/**************************************************************************** ** ** QMap and QMapIterator class documentation ** ** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved. ** ** This file is part of the Qt GUI Toolkit. ** ** This file may be used under the terms of the GNU General ** Public License versions 2.0 or 3.0 as published by the Free ** Software Foundation and appearing in the files LICENSE.GPL2 ** and LICENSE.GPL3 included in the packaging of this file. ** Alternatively you may (at your option) use any later version ** of the GNU General Public License if such license has been ** publicly approved by Trolltech ASA (or its successors, if any) ** and the KDE Free Qt Foundation. ** ** Please review the following information to ensure GNU General ** Public Licensing requirements will be met: ** http://trolltech.com/products/qt/licenses/licensing/opensource/. ** If you are unsure which license is appropriate for your use, please ** review the following information: ** http://trolltech.com/products/qt/licenses/licensing/licensingoverview ** or contact the sales department at sales@trolltech.com. ** ** This file may be used under the terms of the Q Public License as ** defined by Trolltech ASA and appearing in the file LICENSE.QPL ** included in the packaging of this file. Licensees holding valid Qt ** Commercial licenses may use this file in accordance with the Qt ** Commercial License Agreement provided with the Software. ** ** This file is provided "AS IS" with NO WARRANTY OF ANY KIND, ** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR ** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted ** herein. ** **********************************************************************/ /***************************************************************************** QMap documentation *****************************************************************************/ /*! \class QMap qmap.h \brief The QMap class is a value-based template class that provides a dictionary. \ingroup qtl \ingroup tools \ingroup shared \mainclass QMap is a Qt implementation of an STL-like map container. It can be used in your application if the standard \c map is not available on all your target platforms. QMap is part of the \link qtl.html Qt Template Library\endlink. QMap\ 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 \list \i A copy constructor \i An assignment operator \i A default constructor, i.e. a constructor that does not take any arguments. \endlist 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 \c 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 \c map can use these the STL-like functions if preferred. Example: \target qmap-eg \code #include #include #include 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 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\n", it.key().latin1(), it.data().surname().latin1(), it.data().forename().latin1(), it.data().salary() ); } return 0; } \endcode Program output: \code JD001: Doe, John earns 50000 JW002: Williams, Jane earns 80000 SH001: Hind, Sasha earns 50000 TJ001: Jones, Tom earns 60000 \endcode 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 \e 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: \code QMap map; map["Clinton"] = "Bill"; str << map["Clinton"] << map["Bush"] << endl; \endcode 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 \l QMutex. There are a couple of ways of inserting new items into the map. One uses the insert() method; the other uses operator[]: \code QMap map; map["Clinton"] = "Bill"; map.insert( "Bush", "George" ); \endcode 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. \sa QMapIterator */ /*! \enum QMap::key_type The map's key type. */ /*! \enum QMap::mapped_type The map's data type. */ /*! \enum QMap::value_type Corresponds to QPair\. */ /*! \enum QMap::ValueType Corresponds to QPair\, Qt style.*/ /*! \enum QMap::pointer Pointer to value_type.*/ /*! \enum QMap::const_pointer Const pointer to value_type.*/ /*! \enum QMap::reference Reference to value_type.*/ /*! \enum QMap::const_reference Const reference to value_type.*/ /*! \enum QMap::size_type An unsigned integral type, used to represent various sizes. */ /*! \enum QMap::iterator The map's iterator type.*/ /*! \enum QMap::Iterator The map's iterator type, Qt style. */ /*! \enum QMap::const_iterator The map's const iterator type.*/ /*! \enum QMap::ConstIterator The map's const iterator type, Qt style.*/ /*! \enum QMap::difference_type \internal */ /*! \enum QMap::Priv \internal */ /*! \fn QMap::QMap() Constructs an empty map. */ /*! \fn QMap::QMap( const QMap& m ) Constructs a copy of \a 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. */ /*! \fn QMap::QMap( const std::map& m ) Constructs a copy of \a m. */ /*! \fn QMap& QMap::operator= ( const std::map& m ) \overload Assigns \a m to this map and returns a reference to this map. All iterators of the current map become invalidated by this operation. */ /*! \fn 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. */ /*! \fn QMap& QMap::operator= (const QMap& m) Assigns \a 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. */ /*! \fn T& QMap::operator[] ( const Key& k ) Returns the value associated with the key \a 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: \code QMap map; map["Clinton"] = "Bill"; stream << map["Clinton"]; \endcode */ /*! \fn void QMap::clear() Removes all items from the map. \sa remove() */ /*! \fn Iterator QMap::find( const Key& k ) Returns an iterator pointing to the element with key \a k in the map. Returns end() if no key matched. \sa QMapIterator */ /*! \fn ConstIterator QMap::find( const Key& k ) const \overload Returns an iterator pointing to the element with key \a k in the map. Returns end() if no key matched. \sa