The QMultiMap class is a template class that provides an associative array with multiple equivalent keys. 更多...
| 頭： | #include <QMultiMap> |
| CMake: |
find_package(Qt6 REQUIRED COMPONENTS Core)
target_link_libraries(mytarget PRIVATE Qt6::Core) |
| qmake: | QT += core |
注意： 此類的所有函數 可重入 .
| class | const_iterator |
| class | iterator |
| class | key_iterator |
| ConstIterator | |
| Iterator | |
| const_key_value_iterator | |
| difference_type | |
| key_type | |
| key_value_iterator | |
| mapped_type | |
| size_type |
| QMultiMap () | |
| QMultiMap (std::initializer_list<std::pair<Key, T>> list ) | |
| QMultiMap (const QMap<Key, T> & other ) | |
| QMultiMap (QMap<Key, T> && other ) | |
| QMultiMap (const std::multimap<Key, T> & other ) | |
| QMultiMap (std::multimap<Key, T> && other ) | |
| QMultiMap (QMultiMap<Key, T> && other ) | |
| QMultiMap (const QMultiMap<Key, T> & other ) | |
| ~QMultiMap () | |
| auto | asKeyValueRange () & |
| auto | asKeyValueRange () const & |
| auto | asKeyValueRange () && |
| auto | asKeyValueRange () const && |
| QMultiMap::iterator | begin () |
| QMultiMap::const_iterator | begin () const |
| QMultiMap::const_iterator | cbegin () const |
| QMultiMap::const_iterator | cend () const |
| void | clear () |
| QMultiMap::const_iterator | constBegin () const |
| QMultiMap::const_iterator | constEnd () const |
| QMultiMap::const_iterator | constFind (const Key & key ) const |
| QMultiMap::const_iterator | constFind (const Key & key , const T & value ) const |
| QMultiMap::const_key_value_iterator | constKeyValueBegin () const |
| QMultiMap::const_key_value_iterator | constKeyValueEnd () const |
| bool | contains (const Key & key ) const |
| bool | contains (const Key & key , const T & value ) const |
| QMultiMap::size_type | count (const Key & key ) const |
| QMultiMap::size_type | count (const Key & key , const T & value ) const |
| QMultiMap::size_type | count () const |
| bool | empty () const |
| QMultiMap::iterator | end () |
| QMultiMap::const_iterator | end () const |
| QPair<QMultiMap::iterator, QMultiMap::iterator> | equal_range (const Key & key ) |
| QPair<QMultiMap::const_iterator, QMultiMap::const_iterator> | equal_range (const Key & key ) const |
| QMultiMap::iterator | erase (QMultiMap::const_iterator pos ) |
| QMultiMap::iterator | erase (QMultiMap::const_iterator first , QMultiMap::const_iterator last ) |
| QMultiMap::iterator | find (const Key & key ) |
| QMultiMap::const_iterator | find (const Key & key ) const |
| QMultiMap::const_iterator | find (const Key & key , const T & value ) const |
| T & | first () |
| const T & | first () const |
| const Key & | firstKey () const |
| QMultiMap::iterator | insert (const Key & key , const T & value ) |
| QMultiMap::iterator | insert (QMultiMap::const_iterator pos , const Key & key , const T & value ) |
| bool | isEmpty () const |
| Key | key (const T & value , const Key & defaultKey = Key()) const |
| QMultiMap::key_iterator | keyBegin () const |
| QMultiMap::key_iterator | keyEnd () const |
| QMultiMap::key_value_iterator | keyValueBegin () |
| QMultiMap::const_key_value_iterator | keyValueBegin () const |
| QMultiMap::key_value_iterator | keyValueEnd () |
| QMultiMap::const_key_value_iterator | keyValueEnd () const |
| QList<Key> | keys () const |
| QList<Key> | keys (const T & value ) const |
| T & | last () |
| const T & | last () const |
| const Key & | lastKey () const |
| QMultiMap::iterator | lowerBound (const Key & key ) |
| QMultiMap::const_iterator | lowerBound (const Key & key ) const |
| QMultiMap::size_type | remove (const Key & key ) |
| QMultiMap::size_type | remove (const Key & key , const T & value ) |
| QMultiMap::size_type | removeIf (Predicate pred ) |
| QMultiMap::iterator | replace (const Key & key , const T & value ) |
| QMultiMap::size_type | size () const |
| void | swap (QMultiMap<Key, T> & other ) |
| T | take (const Key & key ) |
| std::multimap<Key, T> | toStdMultiMap () const & |
| QList<Key> | uniqueKeys () const |
| QMultiMap<Key, T> & | unite (const QMultiMap<Key, T> & other ) |
| QMultiMap<Key, T> & | unite (QMultiMap<Key, T> && other ) |
| QMultiMap::iterator | upperBound (const Key & key ) |
