QMapIterator(3qt)

NAME
QMapIterator - Iterator for

#include <qmap.h>

  Public Members
QMapIterator ()
QMapIterator ( QMapNode<K, T> * p )
QMapIterator ( const QMapIterator<K,T> & it )
bool operator== ( const QMapIterator<K,T> & it ) const
bool operator!= ( const QMapIterator<K,T> & it ) const
T& operator* ()
const T& operator* () const
const K& key () const
T& data ()
const T& data () const

DESCRIPTION
The QMapIterator class provides an iterator for QMap.

You can not create an iterator by yourself. Instead you have to ask a map to give you one. An iterator has only the size of a pointer. On 32 bit machines that means 4 bytes otherwise 8 bytes. That makes them very fast. In fact they resemble the semantics of pointers as good as possible and they are almost as fast as usual pointers.

Example:

    #include <qmap.h>
    #include <qstring.h>
    #include <stdio.h>
    class Employee
    {
    public:
        Employee(): s(0) {}
        Employee( const QString& name, int salary )
            : n(name), s(salary)
        {}
        QString     name()   const              { return n; }
        int         salary() const              { return s; }
        void        setSalary( int salary )     { s = salary; }
    private:
        QString     n;
        int         s;
    };
    void main()
    {
        typedef QMap<QString,Employee> EmployeeMap;
        EmployeeMap map;                // map of Employee
        map.insert( "Gates", Employee("Bill", 50000) );
        map.insert( "Ballmer", Employee("Steve",80000) );
        map.insert( "Sommer,", Employee("Ron",  60000) );
        Employee joe( "Joe", 50000 );
        map.insert( "Doe", joe );
        joe.setSalary( 4000 );
        EmployeeMap::Iterator it;
        for( it = map.begin(); it != map.end(); ++it )
            printf( "%s, %s earns %d\n", it.key().latin1(), it.data().name().latin1(), it.data().salary() );
    }

Program output:

        Ballmer, Steve earns 80000
        Doe, Joe earns 50000
        Gates, Bill earns 50000
        Sommer, Ron earns 60000

The only way to traverse a map is to use iterators. QMap is highly optimized for performance and memory usage. On the other hand that means that you have to be a bit more careful by what you are doing. QMap does not know about all its iterators and the iterators don't even know to which map they belong. That makes things fast and slim but a bit dangerous because it is up to you to make sure that iterators you are using are still valid. QDictIterator will be able to give warnings while QMapIterator may end up in an undefined state.

For every Iterator there is a ConstIterator. When accessing a QMap in a const environment or if the reference or pointer to the map is itself const, then you have to use the ConstIterator. Its semantics are the same, but it returns only const references to the item it points to.

See also QMap.

MEMBER FUNCTION DOCUMENTATION

QMapIterator::QMapIterator ()
Creates an uninitialized iterator.

QMapIterator::QMapIterator ( QMapNode<K, T> * p )
Constructs an iterator starting at node p.

QMapIterator::QMapIterator ( const QMapIterator<K,T> & it )
Constructs a copy of the iterator.

T& QMapIterator::data ()
Returns a reference to the current item.

const T& QMapIterator::data () const
Returns a const reference to the data of the current item.

const K& QMapIterator::key () const
Returns a const reference to the data of the current key.

bool QMapIterator::operator!= ( const QMapIterator<K,T> & it ) const
Compares both iterators and returns TRUE if they point to different items.

T& QMapIterator::operator* ()
Asterix operator. Returns a reference to the current item. The same as data().

const T& QMapIterator::operator* () const
Asterix operator. Returns a const reference to the current item. The same as data().

bool QMapIterator::operator== ( const QMapIterator<K,T> & it ) const
Compares both iterators and returns TRUE if they point to the same item.

SEE ALSO
http://doc.trolltech.com/qmapiterator.html http://www.trolltech.com/faq/tech.html

COPYRIGHT
Copyright 1992-2001 Trolltech AS, 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 make our job much simpler. Thank you.

In case of content or formattting problems with this manual page, please report them to qt-bugs@trolltech.com. Please include the name of the manual page (qmapiterator.3qt) and the Qt version (2.3.1).