QMap(3qt)																 QMap(3qt)

NAME

       QMap - Value-based template class that provides a dictionary

SYNOPSIS

       #include <qmap.h>

   Public Members
       typedef Key key_type
       typedef T mapped_type
       typedef QPair<const key_type, mapped_type> value_type
       typedef value_type * pointer
       typedef const value_type * const_pointer
       typedef value_type & reference
       typedef const value_type & const_reference
       typedef size_t size_type
       typedef QMapIterator<Key, T> iterator
       typedef QMapConstIterator<Key, T> const_iterator
       typedef QPair<iterator, bool> insert_pair
       typedef QMapIterator<Key, T> Iterator
       typedef QMapConstIterator<Key, T> ConstIterator
       typedef T ValueType
       QMap ()
       QMap ( const QMap<Key, T> & m )
       QMap ( const std::map<Key, T> & m )
       ~QMap ()
       QMap<Key, T> & operator= ( const QMap<Key, T> & m )
       QMap<Key, T> & operator= ( const std::map<Key, T> & m )
       iterator begin ()
       iterator end ()
       const_iterator begin () const
       const_iterator end () const
       iterator replace ( const Key & k, const T & v )
       size_type size () const
       bool empty () const
       QPair<iterator, bool> insert ( const value_type & x )
       void erase ( iterator it )
       void erase ( const key_type & k )
       size_type count ( const key_type & k ) const
       T & operator[] ( const Key & k )
       void clear ()
       iterator find ( const Key & k )
       const_iterator find ( const Key & k ) const
       const T & operator[] ( const Key & k ) const
       bool contains ( const Key & k ) const
       size_type count () const
       QValueList<Key> keys () const
       QValueList<T> values () const
       bool isEmpty () const
       iterator insert ( const Key & key, const T & value, bool overwrite = TRUE )
       void remove ( iterator it )
       void remove ( const Key & k )

   Protected Members
       void detach ()

RELATED FUNCTION DOCUMENTATION

       QDataStream & operator>> ( QDataStream & s, QMap<Key, T> & m )
       QDataStream & operator<< ( QDataStream & s, const QMap<Key, T> & m )

DESCRIPTION

       The QMap class is a value-based template class that provides a dictionary.

       QMap is a Qt implementation of an STL-like map container. It can be used in your application if the standard map is not available on all
       your target platforms. QMap is part of the Qt Template Library.

       QMap<Key, Data> defines a template instance to create a dictionary with keys of type Key and values of type Data. QMap does not store
       pointers to the members of the map; instead, it holds a copy of every member. For this reason, QMap is value-based, whereas QPtrList and
       QDict are pointer-based.

       QMap contains and manages a collection of objects of type Data with associated key values of type Key and provides iterators that allow the
       contained objects to be addressed. QMap owns the contained items.

       Some classes cannot be used within a QMap. For example everything derived from QObject and thus all classes that implement widgets. Only
       values can be used in a QMap. To qualify as a value, the class must provide

       A copy constructor

       An assignment operator

       A default constructor, i.e. a constructor that does not take any arguments.

       Note that C++ defaults to field-by-field assignment operators and copy constructors if no explicit version is supplied. In many cases, this
       is sufficient.

       The class used for the key requires that the operator< is implemented to define ordering of the keys.

       QMap's function naming is consistent with the other Qt classes (e.g., count(), isEmpty()). QMap also provides extra functions for
       compatibility with STL algorithms, such as size() and empty(). Programmers already familiar with the STL map can use these the STL-like
       functions if preferred.

       Example:

	   #include <qstring.h>
	   #include <qmap.h>
	   #include <qstring.h>
	   class Employee
	   {
	   public:
	       Employee(): sn(0) {}
	       Employee( const QString& forename, const QString& surname, int salary )
		   : fn(forename), sn(surname), sal(salary)
	       { }
	       QString forename() const { return fn; }
	       QString surname() const { return sn; }
	       int salary() const { return sal; }
	       void setSalary( int salary ) { sal = salary; }
	   private:
	       QString fn;
	       QString sn;
	       int sal;
	   };
	   int main(int argc, char **argv)
	   {
	       QApplication app( argc, argv );
	       typedef QMap<QString, Employee> EmployeeMap;
	       EmployeeMap map;
	       map["JD001"] = Employee("John", "Doe", 50000);
	       map["JW002"] = Employee("Jane", "Williams", 80000);
	       map["TJ001"] = Employee("Tom", "Jones", 60000);
	       Employee sasha( "Sasha", "Hind", 50000 );
	       map["SH001"] = sasha;
	       sasha.setSalary( 40000 );
	       EmployeeMap::Iterator it;
	       for ( it = map.begin(); it != map.end(); ++it ) {
		   printf( "%s: %s, %s earns %d
",
			   it.key().latin1(),
			   it.data().surname().latin1(),
			   it.data().forename().latin1(),
			   it.data().salary() );
	       }
	       return 0;
	   }

       Program output:

	   JD001: Doe, John earns 50000
	   JW002: Williams, Jane earns 80000
	   SH001: Hind, Sasha earns 50000
	   TJ001: Jones, Tom earns 60000

       The latest changes to Sasha's salary did not affect the value in the list because the map created a copy of Sasha's entry. In addition,
       notice that the items are sorted alphabetically (by key) when iterating over the map.