| QMultiMap::const_iterator | upperBound (const Key & key ) const |
| T | value (const Key & key , const T & defaultValue = T()) const |
| QList<T> | values () const |
| QList<T> | values (const Key & key ) const |
| QMultiMap<Key, T> & | operator= (const QMultiMap<Key, T> & other ) |
| QMultiMap<Key, T> & | operator= (QMultiMap<Key, T> && other ) |
| qsizetype | erase_if (QMultiMap<Key, T> & map , Predicate pred ) |
| bool | operator!= (const QMultiMap<Key, T> & lhs , const QMultiMap<Key, T> & rhs ) |
| QMultiMap<Key, T> | operator+ (const QMultiMap<Key, T> & lhs , const QMultiMap<Key, T> & rhs ) |
| QMultiMap<Key, T> | operator+= (QMultiMap<Key, T> & lhs , const QMultiMap<Key, T> & rhs ) |
| QDataStream & | operator<< (QDataStream & out , const QMultiMap<Key, T> & map ) |
| bool | operator== (const QMultiMap<Key, T> & lhs , const QMultiMap<Key, T> & rhs ) |
| QDataStream & | operator>> (QDataStream & in , QMultiMap<Key, T> & map ) |
QMultiMap<Key, T> 是一種 Qt 一般 容器類 . It stores (key, value) pairs and provides fast lookup by key.
QMultiMap and QMultiHash 提供非常類似的功能。差異是：
Here's an example QMultiMap with
QString
鍵和
int
值：
QMultiMap<QString, int> multimap;
To insert a (key, value) pair into the multi map, you can use insert ():
multimap.insert("a", 1); multimap.insert("b", 3); multimap.insert("c", 7); multimap.insert("c", -5);
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 () 或 value ():
int num2 = multimap.value("a"); // 1 int num3 = multimap.value("thirteen"); // not found; 0 int num3 = 0; auto it = multimap.constFind("b"); if (it != multimap.cend()) { num3 = it.value(); }
If there is no item with the specified key in the map, these functions return a 默認構造值 .
If you want to check whether the map contains a certain key, use contains ():
int timeout = 30; if (multimap.contains("TIMEOUT")) timeout = multimap.value("TIMEOUT"); // better: auto it = multimap.find("TIMEOUT"); if (it != multimap.end()) timeout = it.value();
There is also a value () overload that uses its second argument as a default value if there is no item with the specified key:
int timeout = multimap.value("TIMEOUT", 30);
If you want to navigate through all the (key, value) pairs stored in a QMultiMap, you can use an iterator. QMultiMap provides both Java 風格迭代器 ( QMultiMapIterator and QMutableMultiMapIterator ) 和 STL 樣式迭代器 ( QMultiMap::const_iterator and QMultiMap::iterator ). Here's how to iterate over a QMultiMap< QString , int> using a Java-style iterator:
QMultiMapIterator<QString, int> i(multimap); while (i.hasNext()) { i.next(); cout << qPrintable(i.key()) << ": " << i.value() << endl; }
Here's the same code, but using an STL-style iterator this time:
for (auto i = multimap.cbegin(), end = multimap.cend(); i != end; ++i) cout << qPrintable(i.key()) << ": " << i.value() << endl;
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:
multimap.insert("plenty", 100); multimap.insert("plenty", 2000); // multimap.size() == 2
If you want to retrieve all the values for a single key, you can use values(const Key &key), which returns a QList <T>:
QList<int> values = multimap.values("plenty"); for (auto i : std::as_const(values)) cout << i << endl;
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:
auto i = multimap.find("plenty"); while (i != map.end() && i.key() == "plenty") { cout << i.value() << endl; ++i; } // better: auto [i, end] = multimap.equal_range("plenty"); while (i != end) { cout << i.value() << endl; ++i; }
If you only need to extract the values from a map (not the keys), you can also use range-based for:
QMap<QString, int> multimap; ... for (int value : std::as_const(multimap)) cout << value << endl;
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:
QMultiMap<QString, int> map1, map2, map3; map1.insert("plenty", 100); map1.insert("plenty", 2000); // map1.size() == 2 map2.insert("plenty", 5000); // map2.size() == 1 map3 = map1 + map2; // map3.size() == 3
QMultiMap's key and value data types must be
可賦值數據類型
. This covers most data types you are likely to encounter, but the compiler won't let you, for example, store a
QWidget
作為值；取而代之，存儲
QWidget
*. In addition, QMultiMap's key type must provide operator<().
