QMultiHash 類是方便 QHash 子類，提供多值哈希。 更多...
| 頭： | #include <QMultiHash> |
| 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 |
| const_key_value_iterator | |
| key_value_iterator |
| QMultiHash () | |
| QMultiHash (std::initializer_list<std::pair<Key, T>> list ) | |
| QMultiHash (InputIterator begin , InputIterator end ) | |
| QMultiHash (const QHash<Key, T> & other ) | |
| auto | asKeyValueRange () & |
| auto | asKeyValueRange () const & |
| auto | asKeyValueRange () && |
| auto | asKeyValueRange () const && |
| QMultiHash::iterator | begin () |
| QMultiHash::const_iterator | begin () const |
| QMultiHash::const_iterator | cbegin () const |
| QMultiHash::const_iterator | cend () const |
| void | clear () |
| QMultiHash::const_iterator | constBegin () const |
| QMultiHash::const_iterator | constEnd () const |
| QMultiHash::const_iterator | constFind (const Key & key , const T & value ) const |
| QMultiHash::const_key_value_iterator | constKeyValueBegin () const |
| QMultiHash::const_key_value_iterator | constKeyValueEnd () const |
| bool | contains (const Key & key , const T & value ) const |
| qsizetype | count (const Key & key , const T & value ) const |
| QMultiHash::iterator | emplace (const Key & key , Args &&... args ) |
| QMultiHash::iterator | emplace (Key && key , Args &&... args ) |
| QMultiHash::iterator | emplaceReplace (const Key & key , Args &&... args ) |
| QMultiHash::iterator | emplaceReplace (Key && key , Args &&... args ) |
| QMultiHash::iterator | end () |
| QMultiHash::const_iterator | end () const |
| QPair<QMultiHash::iterator, QMultiHash::iterator> | equal_range (const Key & key ) |
| QPair<QMultiHash::const_iterator, QMultiHash::const_iterator> | equal_range (const Key & key ) const |
| QMultiHash::iterator | find (const Key & key , const T & value ) |
| QMultiHash::const_iterator | find (const Key & key , const T & value ) const |
| QMultiHash::iterator | insert (const Key & key , const T & value ) |
| Key | key (const T & value ) const |
| Key | key (const T & value , const Key & defaultKey ) const |
| QMultiHash::key_iterator | keyBegin () const |
| QMultiHash::key_iterator | keyEnd () const |
| QMultiHash::key_value_iterator | keyValueBegin () |
| QMultiHash::const_key_value_iterator | keyValueBegin () const |
| QMultiHash::key_value_iterator | keyValueEnd () |
| QMultiHash::const_key_value_iterator | keyValueEnd () const |
| QList<Key> | keys () const |
| qsizetype | remove (const Key & key ) |
| qsizetype | remove (const Key & key , const T & value ) |
| qsizetype | removeIf (Predicate pred ) |
| QMultiHash::iterator | replace (const Key & key , const T & value ) |
| void | swap (QMultiHash<Key, T> & other ) |
| T | take (const Key & key ) |
| QList<Key> | uniqueKeys () const |
| QMultiHash<Key, T> & | unite (const QMultiHash<Key, T> & other ) |
| QMultiHash<Key, T> & | unite (const QHash<Key, T> & other ) |
| T | value (const Key & key ) const |
| T | value (const Key & key , const T & defaultValue ) const |
| QList<T> | values () const |
| QList<T> | values (const Key & key ) const |
| QMultiHash<Key, T> | operator+ (const QMultiHash<Key, T> & other ) const |
| QMultiHash<Key, T> & | operator+= (const QMultiHash<Key, T> & other ) |
| T & | operator[] (const Key & key ) |
| qsizetype | erase_if (QMultiHash<Key, T> & hash , Predicate pred ) |
| size_t | qHash (const QMultiHash<Key, T> & key , size_t seed = 0) |
| QDataStream & | operator<< (QDataStream & out , const QMultiHash<Key, T> & hash ) |
| QDataStream & | operator>> (QDataStream & in , QMultiHash<Key, T> & hash ) |
QMultiHash<Key, T> 是一種 Qt 一般 容器類 . It inherits QHash and extends it with a few convenience functions that make it more suitable than QHash for storing multi-valued hashes. A multi-valued hash is a hash that allows multiple values with the same key.
QMultiHash mostly mirrors QHash 's API. For example, you can use isEmpty() to test whether the hash is empty, and you can traverse a QMultiHash using QHash 的迭代器類 (例如： QHashIterator ). But opposed to QHash , it provides an insert () function that allows the insertion of multiple items with the same key. The replace () function corresponds to QHash::insert (). It also provides convenient operator+() and operator+=().
不像 QMultiMap , QMultiHash does not provide and ordering of the inserted items. The only guarantee is that items that share the same key will appear consecutively, from the most recently to the least recently inserted value.
範例：
QMultiHash<QString, int> hash1, hash2, hash3; hash1.insert("plenty", 100); hash1.insert("plenty", 2000); // hash1.size() == 2 hash2.insert("plenty", 5000); // hash2.size() == 1 hash3 = hash1 + hash2; // hash3.size() == 3
不像 QHash , QMultiHash provides no operator[]. Use value () 或 replace () if you want to access the most recently inserted item with a certain key.
