diff options
Diffstat (limited to 'src/corelib/tools/qmap.qdoc')
| -rw-r--r-- | src/corelib/tools/qmap.qdoc | 137 |
1 files changed, 57 insertions, 80 deletions
diff --git a/src/corelib/tools/qmap.qdoc b/src/corelib/tools/qmap.qdoc index 5d0825708b..0cabf3df38 100644 --- a/src/corelib/tools/qmap.qdoc +++ b/src/corelib/tools/qmap.qdoc @@ -1,6 +1,6 @@ // Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> // Copyright (C) 2016 The Qt Company Ltd. -// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only +// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only /*! \class QMap @@ -87,27 +87,17 @@ The items are traversed in ascending key order. - Normally, a QMap allows only one value per key. If you call + A QMap allows only one value per key. If you call insert() with a key that already exists in the QMap, the previous value will be erased. For example: \snippet code/src_corelib_tools_qmap.cpp 9 However, you can store multiple values per key by using - QMultiMap. If you want - to retrieve all the values for a single key, you can use - values(const Key &key), which returns a QList<T>: - - \snippet code/src_corelib_tools_qmap.cpp 10 - - 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_qmap.cpp 11 + QMultiMap. If you only need to extract the values from a map (not the keys), - you can also use \l{foreach}: + you can also use range-based for: \snippet code/src_corelib_tools_qmap.cpp 12 @@ -212,6 +202,15 @@ Returns an STL map equivalent to this QMap. */ +/*! \fn template <class Key, class T> std::map<Key, T> QMap<Key, T>::toStdMap() && + + \overload + \since 6.0 + + \note Calling this function will leave this QMap in the partially-formed state, in which + the only valid operations are destruction or assignment of a new value. +*/ + /*! \fn template <class Key, class T> bool QMap<Key, T>::operator==(const QMap<Key, T> &lhs, const QMap<Key, T> &rhs) Returns \c true if \a lhs is equal to \a rhs; otherwise returns @@ -318,9 +317,7 @@ the value associated with it. If the item does not exist in the 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. + returns a \l{default-constructed value}. If you don't use the return value, remove() is more efficient. @@ -370,9 +367,7 @@ If the map contains no item with key \a key, the function inserts a \l{default-constructed value} into the map with key \a key, and - returns a reference to it. If the map contains multiple items - with key \a key, this function returns a reference to the most - recently inserted value. + returns a reference to it. \sa insert(), value() */ @@ -395,7 +390,7 @@ use that entails can be avoided by iterating from \l keyBegin() to \l keyEnd(). - \sa QMultiMap::uniqueKeys(), values(), key() + \sa values(), key() */ /*! \fn template <class Key, class T> QList<Key> QMap<Key, T>::keys(const T &value) const @@ -413,9 +408,7 @@ /*! \fn template <class Key, class T> QList<T> QMap<Key, T>::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. + order of their keys. This function creates a new list, in \l {linear time}. The time and memory use that entails can be avoided by iterating from \l keyValueBegin() to @@ -737,7 +730,7 @@ If there is already an item with the key \a key, that item's value is replaced with \a value. - \sa QMultiMap::insert() + Returns an iterator pointing to the new/updated element. */ /*! \fn template <class Key, class T> QMap<Key, T>::iterator QMap<Key, T>::insert(const_iterator pos, const Key &key, const T &value) @@ -763,7 +756,7 @@ \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 map and the \a pos map. - \sa QMultiMap::insert() + Returns an iterator pointing to the new/updated element. */ /*! \fn template <class Key, class T> void QMap<Key, T>::insert(const QMap<Key, T> &map) @@ -773,11 +766,6 @@ If a key is common to both maps, its value will be replaced with the value stored in \a map. - - \note If \a map contains multiple entries with the same key then