QMap
uses it to keep its items sorted, and assumes that two keys
x
and
y
are equal if neither
x < y
nor
y < x
為 true。
範例：
#ifndef EMPLOYEE_H #define EMPLOYEE_H class Employee { public: Employee() {} Employee(const QString &name, QDate dateOfBirth); ... private: QString myName; QDate myDateOfBirth; }; inline bool operator<(const Employee &e1, const Employee &e2) { if (e1.name() != e2.name()) return e1.name() < e2.name(); return e1.dateOfBirth() < e2.dateOfBirth(); } #endif // EMPLOYEE_H
In the example, we start by comparing the employees' names. If they're equal, we compare their dates of birth to break the tie.
另請參閱 QMultiMapIterator , QMutableMultiMapIterator ，和 QMultiHash .
Qt 樣式同義詞 QMultiMap::const_iterator .
Qt 樣式同義詞 QMultiMap::iterator .
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.
另請參閱 QKeyValueIterator .
[alias]
QMultiMap::
difference_type
typedef 對於 ptrdiff_t。為兼容 STL 提供。
[alias]
QMultiMap::
key_type
typedef 對於 Key。為兼容 STL 提供。
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.
另請參閱 QKeyValueIterator .
[alias]
QMultiMap::
mapped_type
typedef 對於 T。為兼容 STL 提供。
[alias]
QMultiMap::
size_type
typedef 對於 int。為兼容 STL 提供。
[since 6.4]
auto
QMultiMap::
asKeyValueRange
() &
[since 6.4]
auto
QMultiMap::
asKeyValueRange
() &&
[since 6.4]
auto
QMultiMap::
asKeyValueRange
() const &
[since 6.4]
auto
QMultiMap::
asKeyValueRange
() const &&
Returns a range object that allows iteration over this multi map as key/value pairs. For instance, this range object can be used in a range-based for loop, in combination with a structured binding declaration:
QMultiMap<QString, int> map; map.insert("January", 1); map.insert("February", 2); // ... map.insert("December", 12); for (auto [key, value] : map.asKeyValueRange()) { cout << qPrintable(key) << ": " << value << endl; --value; // convert to JS month indexing }
Note that both the key and the value obtained this way are references to the ones in the multi map. Specifically, mutating the value will modify the map itself.
This function was introduced in Qt 6.4.
另請參閱 QKeyValueIterator .
Constructs an empty multi map.
另請參閱 clear ().
Constructs a multi map with a copy of each of the elements in the initializer list list .
[explicit, since 6.0]
QMultiMap::
QMultiMap
(const
QMap
<
Key
,
T
> &
other
)
Constructs a multi map as a copy of other .
該函數在 Qt 6.0 引入。
[explicit, since 6.0]
QMultiMap::
QMultiMap
(
QMap
<
Key
,
T
> &&
other
)
若 other is shared, constructs a multi map as a copy of other . Otherwise, constructs a multi map by moving the elements from other .
