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# Q3PtrStack Class Reference
[Qt3Support module]

The Q3PtrStack class is a template class that provides a stack. More...

     #include <Q3PtrStack>

This class is part of the Qt 3 support library. It is provided to keep old source code working. We strongly advise against using it in new code. See Porting to Qt 4 for more information.

Inherits Q3PtrCollection.

- List of all members, including inherited members

### Public Functions

- Q3PtrStack ()
- Q3PtrStack ( const Q3PtrStack<type> & s )
- ~Q3PtrStack ()
- bool autoDelete () const
- virtual void clear ()
- virtual uint count () const
- type * current () const
- bool isEmpty () const
- type * pop ()
- void push ( const type * d )
- bool remove ()
- void setAutoDelete ( bool enable )
- type * top () const
- operator type * () const
- Q3PtrStack<type> & operator= ( const Q3PtrStack<type> & s )

- 4 public functions inherited from Q3PtrCollection

### Protected Functions

- virtual QDataStream & read ( QDataStream & s, Q3PtrCollection::Item & item )
- virtual QDataStream & write ( QDataStream & s, Q3PtrCollection::Item item ) const

- 2 protected functions inherited from Q3PtrCollection

## Detailed Description

The Q3PtrStack class is a template class that provides a stack.

Q3ValueStack is an STL-compatible alternative to this class.

Define a template instance Q3PtrStack<X> to create a stack that operates on pointers to X, (X*).

A stack is a last in, first out (LIFO) structure. Items are added to the top of the stack with push() and retrieved from the top with pop(). Use top() to get a reference to the top element without changing the stack.

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

For compatibility with the Q3PtrCollection classes current() and remove() are provided; they both operate on the top().

See also Q3PtrList and Q3PtrQueue.

## Member Function Documentation

### Q3PtrStack::Q3PtrStack ()

Creates an empty stack.

### Q3PtrStack::Q3PtrStack ( const Q3PtrStack<type> & s )

Creates a stack by making a shallow copy of another stack s.

### Q3PtrStack::~Q3PtrStack ()

Destroys the stack. All items will be deleted if autoDelete() is true.

### bool Q3PtrStack::autoDelete () const

The same as Q3PtrCollection::autoDelete(). Returns true if the auto-delete option is set. If the option is set, the stack auto-deletes its contents.

See also setAutoDelete().

### void Q3PtrStack::clear () `[virtual]`

Removes all items from the stack, deleting them if autoDelete() is true.

Reimplemented from Q3PtrCollection.

See also remove().

### uint Q3PtrStack::count () const `[virtual]`

Returns the number of items in the stack.

Reimplemented from Q3PtrCollection.

See also isEmpty().

### type * Q3PtrStack::current () const

Returns a pointer to the top item on the stack (most recently pushed). The stack is not changed. Returns 0 if the stack is empty.

### bool Q3PtrStack::isEmpty () const

Returns true if the stack contains no elements; otherwise returns false.

### type * Q3PtrStack::pop ()

Removes the top item from the stack and returns it. The stack must not be empty.

### void Q3PtrStack::push ( const type * d )

Adds an element d to the top of the stack. Last in, first out.

### QDataStream & Q3PtrStack::read ( QDataStream & s, Q3PtrCollection::Item & item ) `[virtual protected]`

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

The default implementation sets item to 0.

See also write().

### bool Q3PtrStack::remove ()

Removes the top item from the stack and deletes it if autoDelete() is true. Returns true if there was an item to pop; otherwise returns false.

See also clear().

### void Q3PtrStack::setAutoDelete ( bool enable )

Defines whether this stack auto-deletes its contents. The same as Q3PtrCollection::setAutoDelete(). If enable is true, auto-delete is turned on.

If auto-deleting is turned on, all the items in the stack are deleted when the stack itself is deleted. This is convenient if the stack has the only pointers to the items.

The default setting is false, for safety. If you turn it on, be careful about copying the stack, or you might find yourself with two stacks 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().

### type * Q3PtrStack::top () const

Returns a pointer to the top item on the stack (most recently pushed). The stack is not changed. Returns 0 if the stack is empty.

### QDataStream & Q3PtrStack::write ( QDataStream & s, Q3PtrCollection::Item item ) const `[virtual protected]`

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

The default implementation does nothing.

See also read().

### Q3PtrStack::operator type * () const

Returns a pointer to the top item on the stack (most recently pushed). The stack is not changed. Returns 0 if the stack is empty.

### Q3PtrStack<type> & Q3PtrStack::operator= ( const Q3PtrStack<type> & s )

Sets the contents of this stack by making a shallow copy of another stack s. Elements currently in this stack will be deleted if autoDelete() is true.