QPtrListIterator Class Reference

The QPtrListIterator class provides an iterator for QPtrList collections. More...

#include <qptrlist.h>

Inherited by QObjectListIt and QStrListIterator.

List of all member functions.

Public Members

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

Detailed Description

The QPtrListIterator class provides an iterator for QPtrList collections.

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

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

    QPtrList<Employee> list;

    list.append( new Employee("John", "Doe", 50000) );
    list.append( new Employee("Jane", "Williams", 80000) );
    list.append( new Employee("Tom", "Jones", 60000) );

    QPtrListIterator<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 QPtrList 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 QPtrList::current() instead to avoid dangling references.

Member Function Documentation

QPtrListIterator::QPtrListIterator ( const QPtrList<type> & list )

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

QPtrListIterator::~QPtrListIterator ()

Destroys the iterator.

bool QPtrListIterator::atFirst () const

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

bool QPtrListIterator::atLast () const

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

uint QPtrListIterator::count () const

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

type * QPtrListIterator::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, a null is returned.

Examples: canvas/canvas.cpp, customlayout/card.cpp and customlayout/flow.cpp.

bool QPtrListIterator::isEmpty () const

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

QPtrListIterator::operator type * () const

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

type * QPtrListIterator::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 null, null is returned.

type * QPtrListIterator::operator* ()

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

type * QPtrListIterator::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 null, null is returned.

type * QPtrListIterator::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 null and returns null

type * QPtrListIterator::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 null, null is returned.

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

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

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

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

type * QPtrListIterator::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 null and returns null if the list is empty.

type * QPtrListIterator::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 null and returns null if the list is empty.