QPtrListIterator Class

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# QPtrListIterator Class Reference

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

`#include <qptrlist.h>`

Inherited by QObjectListIterator 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.

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

## 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.

See also toFirst() and atLast().

### bool QPtrListIterator::atLast () const

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

See also toLast() and atFirst().

### uint QPtrListIterator::count () const

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

See also isEmpty().

Example: customlayout/card.cpp.

### 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, 0 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.

See also count().

### 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 0, 0 is returned.

### type * QPtrListIterator::operator* ()

Asterisk 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 0, 0 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 0 and returns 0

### 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 0, 0 is returned.

### type * QPtrListIterator::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.

### 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 0 and returns 0 if the list is empty.

See also toLast() and atFirst().

### 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 0 and returns 0 if the list is empty.

See also toFirst() and atLast().

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