QPtrList(3qt)QPtrList(3qt)NAME
QPtrList - Template class that provides a list
SYNOPSIS
#include <qptrlist.h>
Inherits QPtrCollection.
Inherited by QObjectList, QSortedList, and QStrList.
Public Members
QPtrList ()
QPtrList ( const QPtrList<type> & list )
~QPtrList ()
QPtrList<type> & operator= ( const QPtrList<type> & list )
bool operator== ( const QPtrList<type> & list ) const
bool operator!= ( const QPtrList<type> & list ) const
virtual uint count () const
bool isEmpty () const
bool insert ( uint index, const type * item )
void inSort ( const type * item )
void prepend ( const type * item )
void append ( const type * item )
bool remove ( uint index )
bool remove ()
bool remove ( const type * item )
bool removeRef ( const type * item )
void removeNode ( QLNode * node )
bool removeFirst ()
bool removeLast ()
type * take ( uint index )
type * take ()
type * takeNode ( QLNode * node )
virtual void clear ()
void sort ()
int find ( const type * item )
int findNext ( const type * item )
int findRef ( const type * item )
int findNextRef ( const type * item )
uint contains ( const type * item ) const
uint containsRef ( const type * item ) const
bool replace ( uint index, const type * item )
type * at ( uint index )
int at () const
type * current () const
QLNode * currentNode () const
type * getFirst () const
type * getLast () const
type * first ()
type * last ()
type * next ()
type * prev ()
void toVector ( QGVector * vec ) const
Important Inherited Members
bool autoDelete () const
void setAutoDelete ( bool enable )
Protected Members
virtual int compareItems ( QPtrCollection::Item item1,
QPtrCollection::Item item2 )
virtual QDataStream & read ( QDataStream & s, QPtrCollection::Item &
item )
virtual QDataStream & write ( QDataStream & s, QPtrCollection::Item
item ) const
DESCRIPTION
The QPtrList class is a template class that provides a list.
QValueList is an STL-compatible alternative to this class.
Define a template instance QPtrList<X> to create a list that operates
on pointers to X (X*).
The list class is indexable and has a current index and a current item.
The first item corresponds to index position 0. The current index is -1
if the current item is 0.
Items are inserted with prepend(), insert() or append(). Items are
removed with remove(), removeRef(), removeFirst() and removeLast(). You
can search for an item using find(), findNext(), findRef() or
findNextRef(). The list can be sorted with sort(). You can count the
number of occurrences of an item with contains() or containsRef(). You
can get a pointer to the current item with current(), to an item at a
particular index position in the list with at() or to the first or last
item with getFirst() and getLast(). You can also iterate over the list
with first(), last(), next() and prev() (which all update current()).
The list's deletion property is set with setAutoDelete().
Example:
class Employee
{
public:
Employee() : sn( 0 ) { }
Employee( const QString& forename, const QString& surname, int salary )
: fn( forename ), sn( surname ), sal( salary )
{ }
void setSalary( int salary ) { sal = salary; }
QString forename() const { return fn; }
QString surname() const { return sn; }
int salary() const { return sal; }
private:
QString fn;
QString sn;
int sal;
};
QPtrList<Employee> list;
list.setAutoDelete( TRUE ); // the list owns the objects
list.append( new Employee("John", "Doe", 50000) );
list.append( new Employee("Jane", "Williams", 80000) );
list.append( new Employee("Tom", "Jones", 60000) );
Employee *employee;
for ( employee = list.first(); employee; employee = list.next() )
cout << employee->surname().latin1() << ", " <<
employee->forename().latin1() << " earns " <<
employee->salary() << endl;
cout << endl;
// very inefficient for big lists
for ( uint i = 0; i < list.count(); ++i )
if ( list.at(i) )
cout << list.at( i )->surname().latin1() << endl;
The output is
Doe, John earns 50000
Williams, Jane earns 80000
Jones, Tom earns 60000
Doe
Williams
Jones
QPtrList has several member functions for traversing the list, but
using a QPtrListIterator can be more practical. Multiple list iterators
may traverse the same list, independently of each other and of the
current list item.