該函數在 Qt 6.0 引入。
[explicit]
QMultiMap::
QMultiMap
(const
std::multimap
<
Key
,
T
> &
other
)
構造副本為 other .
另請參閱 toStdMultiMap ().
[explicit]
QMultiMap::
QMultiMap
(
std::multimap
<
Key
,
T
> &&
other
)
Constructs a multi map by moving from other .
另請參閱 toStdMultiMap ().
[default]
QMultiMap::
QMultiMap
(
QMultiMap
<
Key
,
T
> &&
other
)
Move-constructs a QMultiMap instance, making it point at the same object that other 所指嚮的。
[default]
QMultiMap::
QMultiMap
(const
QMultiMap
<
Key
,
T
> &
other
)
構造副本為 other .
This operation occurs in 常量時間 , because QMultiMap is 隱式共享 . 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 綫性時間 .
另請參閱 operator= ().
[default]
QMultiMap::
~QMultiMap
()
Destroys the multi map. References to the values in the multi map, and all iterators over this multi map, become invalid.
返迴 STL 樣式迭代器 pointing to the first item in the multi map.
另請參閱 constBegin () 和 end ().
這是重載函數。
返迴常量 STL 樣式迭代器 pointing to the first item in the multi map.
返迴常量 STL 樣式迭代器 pointing to the imaginary item after the last item in the multi map.
Removes all items from the multi map.
另請參閱 remove ().
返迴常量 STL 樣式迭代器 pointing to the first item in the multi map.
返迴常量 STL 樣式迭代器 pointing to the imaginary item after the last item in the multi map.
另請參閱 constBegin () 和 end ().
Returns an const iterator pointing to the item with key key in the multi map.
If the multi map contains no item with key key ，函數返迴 constEnd ().
另請參閱 find () and QMultiMap::constFind().
Returns an iterator pointing to the item with key key and the value value in the map.
If the map contains no such item, the function returns constEnd ().
另請參閱 QMap::constFind ().
返迴常量 STL 樣式迭代器 pointing to the first entry in the multi map.
另請參閱 keyValueBegin ().
返迴常量 STL 樣式迭代器 pointing to the imaginary entry after the last entry in the multi map.
另請參閱 constKeyValueBegin ().
返迴
true
if the multi map contains an item with key
key
；否則返迴
false
.
另請參閱 count ().
返迴
true
if the multi map contains an item with key
key
and value
value
；否則返迴
false
.
另請參閱 count ().
Returns the number of items associated with key key .
另請參閱 contains () 和 QMultiMap::count ().
Returns the number of items with key key and value value .
另請參閱 contains () 和 QMultiMap::count ().
這是重載函數。
如同 size ().
此函數為兼容 STL (標準模闆庫) 提供。它相當於 isEmpty (), returning true if the map is empty; otherwise returning false.
返迴 STL 樣式迭代器 pointing to the imaginary item after the last item in the multi map.
這是重載函數。
Returns a pair of iterators delimiting the range of values
[first, second)
, that are stored under
key
.
這是重載函數。
Removes the (key, value) pair pointed to by the iterator pos from the multi map, and returns an iterator to the next item in the map.
注意： The iterator pos must be valid and dereferenceable.
另請參閱 remove ().
[since 6.0]
QMultiMap::iterator
QMultiMap::
erase
(
QMultiMap::const_iterator
first
,
QMultiMap::const_iterator
last
)
Removes the (key, value) pairs pointed to by the iterator range [ first , last ) from the multi map. Returns an iterator to the item in the multi map following the last removed element.
注意：
範圍
[first, last)
must
be a valid range in
*this
.
該函數在 Qt 6.0 引入。
另請參閱 remove ().
Returns an iterator pointing to the item with key key in the multi map.
If the multi map contains no item with key key ，函數返迴 end ().
If the map contains multiple items with key 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:
auto i = multimap.find("plenty"); while (i != map.end() && i.key() == "plenty") { cout << i.value() << endl; ++i; } // better: auto [i, end] = multimap.equal_range("plenty"); while (i != end) { cout << i.value() << endl; ++i; }
另請參閱 constFind (), value (), values (), lowerBound ()，和 upperBound ().
