/**************************************************************************** ** ** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo ** Copyright (C) 2020 The Qt Company Ltd. ** Contact: https://www.qt.io/licensing/ ** ** This file is part of the QtCore module of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:LGPL$ ** Commercial License Usage ** Licensees holding valid commercial Qt licenses may use this file in ** accordance with the commercial license agreement provided with the ** Software or, alternatively, in accordance with the terms contained in ** a written agreement between you and The Qt Company. For licensing terms ** and conditions see https://www.qt.io/terms-conditions. For further ** information use the contact form at https://www.qt.io/contact-us. ** ** GNU Lesser General Public License Usage ** Alternatively, this file may be used under the terms of the GNU Lesser ** General Public License version 3 as published by the Free Software ** Foundation and appearing in the file LICENSE.LGPL3 included in the ** packaging of this file. Please review the following information to ** ensure the GNU Lesser General Public License version 3 requirements ** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. ** ** GNU General Public License Usage ** Alternatively, this file may be used under the terms of the GNU ** General Public License version 2.0 or (at your option) the GNU General ** Public license version 3 or any later version approved by the KDE Free ** Qt Foundation. The licenses are as published by the Free Software ** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 ** included in the packaging of this file. Please review the following ** information to ensure the GNU General Public License requirements will ** be met: https://www.gnu.org/licenses/gpl-2.0.html and ** https://www.gnu.org/licenses/gpl-3.0.html. ** ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \class QMultiMap \inmodule QtCore \brief The QMultiMap class is a template class that provides an associative array with multiple equivalent keys. \ingroup tools \ingroup shared \reentrant QMultiMap\ is one of Qt's generic \l{container classes}. It stores (key, value) pairs and provides fast lookup by key. QMultiMap and QMultiHash provide very similar functionality. The differences are: \list \li QMultiHash provides average faster lookups than QMultiMap. (See \l{Algorithmic Complexity} for details.) \li When iterating over a QMultiHash, the items are arbitrarily ordered. With QMultiMap, the items are always sorted by key. \li The key type of a QMultiHash must provide operator==() and a global qHash(Key) function. The key type of a QMultiMap must provide operator<() specifying a total order. Since Qt 5.8.1 it is also safe to use a pointer type as key, even if the underlying operator<() does not provide a total order. \endlist Here's an example QMultiMap with QString keys and \c int values: \snippet code/src_corelib_tools_qmultimap.cpp 0 To insert a (key, value) pair into the multi map, you can use insert(): \snippet code/src_corelib_tools_qmultimap.cpp 2 This inserts the following three (key, value) pairs into the QMultiMap: ("a", 1), ("b", 3), ("c", 7), and ("c", -5); note that duplicate keys are allowed. To look up a value, use find() or value(): \snippet code/src_corelib_tools_qmultimap.cpp 3 If there is no item with the specified key in the map, these functions return a \l{default-constructed value}. If you want to check whether the map contains a certain key, use contains(): \snippet code/src_corelib_tools_qmultimap.cpp 4 There is also a value() overload that uses its second argument as a default value if there is no item with the specified key: \snippet code/src_corelib_tools_qmultimap.cpp 5 If you want to navigate through all the (key, value) pairs stored in a QMultiMap, you can use an iterator. QMultiMap provides both \l{Java-style iterators} (QMultiMapIterator and QMutableMultiMapIterator) and \l{STL-style iterators} (QMultiMap::const_iterator and QMultiMap::iterator). Here's how to iterate over a QMultiMap using a Java-style iterator: \snippet code/src_corelib_tools_qmultimap.cpp 7 Here's the same code, but using an STL-style iterator this time: \snippet code/src_corelib_tools_qmultimap.cpp 8 The items are traversed in ascending key order. A QMultiMap allows multiple values per key. If you call insert() with a key that already exists in the map, a new (key, value) pair will be inserted. For example: \snippet code/src_corelib_tools_qmultimap.cpp 9 If you want to retrieve all the values for a single key, you can use values(const Key &key), which returns a QList: \snippet code/src_corelib_tools_qmultimap.cpp 10 The items that share the same key are available from most recently to least recently inserted. Another approach is to call find() to get the STL-style iterator for the first item with a key and iterate from there: \snippet code/src_corelib_tools_qmultimap.cpp 11 If you only need to extract the values from a map (not the keys), you can also use \l{foreach}: \snippet code/src_corelib_tools_qmultimap.cpp 12 Items can be removed from the multi map in several ways. One way is to call remove(); this will remove any item with the given key. Another way is to use QMutableMultiMapIterator::remove(). In addition, you can clear the entire map using clear(). It is possible to merge two multi maps by calling unite(), by using operator+(), and by using operator+=(). Example: \snippet code/src_corelib_tools_qmultimap.cpp 25 QMultiMap's key and value data types must be \l{assignable data types}. This covers most data types you