In the example above we make the call setAutoDelete(TRUE). Enabling
auto-deletion tells the list to delete items that are removed. The
default is to not delete items when they are removed but this would
cause a memory leak in the example because there are no other
references to the list items.
When inserting an item into a list only the pointer is copied, not the
item itself, i.e. a shallow copy. It is possible to make the list copy
all of the item's data (deep copy) when an item is inserted. insert(),
inSort() and append() call the virtual function
QPtrCollection::newItem() for the item to be inserted. Inherit a list
and reimplement newItem() to have deep copies.
When removing an item from a list, the virtual function
QPtrCollection::deleteItem() is called. QPtrList's default
implementation is to delete the item if auto-deletion is enabled.
The virtual function compareItems() can be reimplemented to compare two
list items. This function is called from all list functions that need
to compare list items, for instance remove(const type*). If you only
want to deal with pointers, there are functions that compare pointers
instead, for instance removeRef(const type*). These functions are
somewhat faster than those that call compareItems().
List items are stored as void* in an internal QLNode, which also holds
pointers to the next and previous list items. The functions
currentNode(), removeNode(), and takeNode() operate directly on the
QLNode, but they should be used with care. The data component of the
node is available through QLNode::getData().
The QStrList class defined in qstrlist.h is a list of char*. It
reimplements newItem(), deleteItem() and compareItems(). (But see
QStringList for a list of Unicode QStrings.)
See also QPtrListIterator, Collection Classes, and Non-GUI Classes.
MEMBER FUNCTION DOCUMENTATIONQPtrList::QPtrList ()
Constructs an empty list.
QPtrList::QPtrList ( const QPtrList<;type> & list )
Constructs a copy of list.
Each item in list is appended to this list. Only the pointers are
copied (shallow copy).
QPtrList::~QPtrList ()
Removes all items from the list and destroys the list.
All list iterators that access this list will be reset.
See also setAutoDelete().
void QPtrList::append ( const type * item )
Inserts the item at the end of the list.
The inserted item becomes the current list item. This is equivalent to
insert( count(), item ).
item must not be 0.
See also insert(), current(), and prepend().
Examples:
type * QPtrList::at ( uint index )
Returns a pointer to the item at position index in the list, or 0 if
the index is out of range.
Sets the current list item to this item if index is valid. The valid
range is 0..(count() - 1) inclusive.
This function is very efficient. It starts scanning from the first
item, last item, or current item, whichever is closest to index.
See also current().
Examples:
int QPtrList::at () const
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Returns the index of the current list item. The returned value is -1 if
the current item is 0.
See also current().
bool QPtrCollection::autoDelete () const
Returns the setting of the auto-delete option. The default is FALSE.
See also setAutoDelete().
void QPtrList::clear () [virtual]
Removes all items from the list.
The removed items are deleted if auto-deletion is enabled.
All list iterators that access this list will be reset.
See also remove(), take(), and setAutoDelete().
Reimplemented from QPtrCollection.
int QPtrList::compareItems ( QPtrCollection::Item item1, QPtrCollection::Item
item2 ) [virtual protected]
This virtual function compares two list items.
Returns:
zero if item1 == item2
nonzero if item1 != item2
This function returns int rather than bool so that reimplementations
can return three values and use it to sort by:
0 if item1 == item2
> 0 (positive integer) if item1 > item2
< 0 (negative integer) if item1 < item2
inSort() requires that compareItems() is implemented as described here.
This function should not modify the list because some const functions
call compareItems().
The default implementation compares the pointers.
uint QPtrList::contains ( const type * item ) const
Returns the number of occurrences of item in the list.
The compareItems() function is called when looking for the item in the
list. If compareItems() is not reimplemented, it is more efficient to
call containsRef().
This function does not affect the current list item.
See also containsRef() and compareItems().
uint QPtrList::containsRef ( const type * item ) const
Returns the number of occurrences of item in the list.
Calling this function is much faster than contains() because contains()
compares item with each list item using compareItems(), whereas his
function only compares the pointers.
This function does not affect the current list item.
See also contains().
uint QPtrList::count () const [virtual]
Returns the number of items in the list.
See also isEmpty().