QMapConstIterator */ /*! \fn 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). \sa end() QMapIterator */ /*! \fn ConstIterator QMap::begin() const \overload \sa end() QMapConstIterator */ /*! \fn ConstIterator QMap::constBegin() const 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). \sa constEnd() QMapConstIterator */ /*! \fn 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 \e not dereferenceable; operator*() will not return a well-defined value. This iterator equals begin() if the map is empty. \sa begin() QMapIterator */ /*! \fn ConstIterator QMap::end() const \overload */ /*! \fn ConstIterator QMap::constEnd() const 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 \e not dereferenceable; operator*() will not return a well-defined value. This iterator equals constBegin() if the map is empty. \sa constBegin() QMapConstIterator */ /*! \fn void QMap::detach() 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. */ /*! \fn QDataStream& operator>>( QDataStream& s, QMap& m ) \relates QMap Reads the map \a m from the stream \a s. The types \e Key and \e T must implement the streaming operator as well. */ /*! \fn QDataStream& operator<<( QDataStream& s, const QMap& m ) \relates QMap Writes the map \a m to the stream \a s. The types \e Key and \e T must implement the streaming operator as well. */ /*! \fn 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(). \sa empty() */ /*! \fn 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(). \sa size() */ /*! \fn QPair QMap::insert( const value_type& x ) \overload Inserts the (key, value) pair \a x into the map. \a x is a QPair whose \c first element is a key to be inserted and whose \c second element is the associated value to be inserted. Returns a pair whose \c first element is an iterator pointing to the inserted item and whose \c second element is a bool indicating TRUE if \a x was inserted and FALSE if it was not inserted, e.g. because it was already present. \sa replace() */ /*! \fn void QMap::erase( iterator it ) Removes the item associated with the iterator \a it from the map. This function is provided for STL compatibility. It is equivalent to remove(). \sa clear() */ /*! \fn void QMap::erase( const key_type& k ) \overload Removes the item with the key \a k from the map. */ /*! \fn size_type QMap::count( const key_type& k ) const Returns the number of items whose key is \a k. Since QMap does not allow duplicate keys, the return value is always 0 or 1. This function is provided for STL compatibility. */ /*! \fn Iterator QMap::replace( const Key& k, const T& v ) Replaces the value of the element with key \a k, with the value \a v. \sa insert() remove() */ /*! \fn const T& QMap::operator[] ( const Key& k ) const \overload \warning This function differs from the non-const version of the same function. It will \e not insert an empty value if the key \a 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 \a k. If no such key is present, a reference to an empty item is returned. */ /*! \fn uint QMap::count() const \overload Returns the number of items in the map. \sa isEmpty() */ /*! \fn bool QMap::isEmpty() const Returns TRUE if the map contains no items; otherwise returns FALSE. \sa count() */ /*! \fn Iterator QMap::insert( const Key& key, const T& value, bool overwrite ) Inserts a new item with the key, \a key, and a value of \a value. If there is already an item whose key is \a key, that item's value is replaced with \a value, unless \a overwrite is FALSE (it is TRUE by default). In this case an iterator to this item is returned, else an iterator to the new item is returned. */ /*! \fn void QMap::remove( iterator it ) Removes the item associated with the iterator \a it from the map. \sa clear() */ /*! \fn void QMap::remove( const Key& k ) \overload Removes the item with the key \a k from the map. */ /*! \fn bool QMap::contains( const Key& k ) const Returns TRUE if the map contains an item with key \a k; otherwise returns FALSE. */ /***************************************************************************** QMapIterator documentation *****************************************************************************/ /*! \class QMapIterator qmap.h \brief The QMapIterator class provides an iterator for QMap. \ingroup qtl \ingroup tools You cannot create an iterator by yourself. Instead, you must ask a map to give you one. An iterator is as big as a pointer; on 32-bit machines that means 4 bytes, on 64-bit machines, 8 bytes. That makes copying iterators very fast. Iterators behave in a similar way to pointers, and they are almost as fast as pointers. See the \link qmap.html#qmap-eg QMap example\endlink. QMap is highly optimized for performance and memory usage, but the trade-off is that you must be more careful. The only way to traverse a map is to use iterators. QMap does not know about its iterators, and the iterators don't even know to which map they belong. That makes things fast but a bit dangerous because it is up to you to make sure that the iterators you are using are still valid. QDictIterator will be able to give warnings, whereas QMapIterator may end up in an undefined state. For every Iterator there is also a ConstIterator. You must use the ConstIterator to access a QMap in a const environment or if the reference or pointer to the map is itself const. Its semantics are the same, but it only returns const references to the item it points to. \sa QMap QMapConstIterator */ /*! \enum QMapIterator::iterator_category The type of iterator category, \c std::bidirectional_iterator_tag. */ /*! \enum QMapIterator::value_type The type of value. */ /*! \enum QMapIterator::pointer Pointer to value_type. */ /*! \enum QMapIterator::reference Reference to value_type. */ /*! \enum QMapIterator::difference_type \internal */ /*! \enum QMapIterator::NodePtr \internal */ /*! \fn QMapIterator::QMapIterator() Creates an uninitialized iterator. */ /*! \fn QMapIterator::QMapIterator (QMapNode * p) Constructs an iterator starting at node \a p. */ /*! \fn QMapIterator::QMapIterator( const QMapIterator& it ) Constructs a copy of the iterator, \a it. */ /*! \fn QMapIterator& QMapIterator::operator++() Prefix ++ makes the succeeding item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the end of the map. Incrementing the iterator returned by end() causes undefined results. */ /*! \fn QMapIterator QMapIterator::operator++(int) \overload Postfix ++ makes the succeeding item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the end of the map. Incrementing the iterator returned by end() causes undefined results. */ /*! \fn QMapIterator& QMapIterator::operator--() Prefix -- makes the previous item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the beginning of the map. Decrementing the iterator returned by begin() causes undefined results. */ /*! \fn QMapIterator QMapIterator::operator--(int) \overload Postfix -- makes the previous item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the beginning of the map. Decrementing the iterator returned by begin() causes undefined results. */ /*! \fn T& QMapIterator::operator*() Dereference operator. Returns a reference to the current item's data. The same as data(). */ /*! \fn const T& QMapIterator::operator*() const \overload Dereference operator. Returns a const reference to the current item's data. The same as data(). */ /*! \fn bool QMapIterator::operator==( const QMapIterator& it ) const Compares the iterator to the \a it iterator and returns TRUE if they point to the same item; otherwise returns FALSE. */ /*! \fn bool QMapIterator::operator!=( const QMapIterator& it ) const Compares the iterator to the \a it iterator and returns FALSE if they point to the same item; otherwise returns TRUE. */ /*! \fn T& QMapIterator::data() Returns a reference to the current item's data. */ /*! \fn const T& QMapIterator::data() const \overload Returns a const reference to the current item's data. */ /*! \fn const K& QMapIterator::key() const Returns a const reference to the current item's key. */ /*! \fn QValueList QMap::keys() const Returns a list of all the keys in the map, in order. */ /*! \fn QValueList QMap::values() const Returns a list of all the values in the map, in key order. */ /***************************************************************************** QMapConstIterator documentation *****************************************************************************/ /*! \class QMapConstIterator qmap.h \brief The QMapConstIterator class provides an iterator for QMap. \ingroup qtl \ingroup tools In contrast to QMapIterator, this class is used to iterate over a const map. It does not allow you to modify the values of the map because this would break the const semantics. For more information on QMap iterators, see \l{QMapIterator} and the \link qmap.html#qmap-eg QMap example\endlink. \sa QMap QMapIterator */ /*! \enum QMapConstIterator::iterator_category The type of iterator category, \c std::bidirectional_iterator_tag. */ /*! \enum QMapConstIterator::value_type The type of const value. */ /*! \enum QMapConstIterator::pointer Const pointer to value_type. */ /*! \enum QMapConstIterator::reference Const reference to value_type. */ /*! \enum QMapConstIterator::difference_type \internal */ /*! \enum QMapConstIterator::NodePtr \internal */ /*! \fn QMapConstIterator::QMapConstIterator() Constructs an uninitialized iterator. */ /*! \fn QMapConstIterator::QMapConstIterator (QMapNode * p) Constructs an iterator starting at node \a p. */ /*! \fn QMapConstIterator::QMapConstIterator( const QMapConstIterator& it ) Constructs a copy of the iterator, \a it. */ /*! \fn QMapConstIterator::QMapConstIterator( const QMapIterator& it ) Constructs a copy of the iterator, \a it. */ /*! \fn QMapConstIterator& QMapConstIterator::operator++() Prefix ++ makes the succeeding item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the end of the map. Incrementing the iterator returned by end() causes undefined results. */ /*! \fn QMapConstIterator QMapConstIterator::operator++(int) \overload Postfix ++ makes the succeeding item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the end of the map. Incrementing the iterator returned by end() causes undefined results. */ /*! \fn QMapConstIterator& QMapConstIterator::operator--() Prefix -- makes the previous item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the beginning of the map. Decrementing the iterator returned by begin() causes undefined results. */ /*! \fn QMapConstIterator QMapConstIterator::operator--(int) \overload Postfix -- makes the previous item current and returns an iterator pointing to the new current item. The iterator cannot check whether it reached the beginning of the map. Decrementing the iterator returned by begin() causes undefined results. */ /*! \fn const T& QMapConstIterator::operator*() const Dereference operator. Returns a const reference to the current item's data. The same as data(). */ /*! \fn bool QMapConstIterator::operator==( const QMapConstIterator& it ) const Compares the iterator to the \a it iterator and returns TRUE if they point to the same item; otherwise returns FALSE. */ /*! \fn bool QMapConstIterator::operator!=( const QMapConstIterator& it ) const Compares the iterator to the \a it iterator and returns FALSE if they point to the same item; otherwise returns TRUE. */ /*! \fn const T& QMapConstIterator::data() const Returns a const reference to the current item's data. */ /*! \fn const K& QMapConstIterator::key() const Returns a const reference to the current item's key. */