are likely to encounter, but the compiler won't let you, for example, store a QWidget as a value; instead, store a QWidget *. In addition, QMultiMap's key type must provide operator<(). QMap uses it to keep its items sorted, and assumes that two keys \c x and \c y are equal if neither \c{x < y} nor \c{y < x} is true. Example: \snippet code/src_corelib_tools_qmultimap.cpp 13 In the example, we start by comparing the employees' names. If they're equal, we compare their dates of birth to break the tie. \sa QMultiMapIterator, QMutableMultiMapIterator, QMultiHash */ /*! \fn template QMultiMap::QMultiMap() Constructs an empty multi map. \sa clear() */ /*! \fn template QMultiMap::QMultiMap(QMultiMap &&other) Move-constructs a QMultiMap instance, making it point at the same object that \a other was pointing to. \since 5.2 */ /*! \fn template QMultiMap::QMultiMap(const QMultiMap &other) Constructs a copy of \a other. This operation occurs in \l{constant time}, because QMultiMap is \l{implicitly shared}. This makes returning a QMultiMap from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and this takes \l{linear time}. \sa operator=() */ /*! \fn template QMultiMap &QMultiMap::operator=(const QMultiMap &other) Assigns \a other to this multi map and returns a reference to this multi map. */ /*! \fn template QMultiMap &QMultiMap::operator=(QMultiMap &&other) Move-assigns \a other to this QMultiMap instance. \since 5.2 */ /*! \fn template QMultiMap::~QMultiMap() Destroys the multi map. References to the values in the multi map, and all iterators over this multi map, become invalid. */ /*! \fn template QMultiMap::QMultiMap(std::initializer_list > list) \since 5.1 Constructs a multi map with a copy of each of the elements in the initializer list \a list. */ /*! \fn template QMultiMap::QMultiMap(const QMap &other) \since 6.0 Constructs a multi map as a copy of \a other. */ /*! \fn template QMultiMap::QMultiMap(QMap &&other) \since 6.0 If \a other is shared, constructs a multi map as a copy of \a other. Otherwise, constructs a multi map by moving the elements from \a other. */ /*! \fn template QMultiMap::QMultiMap(const std::multimap &other) Constructs a copy of \a other. \sa toStdMultiMap() */ /*! \fn template QMultiMap::QMultiMap(std::multimap &&other) Constructs a multi map by moving from \a other. \sa toStdMultiMap() */ /*! \fn template std::multimap QMultiMap::toStdMap() const \deprecated Use toStdMultiMap() instead. Returns an STL multi map equivalent to this QMultiMap. */ /*! \fn template std::multimap QMultiMap::toStdMultiMap() const Returns an STL multi map equivalent to this QMultiMap. */ /*! \fn template void QMultiMap::swap(QMultiMap &other) \since 4.8 Swaps multi map \a other with this multi map. This operation is very fast and never fails. */ /*! \fn template bool QMultiMap::operator==(const QMultiMap &lhs, const QMultiMap &rhs) Returns \c true if \a lhs is equal to \a rhs; otherwise returns false. Two multi maps are considered equal if they contain the same (key, value) pairs, in the same order (which matters for duplicate keys). This function requires the key and the value types to implement \c operator==(). \sa operator!=() */ /*! \fn template bool QMultiMap::operator!=(const QMultiMap &lhs, const QMultiMap &rhs) Returns \c true if \a lhs is not equal to \a rhs; otherwise returns \c false. Two multi maps are considered equal if they contain the same (key, value) pairs, in the same order (which matters for duplicate keys). This function requires the key and the value types to implement \c operator==(). \sa operator==() */ /*! \fn template qsizetype QMultiMap::size() const Returns the number of (key, value) pairs in the multi map. \sa isEmpty(), count() */ /*! \fn template bool QMultiMap::isEmpty() const Returns \c true if the multi map contains no items; otherwise returns false. \sa size() */ /*! \fn template void QMultiMap::detach() \internal Detaches this map from any other multi maps with which it may share data. \sa isDetached() */ /*! \fn template bool QMultiMap::isDetached() const \internal Returns \c true if the multi map's internal data isn't shared with any other map object; otherwise returns \c false. \sa detach() */ /*! \fn template bool QMultiMap::isSharedWith(const QMultiMap &other) const \internal */ /*! \fn template void QMultiMap::clear() Removes all items from the multi map. \sa remove() */ /*! \fn template qsizetype QMultiMap::remove(const Key &key) Removes all the items that have the key \a key from the multi map. Returns the number of items removed. \sa clear(), take() */ /*! \fn template qsizetype QMultiMap::remove(const Key &key, const T &value) Removes all the items that have the key \a key and value \a value from the multi map. Returns the number of items removed. \sa clear(), take() */ /*! \fn template template size_type QMultiMap::removeIf(Predicate pred) \since 6.1 Removes all elements for which the predicate \a pred returns true from the multi map. The function supports predicates which take either an argument of type \c{QMultiMap::iterator}, or an argument of type \c{std::pair}. Returns the number of elements removed, if any. \sa clear(), take() */ /*! \fn template T QMultiMap::take(const Key &key) Removes the item with the key \a key from the multi map and returns the value associated with it. If the item does not exist in the multi map, the function simply returns a \l{default-constructed value}. If there are multiple items for \a key in the map, only the most recently inserted one is removed and returned. If you don't use the return value, remove() is more efficient. \sa remove() */ /*! \fn template bool QMultiMap::contains(const Key &key) const Returns \c true if the multi map contains an item with key \a key; otherwise returns \c false. \sa count() */ /*! \fn template bool QMultiMap::contains(const Key &key, const T &value) const \since 4.3 Returns \c true if the multi map contains an item with key \a key and value \a value; otherwise returns \c false. \sa count() */ /*! \fn template Key QMultiMap::key(const T &value, const Key &defaultKey) const \since 4.3 \overload Returns the first key with value \a value, or \a defaultKey if the multi map contains no item with value \a value. If no \a defaultKey is provided the function returns a \l{default-constructed value}{default-constructed key}. This function can be slow (\l{linear time}), because QMultiMap's internal data structure is optimized for fast lookup by key, not by value. \sa value(), keys() */ /*! \fn template T QMultiMap::value(const Key &key, const T &defaultValue) const Returns the value associated with the key \a key. If the multi map contains no item with key \a key, the function returns \a defaultValue. If no \a defaultValue is specified, the function returns a \l{default-constructed value}. If there are multiple items for \a key in the multi map, the value of the most recently inserted one is returned. \sa key(), values(), contains() */ /*! \fn template QList QMultiMap::keys() const Returns a list containing all the keys in the multi map in ascending order. Keys that occur multiple times in the multi map also occur multiple times in the list. The order is guaranteed to be the same as that used by values(). This function creates a new list, in \l {linear time}. The time and memory use that entails can be avoided by iterating from \l keyBegin() to \l keyEnd(). \sa values(), key() */ /*! \fn template QList QMultiMap::keys(const T &value) const \overload Returns a list containing all the keys associated with value \a value in ascending order. This function can be slow (\l{linear time}), because QMultiMap's internal data structure is optimized for fast lookup by key, not by value. */ /*! \fn template QList QMultiMap::uniqueKeys() const \since 4.2 Returns a list containing all the keys in the map in ascending order. Keys that occur multiple times in the map occur only once in the returned list. */ /*! \fn template QList QMultiMap::values() const Returns a list containing all the values in the map, in ascending order of their keys. If a key is associated with multiple values, all of its values will be in the list, and not just the most recently inserted one. \sa keys(), value() */ /*! \fn template QList QMultiMap::values(const Key &key) const Returns a list containing all the values associated with key \a key, from the most recently inserted to the least recently inserted one. \sa keys(), value() */ /*! \fn template qsizetype QMultiMap::count() const \overload Same as size(). */ /*! \fn template qsizetype QMultiMap::count(const Key &key) const Returns the number of items associated with key \a key. \sa contains(), QMultiMap::count() */ /*! \fn template qsizetype QMultiMap::count(const Key &key, const T &value) const Returns the number of items with key \a key and value \a value. \sa contains(), QMultiMap::count() */ /*! \fn template const Key &QMultiMap::firstKey() const \since 5.2 Returns a reference to the smallest key in the multi map. This function assumes that the multi map is not empty. This executes in \l{constant time}. \sa lastKey(), first(), keyBegin(), isEmpty() */ /*! \fn template const Key &QMultiMap::lastKey() const \since 5.2 Returns a reference to the largest key in the multi map. This function assumes that the multi map is not empty. This executes in \l{logarithmic time}. \sa firstKey(), last(), keyEnd(), isEmpty() */ /*! \fn template T &QMultiMap::first() \since 5.2 Returns a reference to the first value in the multi map, that is the value mapped to the smallest key. This function assumes that the multi map is not empty. When unshared (or const version is called), this executes in \l{constant time}. \sa last(), firstKey(), isEmpty() */ /*! \fn template const T &QMultiMap::first() const \since 5.2 \overload */ /*! \fn template T &QMultiMap::last() \since 5.2 Returns a reference to the last value in the multi map, that is the value mapped to the largest key. This function assumes that the map is not empty. When unshared (or const version is called), this executes in \l{logarithmic time}. \sa first(), lastKey(), isEmpty() */ /*! \fn template const T &QMultiMap::last() const \since 5.2 \overload */ /*! \fn template QMultiMap::iterator QMultiMap::begin() Returns an \l{STL-style iterators}{STL-style iterator} pointing to the first item in the multi map. \sa constBegin(), end() */ /*! \fn template QMultiMap::const_iterator QMultiMap::begin() const \overload */ /*! \fn template QMultiMap::const_iterator QMultiMap::cbegin() const \since 5.0 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item in the multi map. \sa begin(), cend() */ /*! \fn template QMultiMap::const_iterator QMultiMap::constBegin() const Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first item in the multi map. \sa begin(), constEnd() */ /*! \fn template QMultiMap::key_iterator QMultiMap::keyBegin() const \since 5.6 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first key in the multi map. \sa keyEnd(), firstKey() */ /*! \fn template QMultiMap::iterator QMultiMap::end() Returns an \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item after the last item in the multi map. \sa begin(), constEnd() */ /*! \fn template QMultiMap::const_iterator