這是重載函數。
這是重載函數。
Returns a const iterator pointing to the item with the given key and value in the map.
If the map contains no such item, the function returns end ().
If the map contains multiple items with the specified key , this function returns a const iterator that points to the most recently inserted value.
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 常量時間 .
另請參閱 last (), firstKey ()，和 isEmpty ().
這是重載函數。
Returns a reference to the smallest key in the multi map. This function assumes that the multi map is not empty.
This executes in 常量時間 .
另請參閱 lastKey (), first (), keyBegin ()，和 isEmpty ().
Inserts a new item with the key key 和值 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.)
另請參閱 replace ().
這是重載函數。
Inserts a new item with the key key and value value and with hint pos suggesting where to do the insert.
若 constBegin () is used as hint it indicates that the key is less than any key in the multi map while constEnd () suggests that the key is (strictly) larger than any key in the multi map. Otherwise the hint should meet the condition ( pos - 1). key () < key <= pos. key (). If the hint 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 常量時間 .
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 logarithmic time .
注意： 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 pos multi map.
返迴
true
if the multi map contains no items; otherwise returns false.
另請參閱 size ().
這是重載函數。
返迴第 1 個鍵具有值 value ，或 defaultKey if the multi map contains no item with value value . If no defaultKey is provided the function returns a default-constructed key .
此函數可能很慢 ( 綫性時間 )，因為 QMultiMap 's internal data structure is optimized for fast lookup by key, not by value.
返迴常量 STL 樣式迭代器 pointing to the first key in the multi map.
返迴常量 STL 樣式迭代器 pointing to the imaginary item after the last key in the multi map.
另請參閱 keyBegin () 和 lastKey ().
返迴 STL 樣式迭代器 pointing to the first entry in the multi map.
另請參閱 keyValueEnd ().
返迴常量 STL 樣式迭代器 pointing to the first entry in the multi map.
另請參閱 keyValueEnd ().
返迴 STL 樣式迭代器 pointing to the imaginary entry after the last entry in the multi map.
另請參閱 keyValueBegin ().
返迴常量 STL 樣式迭代器 pointing to the imaginary entry after the last entry in the multi map.
另請參閱 keyValueBegin ().
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 綫性時間 . The time and memory use that entails can be avoided by iterating from keyBegin () 到 keyEnd ().
這是重載函數。
Returns a list containing all the keys associated with value value in ascending order.
此函數可能很慢 ( 綫性時間 )，因為 QMultiMap 's internal data structure is optimized for fast lookup by key, not by value.
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 logarithmic time .
另請參閱 first (), lastKey ()，和 isEmpty ().
這是重載函數。
Returns a reference to the largest key in the multi map. This function assumes that the multi map is not empty.
This executes in logarithmic time .
另請參閱 firstKey (), last (), keyEnd ()，和 isEmpty ().
Returns an iterator pointing to the first item with key key in the map. If the map contains no item with key key , the function returns an iterator to the nearest item with a greater key.
範例：
QMultiMap<int, QString> multimap; multimap.insert(1, "one"); multimap.insert(5, "five"); multimap.insert(5, "five (2)"); multimap.insert(10, "ten"); multimap.lowerBound(0); // returns iterator to (1, "one") multimap.lowerBound(1); // returns iterator to (1, "one") multimap.lowerBound(2); // returns iterator to (5, "five") multimap.lowerBound(5); // returns iterator to (5, "five") multimap.lowerBound(6); // returns iterator to (10, "ten") multimap.lowerBound(10); // returns iterator to (10, "ten") multimap.lowerBound(999); // returns end()
If the map contains multiple items with key 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:
QMap<QString, int> multimap; ... QMap<QString, int>::const_iterator i = multimap.lowerBound("HDR"); QMap<QString, int>::const_iterator upperBound = multimap.upperBound("HDR"); while (i != upperBound) { cout << i.value() << endl; ++i; }
另請參閱 upperBound () 和 find ().
這是重載函數。
Removes all the items that have the key key from the multi map. Returns the number of items removed.
Removes all the items that have the key key and value value from the multi map. Returns the number of items removed.
