Материал из Wiki.crossplatform.ru

Внимание: Актуальная версия перевода документации находится здесь

__NOTOC__

[править] Q3PtrListIterator Class Reference
^{[ Qt3Support module]}

The Q3PtrListIterator class provides an iterator for Q3PtrList collections. Далее...

 #include <Q3PtrListIterator>

This class is part of the Qt 3 support library. It is provided to keep old source code working. Мы настоятельно не рекомендуем использовать этот класс в новом коде. See Porting to Qt 4 for more information.

Inherited by Q3StrListIterator.

• Список всех членов, включая унаследованные

[править] Открытые функции

• Q3PtrListIterator ( const Q3PtrList<type> & list )
• ~Q3PtrListIterator ()
• bool atFirst () const
• bool atLast () const
• uint count () const
• type * current () const
• bool isEmpty () const
• type * toFirst ()
• type * toLast ()
• operator type * () const
• type * operator() ()
• type * operator* ()
• type * operator++ ()
• type * operator+= ( uint jump )
• type * operator-- ()
• type * operator-= ( uint jump )
• Q3PtrListIterator<type> & operator= ( const Q3PtrListIterator<type> & it )

[править] Подробное описание

The Q3PtrListIterator class provides an iterator for Q3PtrList collections.

Define a template instance Q3PtrListIterator<X> to create a list iterator that operates on Q3PtrList<X> (list of X*).

The following example is similar to the example in the Q3PtrList class documentation, but it uses Q3PtrListIterator. The class Employee is defined there.

 Q3PtrList<Employee> list;
 
 list.append( new Employee("John", "Doe", 50000) );
 list.append( new Employee("Jane", "Williams", 80000) );
 list.append( new Employee("Tom", "Jones", 60000) );
 
 Q3PtrListIterator<Employee> it( list );
 Employee *employee;
 while ( (employee = it.current()) != 0 ) {
     ++it;
     cout << employee->surname().latin1() << ", " <<
             employee->forename().latin1() << " earns " <<
             employee->salary() << endl;
 }

The output is

 Doe, John earns 50000
 Williams, Jane earns 80000
 Jones, Tom earns 60000

Using a list iterator is a more robust way of traversing the list than using the Q3PtrList member functions first(), next(), current(), etc., as many iterators can traverse the same list independently.

An iterator has its own current list item and can get the next and previous list items. It doesn't modify the list in any way.

When an item is removed from the list, all iterators that point to that item are updated to point to Q3PtrList::current() instead to avoid dangling references.

See also Q3PtrList.

[править] Описание функций-членов

[править]

Q3PtrListIterator::Q3PtrListIterator ( const Q3PtrList<type> & list )

Constructs an iterator for list. The current iterator item is set to point on the first item in the list.

[править]

Q3PtrListIterator::~Q3PtrListIterator ()

Destroys the iterator.

[править]

bool Q3PtrListIterator::atFirst () const

Returns TRUE if the current iterator item is the first list item; otherwise returns FALSE.

See also toFirst() and atLast().

[править]

bool Q3PtrListIterator::atLast () const

Returns TRUE if the current iterator item is the last list item; otherwise returns FALSE.

See also toLast() and atFirst().

[править]

uint Q3PtrListIterator::count () const

Returns the number of items in the list this iterator operates on.

See also isEmpty().

[править]

type * Q3PtrListIterator::current () const

Returns a pointer to the current iterator item. If the iterator is positioned before the first item in the list or after the last item in the list, 0 is returned.

[править]

bool Q3PtrListIterator::isEmpty () const

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

Смотрите также count().

[править]

type * Q3PtrListIterator::toFirst ()

Sets the current iterator item to point to the first list item and returns a pointer to the item. Sets the current item to 0 and returns 0 if the list is empty.

See also toLast() and atFirst().

[править]

type * Q3PtrListIterator::toLast ()

Sets the current iterator item to point to the last list item and returns a pointer to the item. Sets the current item to 0 and returns 0 if the list is empty.

See also toFirst() and atLast().

[править]

Q3PtrListIterator::operator type * () const

Cast operator. Returns a pointer to the current iterator item. Same as current().

[править]

type * Q3PtrListIterator::operator() ()

Makes the succeeding item current and returns the original current item.

If the current iterator item was the last item in the list or if it was 0, 0 is returned.

[править]

type * Q3PtrListIterator::operator* ()

Asterisk operator. Returns a pointer to the current iterator item. Same as current().

[править]

type * Q3PtrListIterator::operator++ ()

Prefix ++ makes the succeeding item current and returns the new current item.

If the current iterator item was the last item in the list or if it was 0, 0 is returned.

[править]

type * Q3PtrListIterator::operator+= ( uint jump )

Sets the current item to the item jump positions after the current item and returns a pointer to that item.

If that item is beyond the last item or if the list is empty, it sets the current item to 0 and returns 0

[править]

type * Q3PtrListIterator::operator-- ()

Prefix - makes the preceding item current and returns the new current item.

If the current iterator item was the first item in the list or if it was 0, 0 is returned.

[править]

type * Q3PtrListIterator::operator-= ( uint jump )

Returns the item jump positions before the current item or 0 if it is beyond the first item. Makes this the current item.

[править]

Q3PtrListIterator<type> & Q3PtrListIterator::operator= ( const Q3PtrListIterator<type> & it )

Assignment. Makes a copy of the iterator it and returns a reference to this iterator.