QMultiMap::end() const \overload */ /*! \fn template QMultiMap::const_iterator QMultiMap::cend() const \since 5.0 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item after the last item in the multi map. \sa cbegin(), end() */ /*! \fn template QMultiMap::const_iterator QMultiMap::constEnd() const Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item after the last item in the multi map. \sa constBegin(), end() */ /*! \fn template QMultiMap::key_iterator QMultiMap::keyEnd() const \since 5.6 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary item after the last key in the multi map. \sa keyBegin(), lastKey() */ /*! \fn template QMultiMap::key_value_iterator QMultiMap::keyValueBegin() \since 5.10 Returns an \l{STL-style iterators}{STL-style iterator} pointing to the first entry in the multi map. \sa keyValueEnd() */ /*! \fn template QMultiMap::key_value_iterator QMultiMap::keyValueEnd() \since 5.10 Returns an \l{STL-style iterators}{STL-style iterator} pointing to the imaginary entry after the last entry in the multi map. \sa keyValueBegin() */ /*! \fn template QMultiMap::const_key_value_iterator QMultiMap::keyValueBegin() const \since 5.10 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first entry in the multi map. \sa keyValueEnd() */ /*! \fn template QMultiMap::const_key_value_iterator QMultiMap::constKeyValueBegin() const \since 5.10 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first entry in the multi map. \sa keyValueBegin() */ /*! \fn template QMultiMap::const_key_value_iterator QMultiMap::keyValueEnd() const \since 5.10 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary entry after the last entry in the multi map. \sa keyValueBegin() */ /*! \fn template QMultiMap::const_key_value_iterator QMultiMap::constKeyValueEnd() const \since 5.10 Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary entry after the last entry in the multi map. \sa constKeyValueBegin() */ /*! \fn template QMultiMap::iterator QMultiMap::erase(const_iterator pos) Removes the (key, value) pair pointed to by the iterator \a pos from the multi map, and returns an iterator to the next item in the map. \note The iterator \a pos must be valid and dereferenceable. \sa remove() */ /*! \fn template QMultiMap::iterator QMultiMap::erase(const_iterator first, const_iterator last) \since 6.0 Removes the (key, value) pairs pointed to by the iterator range [\a first, \a last) from the multi map. Returns an iterator to the item in the multi map following the last removed element. \note The range \c {[first, last)} \e must be a valid range in \c {*this}. \sa remove() */ /*! \fn template QMultiMap::iterator QMultiMap::find(const Key &key) Returns an iterator pointing to the item with key \a key in the multi map. If the multi map contains no item with key \a key, the function returns end(). If the map contains multiple items with key \a key, this function returns an iterator that points to the most recently inserted value. The other values are accessible by incrementing the iterator. For example, here's some code that iterates over all the items with the same key: \snippet code/src_corelib_tools_qmultimap.cpp 11 \sa constFind(), value(), values(), lowerBound(), upperBound() */ /*! \fn template QMultiMap::const_iterator QMultiMap::find(const Key &key) const \overload */ /*! \fn template QMultiMap::const_iterator QMultiMap::constFind(const Key &key) const \since 4.1 Returns an const iterator pointing to the item with key \a key in the multi map. If the multi map contains no item with key \a key, the function returns constEnd(). \sa find(), QMultiMap::constFind() */ /*! \fn template typename QMultiMap::const_iterator QMultiMap::find(const Key &key, const T &value) const \since 4.3 \overload Returns a const iterator pointing to the item with the given \a key and \a value in the map. If the map contains no such item, the function returns end(). If the map contains multiple items with the specified \a key, this function returns a const iterator that points to the most recently inserted value. */ /*! \fn template typename QMultiMap::const_iterator QMultiMap::constFind(const Key &key, const T &value) const \since 4.3 Returns an iterator pointing to the item with key \a key and the value \a value in the map. If the map contains no such item, the function returns constEnd(). \sa QMap::constFind() */ /*! \fn template QMultiMap::iterator QMultiMap::lowerBound(const Key &key) Returns an iterator pointing to the first item with key \a key in the map. If the map contains no item with key \a key, the function returns an iterator to the nearest item with a greater key. Example: \snippet code/src_corelib_tools_qmultimap.cpp 15 If the map contains multiple items with key \a key, this function returns an iterator that points to the most recently inserted value. The other values are accessible by incrementing the iterator. For example, here's some code that iterates over all the items with the same key: \snippet code/src_corelib_tools_qmultimap.cpp 16 \sa upperBound(), find() */ /*! \fn template QMultiMap::const_iterator QMultiMap::lowerBound(const Key &key) const \overload */ /*! \fn template QMultiMap::iterator QMultiMap::upperBound(const Key &key) Returns an iterator pointing to the item that immediately follows the last item with key \a key in the map. If the map contains no item with key \a key, the function returns an iterator to the nearest item with a greater key. Example: \snippet code/src_corelib_tools_qmultimap.cpp 17 \sa lowerBound(), find() */ /*! \fn template QMultiMap::const_iterator QMultiMap::upperBound(const Key &key) const \overload */ /*! \fn template QMultiMap::iterator QMultiMap::insert(const Key &key, const T &value) Inserts a new item with the key \a key and a value of \a value. If there is already an item with the same key in the map, this function will simply create a new one. (This behavior is different from replace(), which overwrites the value of an existing item.) \sa replace() */ /*! \fn template QMultiMap::iterator QMultiMap::insert(const_iterator pos, const Key &key, const T &value) \overload \since 5.1 Inserts a new item with the key \a key and value \a value and with hint \a pos suggesting where to do the insert. If constBegin() is used as hint it indicates that the \a key is less than any key in the multi map while constEnd() suggests that the \a key is (strictly) larger than any key in the multi map. Otherwise the hint should meet the condition (\a pos - 1).key() < \a key <= pos.key(). If the hint \a pos is wrong it is ignored and a regular insert is done. If the hint is correct and the multi map is unshared, the insert executes in amortized \l{constant time}. If there is already an item with the same key in the map, this function will simply create a new one. When creating a multi map from sorted data inserting the largest key first with constBegin() is faster than inserting in sorted order with constEnd(), since constEnd() - 1 (which is needed to check if the hint is valid) needs \l{logarithmic time}. \b {Note:} Be careful with the hint. Providing an iterator from an older shared instance might crash but there is also a risk that it will silently corrupt both the multi map and the \a pos multi map. */ #if QT_DEPRECATED_SINCE(6, 0) /*! \fn template QMultiMap::iterator QMultiMap::insertMulti(const Key &key, const T &value) \deprecated Use insert() instead. Inserts a new item with the key \a key and a value of \a value, and returns an iterator pointing to the new item. */ /*! \fn template QMultiMap::iterator QMultiMap::insertMulti(const_iterator pos, const Key &key, const T &value) \deprecated Use insert() instead. \overload Inserts a new item with the key \a key and value \a value and with hint \a pos suggesting where to do the insert. */ /*! \fn template void QMultiMap::insert(const QMultiMap &map) \since 5.15 \deprecated Use unite() instead. Inserts all the items in \a map into this map. */ /*! \fn template void QMultiMap::insert(QMultiMap &&map) \since 5.15 \deprecated Use unite() instead. \overload Moves all the items from \a map into this map. If \a map is shared, then the items will be copied instead. */ #endif /*! \fn template QMultiMap::iterator QMultiMap::replace(const Key &key, const T &value) Inserts a new item with the key \a key and a value of \a value. If there is already an item with the key \a key, that item's value is replaced with \a value. If there are multiple items with the key \a key, the most recently inserted item's value is replaced with \a value. \sa insert() */ /*! \typedef QMultiMap::Iterator Qt-style synonym for QMultiMap::iterator. */ /*! \typedef QMultiMap::ConstIterator Qt-style synonym for QMultiMap::const_iterator. */ /*! \typedef QMultiMap::difference_type Typedef for ptrdiff_t. Provided for STL compatibility. */ /*! \typedef QMultiMap::key_type Typedef for Key. Provided for STL compatibility. */ /*! \typedef QMultiMap::mapped_type Typedef for T. Provided for STL compatibility. */ /*! \typedef QMultiMap::size_type Typedef for int. Provided for STL compatibility. */ /*! \fn template bool QMultiMap::empty() const This function is provided for STL compatibility. It is equivalent to isEmpty(), returning true if the map is empty; otherwise returning false. */ /*! \fn template QPair::iterator, typename QMultiMap::iterator> QMultiMap::equal_range(const Key &key) Returns a pair of iterators delimiting the range of values \c{[first, second)}, that are stored under \a key. */ /*! \fn template QPair::const_iterator, typename QMultiMap::const_iterator> QMultiMap::equal_range(const Key &key) const \overload \since 5.6 */ /*! \fn template QMultiMap &QMultiMap::unite(const QMultiMap &other) Inserts all the items in the \a other map into this map. If a key is common to both maps, the resulting map will contain the key multiple times. */ /*! \fn template QMultiMap &QMultiMap::unite(QMultiMap &&other) Moves all the items from the \a other map into this map. If a key is common to both maps, the resulting map will contain the key multiple times. If \a other is shared, then the items will be copied instead. */ /*! \fn template QMultiMap operator+=(QMultiMap &lhs, const QMultiMap &rhs) Inserts all the items in the \a rhs map into the \a lhs map and returns the resulting map. \sa insert(), operator+() */ /*! \fn template QMultiMap operator+(const QMultiMap &lhs, const QMultiMap &rhs) Returns a map that contains all the items in the \a lhs map in addition to all the items in \a rhs. If a key is common to both maps, the resulting map will contain the key multiple times. \sa operator+=() */ /*! \class QMultiMap::iterator \inmodule QtCore \brief The QMultiMap::iterator class provides an STL-style non-const iterator for QMultiMap. QMultiMap features both \l{STL-style iterators} and \l{Java-style iterators}. The STL-style iterators are more low-level and more cumbersome to use; on the other hand, they are slightly faster and, for developers who already know STL, have the advantage of familiarity. QMultiMap\::iterator allows you to iterate over a QMultiMap and to modify the value (but not the key) stored under a particular key. If you want to iterate over a const QMultiMap, you should use