the - final value of the key is undefined. - - \sa QMultiMap::insert() */ /*! \fn template <class Key, class T> void QMap<Key, T>::insert(QMap<Key, T> &&map) @@ -793,12 +781,12 @@ /*! \typedef QMap::Iterator - Qt-style synonym for QMap<Key, T>::iterator. + Qt-style synonym for QMap::iterator. */ /*! \typedef QMap::ConstIterator - Qt-style synonym for QMap<Key, T>::const_iterator. + Qt-style synonym for QMap::const_iterator. */ /*! \typedef QMap::difference_type @@ -830,14 +818,14 @@ */ /*! - \fn template <class Key, class T> QPair<typename QMap<Key, T>::iterator, typename QMap<Key, T>::iterator> QMap<Key, T>::equal_range(const Key &key) + \fn template <class Key, class T> std::pair<typename QMap<Key, T>::iterator, typename QMap<Key, T>::iterator> QMap<Key, T>::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 <class Key, class T> QPair<typename QMap<Key, T>::const_iterator, typename QMap<Key, T>::const_iterator> QMap<Key, T>::equal_range(const Key &key) const + \fn template <class Key, class T> std::pair<typename QMap<Key, T>::const_iterator, typename QMap<Key, T>::const_iterator> QMap<Key, T>::equal_range(const Key &key) const \overload \since 5.6 */ @@ -847,12 +835,6 @@ \inmodule QtCore \brief The QMap::iterator class provides an STL-style non-const iterator for QMap. - QMap 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. - QMap\<Key, T\>::iterator allows you to iterate over a QMap and to modify the value (but not the key) stored under a particular key. If you want to iterate over a const QMap, you @@ -872,31 +854,15 @@ Unlike QHash, which stores its items in an arbitrary order, QMap stores its items ordered by key. - Let's see a few examples of things we can do with a - QMap::iterator that we cannot do with a QMap::const_iterator. Here's an example that increments every value stored in the QMap by 2: \snippet code/src_corelib_tools_qmap.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_qmap.cpp 20 - - The call to QMap::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: + To remove elements from a QMap you can use erase_if(QMap\<Key, T\> &map, Predicate pred): \snippet code/src_corelib_tools_qmap.cpp 21 - It might be tempting to write code like this: - - \snippet code/src_corelib_tools_qmap.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 @@ -907,7 +873,7 @@ while iterators are active on that container. For more information, read \l{Implicit sharing iterator problem}. - \sa QMap::const_iterator, QMap::key_iterator, QMutableMapIterator + \sa QMap::const_iterator, QMap::key_iterator, QMap::key_value_iterator */ /*! \typedef QMap::iterator::difference_type @@ -1008,7 +974,7 @@ /*! \fn template <class Key, class T> QMap<Key, T>::iterator &QMap<Key, T>::iterator::operator++() - The prefix ++ operator (\c{++i}) advances the iterator to the + The prefix \c{++} operator (\c{++i}) advances the iterator to the next item in the map and returns an iterator to the new current item. @@ -1021,14 +987,14 @@ \overload - The postfix ++ operator (\c{i++}) advances the iterator to the + The postfix \c{++} operator (\c{i++}) advances the iterator to the next item in the map and returns an iterator to the previously current item. */ /*! \fn template <class Key, class T> QMap<Key, T>::iterator &QMap<Key, T>::iterator::operator--() - The prefix -- operator (\c{--i}) makes the preceding item + The prefix \c{--} operator (\c{--i}) makes the preceding item current and returns an iterator pointing to the new current item. Calling this function on QMap::begin() leads to undefined @@ -1041,7 +1007,7 @@ \overload - The postfix -- operator (\c{i--}) makes the preceding item + The postfix \c{--} operator (\c{i--}) makes the preceding item current and returns an iterator pointing to the previously current item. */ @@ -1067,12 +1033,6 @@ \inmodule QtCore \brief The QMap::const_iterator class provides an STL-style const iterator for QMap. - QMap 