       There are several ways to find items in a map. The begin() and end() functions return iterators to the beginning and end of the map. The
       advantage of using an iterator is that you can move forward or backward by incrementing/decrementing the iterator. The iterator returned by
       end() points to the element which is one past the last element in the container. The past-the-end iterator is still associated with the map
       it belongs to, however it is not dereferenceable; operator*() will not return a well-defined value. If the map is empty, the iterator
       returned by begin() will equal the iterator returned by end().

       Another way to find an element in the map is by using the find() function. This returns an iterator pointing to the desired item or to the
       end() iterator if no such element exists.

       Another approach uses the operator[]. But be warned: if the map does not contain an entry for the element you are looking for, operator[]
       inserts a default value. If you do not know that the element you are searching for is really in the list, you should not use operator[].
       The following example illustrates this:

	       QMap<QString,QString> map;
	       map["Clinton"] = "Bill";
	       str << map["Clinton"] << map["Bush"] << endl;

       The code fragment will print out "Clinton", "". Since the value associated with the "Bush" key did not exist, the map inserted a default
       value (in this case, an empty string). If you are not sure whether a certain element is in the map, you should use find() and iterators
       instead.

       If you just want to know whether a certain key is contained in the map, use the contains() function. In addition, count() tells you how
       many keys are in the map.

       It is safe to have multiple iterators at the same time. If some member of the map is removed, only iterators pointing to the removed member
       become invalid; inserting in the map does not invalidate any iterators.

       Since QMap is value-based, there is no need to be concerned about deleting items in the map. The map holds its own copies and will free
       them if the corresponding member or the map itself is deleted.

       QMap is implicitly shared. This means you can just make copies of the map in time O(1). If multiple QMap instances share the same data and
       one is modifying the map's data, this modifying instance makes a copy and modifies its private copy: so it does not affect other instances.
       If a QMap is being used in a multi-threaded program, you must protect all access to the map. See QMutex.

       There are a couple of ways of inserting new items into the map. One uses the insert() method; the other uses operator[]:

	   QMap<QString, QString> map;
	   map["Clinton"] = "Bill";
	   map.insert( qMakePair("Bush", "George") );

       Items can also be removed from the map in several ways. One way is to pass an iterator to remove(). Another way is to pass a key value to
       remove(), which will delete the entry with the requested key. In addition you can clear the entire map using the clear() method.

       See also QMapIterator, Qt Template Library Classes, Implicitly and Explicitly Shared Classes, and Non-GUI Classes.

   Member Type Documentation
QMap::ConstIterator
       The map's const iterator type, Qt style.

QMap::Iterator
       The map's iterator type, Qt style.

QMap::ValueType
       Corresponds to QPair<key_type, mapped_type>, Qt style.

QMap::const_iterator
       The map's const iterator type.

QMap::const_pointer
       Const pointer to value_type.

QMap::const_reference
       Const reference to value_type.

QMap::iterator
       The map's iterator type.

QMap::key_type
       The map's key type.

QMap::mapped_type
       The map's data type.

QMap::pointer
       Pointer to value_type.

QMap::reference
       Reference to value_type.

QMap::size_type
       An unsigned integral type, used to represent various sizes.

QMap::value_type
       Corresponds to QPair<key_type, mapped_type>.

MEMBER FUNCTION DOCUMENTATION

QMap::QMap ()
       Constructs an empty map.

QMap::QMap ( const QMap<Key, T> & m )
       Constructs a copy of m.

       This operation costs O(1) time because QMap is implicitly shared. This makes returning a QMap from a function very fast. If a shared
       instance is modified, it will be copied (copy-on-write), and this takes O(n) time.

QMap::QMap ( const std::map<Key, T> & m )
       Constructs a copy of m.

QMap::~QMap ()
       Destroys the map. References to the values in the map and all iterators of this map become invalidated. Since QMap is highly tuned for
       performance you won't see warnings if you use invalid iterators, because it is not possible for an iterator to check whether it is valid or
       not.

iterator QMap::begin ()
       Returns an iterator pointing to the first element in the map. This iterator equals end() if the map is empty.

       The items in the map are traversed in the order defined by operator<(Key, Key).

       See also end() and QMapIterator.

const_iterator QMap::begin () const
       This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

       See also end() and QMapConstIterator.

void QMap::clear ()
       Removes all items from the map.