Examples:
Reimplemented from QPtrCollection.
type * QPtrList::current () const
Returns a pointer to the current list item. The current item may be 0
(implies that the current index is -1).
See also at().
QLNode * QPtrList::currentNode () const
Returns a pointer to the current list node.
The node can be kept and removed later using removeNode(). The
advantage is that the item can be removed directly without searching
the list.
Warning: Do not call this function unless you are an expert.
See also removeNode(), takeNode(), and current().
int QPtrList::find ( const type * item )
Finds the first occurrence of item in the list.
If the item is found, the list sets the current item to point to the
found item and returns the index of this item. If the item is not
found, the list sets the current item to 0, the current index to -1,
and returns -1.
The compareItems() function is called when searching for the item in
the list. If compareItems() is not reimplemented, it is more efficient
to call findRef().
See also findNext(), findRef(), compareItems(), and current().
int QPtrList::findNext ( const type * item )
Finds the next occurrence of item in the list, starting from the
current list item.
If the item is found, the list sets the current item to point to the
found item and returns the index of this item. If the item is not
found, the list sets the current item to 0, the current index to -1,
and returns -1.
The compareItems() function is called when searching for the item in
the list. If compareItems() is not reimplemented, it is more efficient
to call findNextRef().
See also find(), findNextRef(), compareItems(), and current().
int QPtrList::findNextRef ( const type * item )
Finds the next occurrence of item in the list, starting from the
current list item.
If the item is found, the list sets the current item to point to the
found item and returns the index of this item. If the item is not
found, the list sets the current item to 0, the current index to -1,
and returns -1.
Calling this function is much faster than findNext() because findNext()
compares item with each list item using compareItems(), whereas this
function only compares the pointers.
See also findRef(), findNext(), and current().
int QPtrList::findRef ( const type * item )
Finds the first occurrence of item in the list.
If the item is found, the list sets the current item to point to the
found item and returns the index of this item. If the item is not
found, the list sets the current item to 0, the current index to -1,
and returns -1.
Calling this function is much faster than find() because find()
compares item with each list item using compareItems(), whereas this
function only compares the pointers.
See also findNextRef(), find(), and current().
type * QPtrList::first ()
Returns a pointer to the first item in the list and makes this the
current list item; returns 0 if the list is empty.
See also getFirst(), last(), next(), prev(), and current().
Examples:
type * QPtrList::getFirst () const
Returns a pointer to the first item in the list, or 0 if the list is
empty.
This function does not affect the current list item.
See also first() and getLast().
type * QPtrList::getLast () const
Returns a pointer to the last item in the list, or 0 if the list is
empty.
This function does not affect the current list item.
See also last() and getFirst().
void QPtrList::inSort ( const type * item )
Inserts the item at its sorted position in the list.
The sort order depends on the virtual compareItems() function. All
items must be inserted with inSort() to maintain the sorting order.
The inserted item becomes the current list item.
item must not be 0.
Warning: Using inSort() is slow. An alternative, especially if you have
lots of items, is to simply append() or insert() them and then use
sort(). inSort() takes up to O(n) compares. That means inserting n
items in your list will need O(n^2) compares whereas sort() only needs
O(n*log n) for the same task. So use inSort() only if you already have
a presorted list and want to insert just a few additional items.
See also insert(), compareItems(), current(), and sort().
bool QPtrList::insert ( uint index, const type * item )
Inserts the item at position index in the list.
Returns TRUE if successful, i.e. if index is in range; otherwise
returns FALSE. The valid range is 0 to count() (inclusively). The item
is appended if index == count().
The inserted item becomes the current list item.
item must not be 0.
See also append(), current(), and replace().
bool QPtrList::isEmpty () const
Returns TRUE if the list is empty; otherwise returns FALSE.
See also count().
type * QPtrList::last ()
Returns a pointer to the last item in the list and makes this the
current list item; returns 0 if the list is empty.
See also getLast(), first(), next(), prev(), and current().
type * QPtrList::next ()
Returns a pointer to the item succeeding the current item. Returns 0 if
the current item is 0 or equal to the last item.
