. If it it TRUE for both queue and this queue, deleting the two lists will cause double-deletion of the items.

### QDataStream & QPtrQueue::read ( QDataStream & s, QPtrCollection::Item & item )`[virtual protected]`

Reads a queue item, item, from the stream s and returns a reference to the stream.

The default implementation sets item to 0.

See also write().

### bool QPtrQueue::remove ()

Removes the head item from the queue, and returns TRUE if there was an item, i.e. the queue wasn't empty; otherwise returns FALSE.

The item is deleted if autoDelete() is TRUE.

See also head(), isEmpty(), and dequeue().

### void QPtrQueue::setAutoDelete ( bool enable )

Sets the queue to auto-delete its contents if enable is TRUE and not to delete them if enable is FALSE.

If auto-deleting is turned on, all the items in a queue are deleted when the queue itself is deleted. This can be quite convenient if the queue has the only pointer to the items.

The default setting is FALSE, for safety. If you turn it on, be careful about copying the queue: you might find yourself with two queues deleting the same items.

See also autoDelete().

### QDataStream & QPtrQueue::write ( QDataStream & s, QPtrCollection::Item item ) const`[virtual protected]`

Writes a queue item, item, to the stream s and returns a reference to the stream.

The default implementation does nothing.

See also read().

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