QMultiMap::const_iterator. It is generally good practice to use QMultiMap::const_iterator on a non-const QMultiMap as well, unless you need to change the QMultiMap through the iterator. Const iterators are slightly faster, and can improve code readability. The default QMultiMap::iterator constructor creates an uninitialized iterator. You must initialize it using a QMultiMap function like QMultiMap::begin(), QMultiMap::end(), or QMultiMap::find() before you can start iterating. Here's a typical loop that prints all the (key, value) pairs stored in a map: \snippet code/src_corelib_tools_qmultimap.cpp 18 Unlike QMultiHash, which stores its items in an arbitrary order, QMultiMap stores its items ordered by key. Items that share the same key will appear consecutively, from the most recently to the least recently inserted value. Let's see a few examples of things we can do with a QMultiMap::iterator that we cannot do with a QMultiMap::const_iterator. Here's an example that increments every value stored in the QMultiMap by 2: \snippet code/src_corelib_tools_qmultimap.cpp 19 Here's an example that removes all the items whose key is a string that starts with an underscore character: \snippet code/src_corelib_tools_qmultimap.cpp 20 The call to QMultiMap::erase() removes the item pointed to by the iterator from the map, and returns an iterator to the next item. Here's another way of removing an item while iterating: \snippet code/src_corelib_tools_qmultimap.cpp 21 It might be tempting to write code like this: \snippet code/src_corelib_tools_qmultimap.cpp 22 However, this will potentially crash in \c{++i}, because \c i is a dangling iterator after the call to erase(). Multiple iterators can be used on the same map. If you add items to the map, existing iterators will remain valid. If you remove items from the map, iterators that point to the removed items will become dangling iterators. \warning Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read \l{Implicit sharing iterator problem}. \sa QMultiMap::const_iterator, QMultiMap::key_iterator, QMutableMultiMapIterator */ /*! \typedef QMultiMap::iterator::difference_type \internal */ /*! \typedef QMultiMap::iterator::iterator_category A synonym for \e {std::bidirectional_iterator_tag} indicating this iterator is a bidirectional iterator. */ /*! \typedef QMultiMap::iterator::pointer \internal */ /*! \typedef QMultiMap::iterator::reference \internal */ /*! \typedef QMultiMap::iterator::value_type \internal */ /*! \fn template QMultiMap::iterator::iterator() Constructs an uninitialized iterator. Functions like key(), value(), and operator++() must not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it. \sa QMultiMap::begin(), QMultiMap::end() */ /*! \fn template const Key &QMultiMap::iterator::key() const Returns the current item's key as a const reference. There is no direct way of changing an item's key through an iterator, although it can be done by calling QMultiMap::erase() followed by QMultiMap::insert(). \sa value() */ /*! \fn template T &QMultiMap::iterator::value() const Returns a modifiable reference to the current item's value. You can change the value of an item by using value() on the left side of an assignment, for example: \snippet code/src_corelib_tools_qmultimap.cpp 23 \sa key(), operator*() */ /*! \fn template T &QMultiMap::iterator::operator*() const Returns a modifiable reference to the current item's value. Same as value(). \sa key() */ /*! \fn template T *QMultiMap::iterator::operator->() const Returns a pointer to the current item's value. \sa value() */ /*! \fn template bool QMultiMap::iterator::operator==(const iterator &lhs, const iterator &rhs) \fn template bool QMultiMap::const_iterator::operator==(const const_iterator &lhs, const const_iterator &rhs) Returns \c true if \a lhs points to the same item as the \a rhs iterator; otherwise returns \c false. \sa operator!=() */ /*! \fn template bool QMultiMap::iterator::operator!=(const iterator &lhs, const iterator &rhs) \fn template bool QMultiMap::const_iterator::operator!=(const const_iterator &lhs, const const_iterator &rhs) Returns \c true if \a lhs points to a different item than the \a rhs iterator; otherwise returns \c false. \sa operator==() */ /*! \fn template QMultiMap::iterator &QMultiMap::iterator::operator++() The prefix ++ operator (\c{++i}) advances the iterator to the next item in the multi map and returns an iterator to the new current item. Calling this function on QMultiMap::end() leads to undefined results. \sa operator--() */ /*! \fn template QMultiMap::iterator QMultiMap::iterator::operator++(int) \overload The postfix ++ operator (\c{i++}) advances the iterator to the next item in the multi map and returns an iterator to the previously current item. */ /*! \fn template QMultiMap::iterator &QMultiMap::iterator::operator--() The prefix -- operator (\c{--i}) makes the preceding item current and returns an iterator pointing to the new current item. Calling this function on QMultiMap::begin() leads to undefined results. \sa operator++() */ /*! \fn template QMultiMap::iterator QMultiMap::iterator::operator--(int) \overload The postfix -- operator (\c{i--}) makes the preceding item current and returns an iterator pointing to the previously current item. */ /*! //! friends \fn [qmultimap-op-it-plus-step] template typename QMultiMap::iterator QMultiMap::iterator::operator+(QMultiMap::iterator, difference_type n) \fn [qmultimap-op-step-plus-it] template QMultiMap::iterator QMultiMap::iterator::operator+(difference_type n, QMultiMap::iterator) \fn [qmultimap-op-it-minus-step] template QMultiMap::iterator