Makes the succeeding item current. If the current item before this
function call was the last item, the current item will be set to 0. If
the current item was 0, this function does nothing.
See also first(), last(), prev(), and current().
Examples:
bool QPtrList::operator!= ( const QPtrList<type> & list ) const
Compares this list with list. Returns TRUE if the lists contain
different data; otherwise returns FALSE.
QPtrList<;type> & QPtrList::operator= ( const QPtrList<type> & list )
Assigns list to this list and returns a reference to this list.
This list is first cleared and then each item in list is appended to
this list. Only the pointers are copied (shallow copy) unless newItem()
has been reimplemented.
bool QPtrList::operator== ( const QPtrList<type> & list ) const
Compares this list with list. Returns TRUE if the lists contain the
same data; otherwise returns FALSE.
void QPtrList::prepend ( const type * item )
Inserts the item at the start of the list.
The inserted item becomes the current list item. This is equivalent to
insert( 0, item ).
item must not be 0.
See also append(), insert(), and current().
type * QPtrList::prev ()
Returns a pointer to the item preceding the current item. Returns 0 if
the current item is 0 or equal to the first item.
Makes the preceding item current. If the current item before this
function call was the first item, the current item will be set to 0. If
the current item was 0, this function does nothing.
See also first(), last(), next(), and current().
QDataStream & QPtrList::read ( QDataStream & s, QPtrCollection::Item & item )
[virtual protected]
Reads a list item from the stream s and returns a reference to the
stream.
The default implementation sets item to 0.
See also write().
bool QPtrList::remove ( uint index )
Removes the item at position index in the list.
Returns TRUE if successful, i.e. if index is in range; otherwise
returns FALSE. The valid range is 0..(count() - 1) inclusive.
The removed item is deleted if auto-deletion is enabled.
The item after the removed item becomes the new current list item if
the removed item is not the last item in the list. If the last item is
removed, the new last item becomes the current item.
All list iterators that refer to the removed item will be set to point
to the new current item.
See also take(), clear(), setAutoDelete(), current(), and removeRef().
bool QPtrList::remove ()
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Removes the current list item.
Returns TRUE if successful, i.e. if the current item isn't 0; otherwise
returns FALSE.
The removed item is deleted if auto-deletion is enabled.
The item after the removed item becomes the new current list item if
the removed item is not the last item in the list. If the last item is
removed, the new last item becomes the current item. The current item
is set to 0 if the list becomes empty.
All list iterators that refer to the removed item will be set to point
to the new current item.
See also take(), clear(), setAutoDelete(), current(), and removeRef().
bool QPtrList::remove ( const type * item )
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Removes the first occurrence of item from the list.
Returns TRUE if successful, i.e. if item is in the list; otherwise
returns FALSE.
The removed item is deleted if auto-deletion is enabled.
The compareItems() function is called when searching for the item in
the list. If compareItems() is not reimplemented, it is more efficient
to call removeRef().
If item is NULL then the current item is removed from the list.
The item after the removed item becomes the new current list item if
the removed item is not the last item in the list. If the last item is
removed, the new last item becomes the current item. The current item
is set to 0 if the list becomes empty.
All list iterators that refer to the removed item will be set to point
to the new current item.
See also removeRef(), take(), clear(), setAutoDelete(), compareItems(),
and current().
bool QPtrList::removeFirst ()
Removes the first item from the list. Returns TRUE if successful, i.e.
if the list isn't empty; otherwise returns FALSE.
The removed item is deleted if auto-deletion is enabled.
The first item in the list becomes the new current list item. The
current item is set to 0 if the list becomes empty.
All list iterators that refer to the removed item will be set to point
to the new current item.
See also removeLast(), setAutoDelete(), current(), and remove().
bool QPtrList::removeLast ()
Removes the last item from the list. Returns TRUE if successful, i.e.
if the list isn't empty; otherwise returns FALSE.
The removed item is deleted if auto-deletion is enabled.
The last item in the list becomes the new current list item. The
current item is set to 0 if the list becomes empty.
All list iterators that refer to the removed item will be set to point
to the new current item.