       See also remove().

bool QMap::contains ( const Key & k ) const
       Returns TRUE if the map contains an item with key k; otherwise returns FALSE.

size_type QMap::count ( const key_type & k ) const
       Returns the number of items whose key is k. Since QMap does not allow duplicate keys, the return value is always 0 or 1.

       This function is provided for STL compatibility.

size_type QMap::count () const
       This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

       Returns the number of items in the map.

       See also isEmpty().

void QMap::detach () [protected]
       If the map does not share its data with another QMap instance, nothing happens; otherwise the function creates a new copy of this map and
       detaches from the shared one. This function is called whenever the map is modified. The implicit sharing mechanism is implemented this way.

bool QMap::empty () const
       Returns TRUE if the map contains no items; otherwise returns FALSE.

       This function is provided for STL compatibility. It is equivalent to isEmpty().

       See also size().

iterator QMap::end ()
       The iterator returned by end() points to the element which is one past the last element in the container. The past-the-end iterator is
       still associated with the map it belongs to, but it is not dereferenceable; operator*() will not return a well-defined value.

       This iterator equals begin() if the map is empty.

       See also begin() and QMapIterator.

const_iterator QMap::end () const
       This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

void QMap::erase ( iterator it )
       Removes the item associated with the iterator it from the map.

       This function is provided for STL compatibility. It is equivalent to remove().

       See also clear().

void QMap::erase ( const key_type & k )
       This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

       Removes the item with the key k from the map.

iterator QMap::find ( const Key & k )
       Returns an iterator pointing to the element with key k in the map.

       Returns end() if no key matched.

       See also QMapIterator.

const_iterator QMap::find ( const Key & k ) const
       This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

       Returns an iterator pointing to the element with key k in the map.

       Returns end() if no key matched.

       See also QMapConstIterator.

iterator QMap::insert ( const Key & key, const T & value, bool overwrite = TRUE )
       Inserts a new item with the key, key, and a value of value. If there is already an item whose key is key, that item's value is replaced
       with value, unless overwrite is FALSE (it is TRUE by default).

QPair<;iterator, bool> QMap::insert ( const value_type & x )
       This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

       Inserts the (key, value) pair x into the map. x is a QPair whose first element is a key to be inserted and whose second element is the
       associated value to be inserted. Returns a pair whose first element is an iterator pointing to the inserted item and whose second element
       is a bool indicating TRUE if x was inserted and FALSE if it was not inserted, e.g. because it was already present.

       See also replace().

bool QMap::isEmpty () const
       Returns TRUE if the map contains no items; otherwise returns FALSE.

       See also count().

QValueList<;Key> QMap::keys () const
       Returns a list of all the keys in the map.

QMap<;Key, T> & QMap::operator= ( const QMap<Key, T> & m )
       Assigns m to this map and returns a reference to this map.

       All iterators of the current map become invalidated by this operation. The cost of such an assignment is O(1), because QMap is implicitly
       shared.

QMap<;Key, T> & QMap::operator= ( const std::map<Key, T> & m )
       This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

       Assigns m to this map and returns a reference to this map.

       All iterators of the current map become invalidated by this operation.

T &; QMap::operator[] ( const Key & k )
       Returns the value associated with the key k. If no such key is present, an empty item is inserted with this key and a reference to the
       empty item is returned.

       You can use this operator both for reading and writing:

	   QMap<QString, QString> map;
	   map["Clinton"] = "Bill";
	   stream << map["Clinton"];

const T &; QMap::operator[] ( const Key & k ) const
       This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

       Warning: This function differs from the non-const version of the same function. It will not insert an empty value if the key k does not
       exist. This may lead to logic errors in your program. You should check if the element exists before calling this function.

       Returns the value associated with the key k. If no such key is present, a reference to an empty item is returned.

void QMap::remove ( iterator it )
       Removes the item associated with the iterator it from the map.

       See also clear().

void QMap::remove ( const Key & k )
       This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

       Removes the item with the key k from the map.

iterator QMap::replace ( const Key & k, const T & v )
       Replaces the value of the element with key k, with the value v.

       See also insert() and remove().

size_type QMap::size () const
       Returns the number of items in the map.

       This function is provided for STL compatibility. It is equivalent to count().

       See also empty().

QValueList<;T> QMap::values () const
       Returns a list of all the values in the map.

RELATED FUNCTION DOCUMENTATION

QDataStream &; operator<< ( QDataStream & s, const QMap<Key, T> & m )
       Writes the map m to the stream s. The types Key and T must implement the streaming operator as well.

QDataStream &; operator>> ( QDataStream & s, QMap<Key, T> & m )
       Reads the map m from the stream s. The types Key and T must implement the streaming operator as well.

SEE ALSO

       http://doc.trolltech.com/qmap.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 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 (qmap.3qt)
       and the Qt version (3.1.1).

Trolltech AS							  9 December 2002							 QMap(3qt)