QMultiMap::iterator::operator-(QMultiMap::iterator, difference_type n) \fn [qmultimap-op-step-minus-it] template QMultiMap::iterator QMultiMap::iterator::operator-(difference_type n, QMultiMap::iterator) //! members \fn template typename QMultiMap::iterator QMultiMap::iterator::operator+=(QMultiMap::iterator::difference_type n) \fn template typename QMultiMap::iterator QMultiMap::iterator::operator-=(QMultiMap::iterator::difference_type n) \deprecated [6.2] Use \c{std::next}, \c{std::prev} or \c{std::advance} instead. Move an iterator by \e{n} positions. These operations can be expensive for large values of \e{n}; QMultiMap iterators are not random access. */ /*! \class QMultiMap::const_iterator \inmodule QtCore \brief The QMultiMap::const_iterator class provides an STL-style const iterator for QMultiMap. QMultiMap features both \l{STL-style iterators} and \l{Java-style iterators}. The STL-style iterators are more low-level and more cumbersome to use; on the other hand, they are slightly faster and, for developers who already know STL, have the advantage of familiarity. QMultiMap\::const_iterator allows you to iterate over a QMultiMap. If you want to modify the QMultiMap as you iterate over it, you must use QMultiMap::iterator instead. It is generally good practice to use QMultiMap::const_iterator on a non-const QMultiMap as well, unless you need to change the QMultiMap through the iterator. Const iterators are slightly faster, and can improve code readability. The default QMultiMap::const_iterator constructor creates an uninitialized iterator. You must initialize it using a QMultiMap function like QMultiMap::constBegin(), QMultiMap::constEnd(), or QMultiMap::find() before you can start iterating. Here's a typical loop that prints all the (key, value) pairs stored in a map: \snippet code/src_corelib_tools_qmultimap.cpp 24 Unlike QMultiHash, which stores its items in an arbitrary order, QMultiMap stores its items ordered by key. Items that share the same key will appear consecutively, from the most recently to the least recently inserted value. Multiple iterators can be used on the same multi map. If you add items to the map, existing iterators will remain valid. If you remove items from the map, iterators that point to the removed items will become dangling iterators. \warning Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read \l{Implicit sharing iterator problem}. \sa QMultiMap::iterator, QMultiMap::key_iterator, QMultiMapIterator */ /*! \typedef QMultiMap::const_iterator::difference_type \internal */ /*! \typedef QMultiMap::const_iterator::iterator_category A synonym for \e {std::bidirectional_iterator_tag} indicating this iterator is a bidirectional iterator. */ /*! \typedef QMultiMap::const_iterator::pointer \internal */ /*! \typedef QMultiMap::const_iterator::reference \internal */ /*! \typedef QMultiMap::const_iterator::value_type \internal */ /*! \fn template QMultiMap::const_iterator::const_iterator() Constructs an uninitialized iterator. Functions like key(), value(), and operator++() must not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it. \sa QMultiMap::constBegin(), QMultiMap::constEnd() */ /*! \fn template QMultiMap::const_iterator::const_iterator(const iterator &other) Constructs a copy of \a other. */ /*! \fn template const Key &QMultiMap::const_iterator::key() const Returns the current item's key. \sa value() */ /*! \fn template const T &QMultiMap::const_iterator::value() const Returns the current item's value. \sa key(), operator*() */ /*! \fn template const T &QMultiMap::const_iterator::operator*() const Returns the current item's value. Same as value(). \sa key() */ /*! \fn template const T *QMultiMap::const_iterator::operator->() const Returns a pointer to the current item's value. \sa value() */ /*! \fn template QMultiMap::const_iterator &QMultiMap::const_iterator::operator++() The prefix ++ operator (\c{++i}) advances the iterator to the next item in the map and returns an iterator to the new current item. Calling this function on QMultiMap::end() leads to undefined results. \sa operator--() */ /*! \fn template QMultiMap::const_iterator QMultiMap::const_iterator::operator++(int) \overload The postfix ++ operator (\c{i++}) advances the iterator to the next item in the map and returns an iterator to the previously current item. */ /*! \fn template QMultiMap::const_iterator &QMultiMap::const_iterator::operator--() The prefix -- operator (\c{--i}) makes the preceding item current and returns an iterator pointing to the new current item. Calling this function on QMultiMap::begin() leads to undefined results. \sa operator++() */ /*! \fn template QMultiMap::const_iterator QMultiMap::const_iterator::operator--(int) \overload The postfix -- operator (\c{i--}) makes the preceding item current and returns an iterator pointing to the previously current item. */ /*! //! friends \fn [qmultimap-op-it-plus-step-const] template typename QMultiMap::const_iterator QMultiMap::const_iterator::operator+(QMultiMap::const_iterator, difference_type n) \fn [qmultimap-op-step-plus-it-const] template QMultiMap::const_iterator QMultiMap::const_iterator::operator+(difference_type n, QMultiMap::const_iterator) \fn [qmultimap-op-it-minus-step-const] template QMultiMap::const_iterator QMultiMap::const_iterator::operator-(QMultiMap::const_iterator, difference_type n) \fn [qmultimap-op-step-minus-it-const] template QMultiMap::const_iterator QMultiMap::const_iterator::operator-(difference_type n, QMultiMap::const_iterator) //! members \fn template typename QMultiMap::const_iterator