[since 6.1]
template <typename Predicate>
QMultiMap::size_type
QMultiMap::
removeIf
(
Predicate
pred
)
Removes all elements for which the predicate pred returns true from the multi map.
The function supports predicates which take either an argument of type
QMultiMap<Key, T>::iterator
, or an argument of type
std::pair<const Key &, T &>
.
Returns the number of elements removed, if any.
This function was introduced in Qt 6.1.
Inserts a new item with the key key 和值 value .
If there is already an item with the key key , that item's value is replaced with value .
If there are multiple items with the key key , the most recently inserted item's value is replaced with value .
另請參閱 insert ().
Returns the number of (key, value) pairs in the multi map.
Swaps multi map other with this multi map. This operation is very fast and never fails.
Removes the item with the key 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 默認構造值 . If there are multiple items for key in the map, only the most recently inserted one is removed and returned.
若不使用返迴值， remove () 效率更高。
另請參閱 remove ().
Returns an STL multi map equivalent to this QMultiMap .
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.
Inserts all the items in the other map into this map. If a key is common to both maps, the resulting map will contain the key multiple times.
Moves all the items from the other map into this map. If a key is common to both maps, the resulting map will contain the key multiple times.
若 other is shared, then the items will be copied instead.
Returns an iterator pointing to the item that immediately follows the last item with key key in the map. If the map contains no item with key key , the function returns an iterator to the nearest item with a greater key.
範例：
QMultiMap<int, QString> multimap; multimap.insert(1, "one"); multimap.insert(5, "five"); multimap.insert(5, "five (2)"); multimap.insert(10, "ten"); multimap.upperBound(0); // returns iterator to (1, "one") multimap.upperBound(1); // returns iterator to (5, "five") multimap.upperBound(2); // returns iterator to (5, "five") multimap.lowerBound(5); // returns iterator to (5, "five (2)") multimap.lowerBound(6); // returns iterator to (10, "ten") multimap.upperBound(10); // returns end() multimap.upperBound(999); // returns end()
另請參閱 lowerBound () 和 find ().
這是重載函數。
Returns the value associated with the key key .
If the multi map contains no item with key key ，函數返迴 defaultValue . If no defaultValue is specified, the function returns a 默認構造值 . If there are multiple items for key in the multi map, the value of the most recently inserted one is returned.
另請參閱 key (), values ()，和 contains ().
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.
Returns a list containing all the values associated with key key , from the most recently inserted to the least recently inserted one.
[default]
QMultiMap
<
Key
,
T
> &QMultiMap::
operator=
(const
QMultiMap
<
Key
,
T
> &
other
)
賦值 other to this multi map and returns a reference to this multi map.
[default]
QMultiMap
<
Key
,
T
> &QMultiMap::
operator=
(
QMultiMap
<
Key
,
T
> &&
other
)
移動賦值 other 到此 QMultiMap 實例。
[since 6.1]
template <typename Key, typename T, typename Predicate>
qsizetype
erase_if
(
QMultiMap
<
Key
,
T
> &
map
,
Predicate
pred
)
Removes all elements for which the predicate pred returns true from the multi map map .
The function supports predicates which take either an argument of type
QMultiMap<Key, T>::iterator
, or an argument of type
std::pair<const Key &, T &>
.
Returns the number of elements removed, if any.
This function was introduced in Qt 6.1.
返迴
true
if
lhs
不等於
rhs
；否則返迴
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
operator==()
.
另請參閱 operator== ().
Returns a map that contains all the items in the lhs map in addition to all the items in rhs . If a key is common to both maps, the resulting map will contain the key multiple times.
另請參閱 operator+= ().
Inserts all the items in the rhs map into the lhs map and returns the resulting map.
另請參閱 insert () 和 operator+ ().
Writes the multi map map 到流 out .
This function requires the key and value types to implement
operator<<()
.
另請參閱 QDataStream 運算符格式 .
返迴
true
if
lhs
等於
rhs
；否則返迴 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
operator==()
.
另請參閱 operator!= ().
讀取映射從流 in into map .
This function requires the key and value types to implement
operator>>()
.
另請參閱 QDataStream 運算符格式 .