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. - QMap\<Key, T\>::const_iterator allows you to iterate over a QMap. If you want to modify the QMap as you iterate over it, you must use QMap::iterator instead. It is generally @@ -1083,12 +1043,20 @@ The default QMap::const_iterator constructor creates an uninitialized iterator. You must initialize it using a QMap - function like QMap::constBegin(), QMap::constEnd(), or - QMap::find() before you can start iterating. Here's a typical + function like QMap::cbegin(), QMap::cend(), or + QMap::constFind() 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_qmap.cpp 24 + Here's an example that removes all the items whose value is greater than 10: + + \snippet code/src_corelib_tools_qmap.cpp 20 + + And here the same behavior with erase_if() + + \snippet code/src_corelib_tools_qmap.cpp 21 + Unlike QHash, which stores its items in an arbitrary order, QMap stores its items ordered by key. @@ -1102,7 +1070,7 @@ while iterators are active on that container. For more information, read \l{Implicit sharing iterator problem}. - \sa QMap::iterator, QMap::key_iterator, QMapIterator + \sa QMap::iterator, QMap::key_iterator, QMap::const_key_value_iterator */ /*! \typedef QMap::const_iterator::difference_type @@ -1179,7 +1147,7 @@ /*! \fn template <class Key, class T> QMap<Key, T>::const_iterator &QMap<Key, T>::const_iterator::operator++() - The prefix ++ operator (\c{++i}) advances the iterator to the + The prefix \c{++} operator (\c{++i}) advances the iterator to the next item in the map and returns an iterator to the new current item. @@ -1192,14 +1160,14 @@ \overload - The postfix ++ operator (\c{i++}) advances the iterator to the + The postfix \c{++} operator (\c{i++}) advances the iterator to the next item in the map and returns an iterator to the previously current item. */ /*! \fn template <class Key, class T> QMap<Key, T>::const_iterator &QMap<Key, T>::const_iterator::operator--() - The prefix -- operator (\c{--i}) makes the preceding item + The prefix \c{--} operator (\c{--i}) makes the preceding item current and returns an iterator pointing to the new current item. Calling this function on QMap::begin() leads to undefined @@ -1212,7 +1180,7 @@ \overload - The postfix -- operator (\c{i--}) makes the preceding item + The postfix \c{--} operator (\c{i--}) makes the preceding item current and returns an iterator pointing to the previously current item. */ @@ -1320,7 +1288,7 @@ /*! \fn template <class Key, class T> QMap<Key, T>::key_iterator &QMap<Key, T>::key_iterator::operator++() - The prefix ++ operator (\c{++i}) advances the iterator to the + The prefix \c{++} operator (\c{++i}) advances the iterator to the next item in the hash and returns an iterator to the new current item. @@ -1333,14 +1301,14 @@ \overload - The postfix ++ operator (\c{i++}) advances the iterator to the + The postfix \c{++} operator (\c{i++}) advances the iterator to the next item in the hash and returns an iterator to the previous item. */ /*! \fn template <class Key, class T> QMap<Key, T>::key_iterator &QMap<Key, T>::key_iterator::operator--() - The prefix -- operator (\c{--i}) makes the preceding item + The prefix \c{--} operator (\c{--i}) makes the preceding item current and returns an iterator pointing to the new current item. Calling this function on QMap::keyBegin() leads to undefined @@ -1353,7 +1321,7 @@ \overload - The postfix -- operator (\c{i--}) makes the preceding item + The postfix \c{--} operator (\c{i--}) makes the preceding item current and returns an iterator pointing to the previous item. */ @@ -1421,3 +1389,12 @@ Returns the number of elements removed, if any. */ + +/*! + \fn template <class Key, class T> size_t QMap<Key, T>::qHash(const QMap &key, size_t seed) noexcept + \since 6.8 + + Returns the hash value for \a key, using \a seed to seed the calculation. + + Types \c Key and \c T must be supported by qHash(). +*/ |