QMultiMap::const_iterator::operator+=(QMultiMap::const_iterator::difference_type n) \fn template typename QMultiMap::const_iterator QMultiMap::const_iterator::operator-=(QMultiMap::const_iterator::difference_type n) \deprecated [6.2] Use \c{std::next}, \c{std::prev} or \c{std::advance} instead. Move an iterator by \e{n} positions. These operations can be expensive for large values of \e{n}. QMultiMap iterators are not random access. */ /*! \class QMultiMap::key_iterator \inmodule QtCore \since 5.6 \brief The QMultiMap::key_iterator class provides an STL-style const iterator for QMultiMap keys. QMultiMap::key_iterator is essentially the same as QMultiMap::const_iterator with the difference that operator*() and operator->() return a key instead of a value. For most uses QMultiMap::iterator and QMultiMap::const_iterator should be used, you can easily access the key by calling QMultiMap::iterator::key(): \snippet code/src_corelib_tools_qmultimap.cpp keyiterator1 However, to have interoperability between QMultiMap's keys and STL-style algorithms we need an iterator that dereferences to a key instead of a value. With QMultiMap::key_iterator we can apply an algorithm to a range of keys without having to call QMultiMap::keys(), which is inefficient as it costs one QMultiMap iteration and memory allocation to create a temporary QList. \snippet code/src_corelib_tools_qmultimap.cpp keyiterator2 QMultiMap::key_iterator is const, it's not possible to modify the key. The default QMultiMap::key_iterator constructor creates an uninitialized iterator. You must initialize it using a QMultiMap function like QMultiMap::keyBegin() or QMultiMap::keyEnd(). \warning Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read \l{Implicit sharing iterator problem}. \sa QMultiMap::const_iterator, QMultiMap::iterator */ /*! \typedef QMultiMap::key_iterator::difference_type \internal */ /*! \typedef QMultiMap::key_iterator::iterator_category \internal */ /*! \typedef QMultiMap::key_iterator::pointer \internal */ /*! \typedef QMultiMap::key_iterator::reference \internal */ /*! \typedef QMultiMap::key_iterator::value_type \internal */ /*! \fn template const T &QMultiMap::key_iterator::operator*() const Returns the current item's key. */ /*! \fn template const T *QMultiMap::key_iterator::operator->() const Returns a pointer to the current item's key. */ /*! \fn template bool QMultiMap::key_iterator::operator==(key_iterator other) const Returns \c true if \a other points to the same item as this iterator; otherwise returns \c false. \sa operator!=() */ /*! \fn template bool QMultiMap::key_iterator::operator!=(key_iterator other) const Returns \c true if \a other points to a different item than this iterator; otherwise returns \c false. \sa operator==() */ /*! \fn template QMultiMap::key_iterator &QMultiMap::key_iterator::operator++() The prefix ++ operator (\c{++i}) advances the iterator to the next item in the hash and returns an iterator to the new current item. Calling this function on QMultiMap::keyEnd() leads to undefined results. \sa operator--() */ /*! \fn template QMultiMap::key_iterator QMultiMap::key_iterator::operator++(int) \overload The postfix ++ operator (\c{i++}) advances the iterator to the next item in the hash and returns an iterator to the previous item. */ /*! \fn template QMultiMap::key_iterator &QMultiMap::key_iterator::operator--() The prefix -- operator (\c{--i}) makes the preceding item current and returns an iterator pointing to the new current item. Calling this function on QMultiMap::keyBegin() leads to undefined results. \sa operator++() */ /*! \fn template QMultiMap::key_iterator QMultiMap::key_iterator::operator--(int) \overload The postfix -- operator (\c{i--}) makes the preceding item current and returns an iterator pointing to the previous item. */ /*! \fn template const_iterator QMultiMap::key_iterator::base() const Returns the underlying const_iterator this key_iterator is based on. */ /*! \typedef QMultiMap::const_key_value_iterator \inmodule QtCore \since 5.10 \brief The QMultiMap::const_key_value_iterator typedef provides an STL-style iterator for QMultiMap. QMultiMap::const_key_value_iterator is essentially the same as QMultiMap::const_iterator with the difference that operator*() returns a key/value pair instead of a value. \sa QKeyValueIterator */ /*! \typedef QMultiMap::key_value_iterator \inmodule QtCore \since 5.10 \brief The QMultiMap::key_value_iterator typedef provides an STL-style iterator for QMultiMap. QMultiMap::key_value_iterator is essentially the same as QMultiMap::iterator with the difference that operator*() returns a key/value pair instead of a value. \sa QKeyValueIterator */ /*! \fn template QDataStream &operator<<(QDataStream &out, const QMultiMap &map) \relates QMultiMap Writes the multi map \a map to stream \a out. This function requires the key and value types to implement \c operator<<(). \sa{Serializing Qt Data Types}{Format of the QDataStream operators} */ /*! \fn template QDataStream &operator>>(QDataStream &in, QMultiMap &map) \relates QMultiMap Reads a map from stream \a in into \a map. This function requires the key and value types to implement \c operator>>(). \sa{Serializing Qt Data Types}{Format of the QDataStream operators} */ /*! \fn template qsizetype erase_if(QMultiMap &map, Predicate pred) \relates QMultiMap \since 6.1 Removes all elements for which the predicate \a pred returns true from the multi map \a map. The function supports predicates which take either an argument of type \c{QMultiMap::iterator}, or an argument of type \c{std::pair}. Returns the number of elements removed, if any. */