See also removeFirst(), setAutoDelete(), and current().
void QPtrList::removeNode ( QLNode * node )
Removes the node from the list.
This node must exist in the list, otherwise the program may crash.
The removed item is deleted if auto-deletion is enabled.
The first item in the list will become the new current list item. The
current item is set to 0 if the list becomes empty.
All list iterators that refer to the removed item will be set to point
to the item succeeding this item or to the preceding item if the
removed item was the last item.
Warning: Do not call this function unless you are an expert.
See also takeNode(), currentNode(), remove(), and removeRef().
bool QPtrList::removeRef ( const type * item )
Removes the first occurrence of item from the list.
Returns TRUE if successful, i.e. if item is in the list; otherwise
returns FALSE.
The removed item is deleted if auto-deletion is enabled.
Equivalent to:
if ( list.findRef( item ) != -1 )
list.remove();
The item after the removed item becomes the new current list item if
the removed item is not the last item in the list. If the last item is
removed, the new last item becomes the current item. The current item
is set to 0 if the list becomes empty.
All list iterators that refer to the removed item will be set to point
to the new current item.
See also remove(), clear(), setAutoDelete(), and current().
bool QPtrList::replace ( uint index, const type * item )
Replaces the item at position index with the new item.
Returns TRUE if successful, i.e. index is in the range 0 to count()-1.
See also append(), current(), and insert().
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:
void QPtrList::sort ()
Sorts the list by the result of the virtual compareItems() function.
The heap sort algorithm is used for sorting. It sorts n items with
O(n*log n) comparisons. This is the asymptotic optimal solution of the
sorting problem.
If the items in your list support operator<() and operator==(), you
might be better off with QSortedList because it implements the
compareItems() function for you using these two operators.
See also inSort().
type * QPtrList::take ( uint index )
Takes the item at position index out of the list without deleting it
(even if auto-deletion is enabled).
Returns a pointer to the item taken out of the list, or 0 if the index
is out of range. The valid range is 0..(count() - 1) inclusive.
The item after the removed item becomes the new current list item if
the removed item is not the last item in the list. If the last item is
removed, the new last item becomes the current item. The current item
is set to 0 if the list becomes empty.
All list iterators that refer to the taken item will be set to point to
the new current item.
See also remove(), clear(), and current().
Examples:
type * QPtrList::take ()
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Takes the current item out of the list without deleting it (even if
auto-deletion is enabled).
Returns a pointer to the item taken out of the list, or 0 if the
current item is 0.
The item after the removed item becomes the new current list item if
the removed item is not the last item in the list. If the last item is
removed, the new last item becomes the current item. The current item
is set to 0 if the list becomes empty.
All list iterators that refer to the taken item will be set to point to
the new current item.
See also remove(), clear(), and current().
type * QPtrList::takeNode ( QLNode * node )
Takes the node out of the list without deleting its item (even if auto-
deletion is enabled). Returns a pointer to the item taken out of the
list.
This node must exist in the list, otherwise the program may crash.
The first item in the list becomes the new current list item.
All list iterators that refer to the taken item will be set to point to
the item succeeding this item or to the preceding item if the taken
item was the last item.
Warning: Do not call this function unless you are an expert.
See also removeNode() and currentNode().
void QPtrList::toVector ( QGVector * vec ) const
Stores all list items in the vector vec.
The vector must be of the same item type, otherwise the result will be
undefined.
QDataStream & QPtrList::write ( QDataStream & s, QPtrCollection::Item item )
const [virtual protected]
Writes a list item, item to the stream s and returns a reference to the
stream.
The default implementation does nothing.
See also read().
SEE ALSO
http://doc.trolltech.com/qptrlist.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports help us to
help you. Thank you.
The definitive Qt documentation is provided in HTML format; it is
located at $QTDIR/doc/html and can be read using Qt Assistant or with a
web browser. This man page is provided as a convenience for those users
who prefer man pages, although this format is not officially supported
by Trolltech.
If you find errors in this manual page, please report them to qt-
bugs@trolltech.com. Please include the name of the manual page
(qptrlist.3qt) and the Qt version (3.3.8).
Trolltech AS 2 February 2007 QPtrList(3qt)