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 = hash.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.
A more efficient approach is to call find () to get the STL-style iterator for the first item with a key and iterate from there:
auto i = hash.constFind("plenty"); while (i != hash.cend() && i.key() == "plenty") { cout << i.value() << endl; ++i; }
QMultiHash's key and value data types must be 可賦值數據類型 。例如，無法存儲 QWidget 作為值；取而代之，存儲 QWidget *. In addition, QMultiHash's key type must provide operator==(), and there must also be a qHash () function in the type's namespace that returns a hash value for an argument of the key's type. See the QHash 文檔編製瞭解細節。
另請參閱 QHash , QHashIterator , QMutableHashIterator ，和 QMultiMap .
The QMap::const_key_value_iterator typedef provides an STL-style const iterator for QMultiHash and QMultiHash .
QMultiHash::const_key_value_iterator is essentially the same as QMultiHash::const_iterator with the difference that operator*() returns a key/value pair instead of a value.
另請參閱 QKeyValueIterator .
The QMap::key_value_iterator typedef provides an STL-style iterator for QMultiHash and QMultiHash .
QMultiHash::key_value_iterator is essentially the same as QMultiHash::iterator with the difference that operator*() returns a key/value pair instead of a value.
另請參閱 QKeyValueIterator .
Inserts a new element into the container. This new element is constructed in-place using args as the arguments for its construction.
If there is already an item with the same key in the hash, this function will simply create a new one. (This behavior is different from replace (), which overwrites the value of an existing item.)
Returns an iterator pointing to the new element.
另請參閱 insert .
Inserts a new element into the container. This new element is constructed in-place using args as the arguments for its construction.
If there is already an item with the same key in the hash, that item's value is replaced with a value constructed from args .
Returns an iterator pointing to the new element.
返迴值關聯 key .
若哈希包含的項不具有 key ，函數返迴 defaultValue ，或 默認構造值 if this parameter has not been supplied.
If there are multiple items for the key in the hash, the value of the most recently inserted one is returned.
Returns the first key mapped to value . If the hash contains no item mapped to value ，返迴 defaultKey ，或 default-constructed key if this parameter has not been supplied.
此函數可能很慢 ( 綫性時間 )，因為 QMultiHash 's internal data structure is optimized for fast lookup by key, not by value.
[since 6.4]
auto
QMultiHash::
asKeyValueRange
() &
[since 6.4]
auto
QMultiHash::
asKeyValueRange
() &&
[since 6.4]
auto
QMultiHash::
asKeyValueRange
() const &
[since 6.4]
auto
QMultiHash::
asKeyValueRange
() const &&
Returns a range object that allows iteration over this hash 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:
QMultiHash<QString, int> hash; hash.insert("January", 1); hash.insert("February", 2); // ... hash.insert("December", 12); for (auto [key, value] : hash.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 hash. Specifically, mutating the value will modify the hash itself.
This function was introduced in Qt 6.4.
另請參閱 QKeyValueIterator .
構造空哈希。
Constructs a multi-hash with a copy of each of the elements in the initializer list list .
This function is only available if the program is being compiled in C++11 mode.
Constructs a multi-hash with a copy of each of the elements in the iterator range [
begin
,
end
). Either the elements iterated by the range must be objects with
第一
and
second
data members (like
QPair
,
std::pair
, etc.) convertible to
Key
and to
T
respectively; or the iterators must have
key()
and
value()
member functions, returning a key convertible to
Key
and a value convertible to
T
分彆。
[explicit]
QMultiHash::
QMultiHash
(const
QHash
<
Key
,
T
> &
other
)
構造副本為 other (which can be a QHash or a QMultiHash).
返迴 STL 樣式迭代器 指嚮哈希中的首項。
另請參閱 constBegin () 和 end ().
這是重載函數。
返迴常量 STL 樣式迭代器 指嚮哈希中的首項。
返迴常量 STL 樣式迭代器 pointing to the imaginary item after the last item in the hash.
Removes all items from the hash and frees up all memory used by it.
另請參閱 remove ().
返迴常量 STL 樣式迭代器 指嚮哈希中的首項。
返迴常量 STL 樣式迭代器 pointing to the imaginary item after the last item in the hash.
另請參閱 constBegin () 和 end ().
返迴迭代器指嚮的項具有 key 和 value 在哈希中。
If the hash contains no such item, the function returns constEnd ().
返迴常量 STL 樣式迭代器 指嚮第一哈希條目。
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 hash.
另請參閱 constKeyValueBegin ().
返迴
true
若哈希包含的項具有
key
and
value
；否則返迴
false
.
另請參閱 contains().
Returns the number of items with the key and value .
另請參閱 count().
返迴 STL 樣式迭代器 pointing to the imaginary item after the last item in the hash.
這是重載函數。
Returns a pair of iterators delimiting the range of values
[first, second)
, that are stored under
key
. If the range is empty then both iterators will be equal to
end
().
這是重載函數。
返迴迭代器指嚮的項具有 key and value . If the hash contains no such item, the function returns end ().
If the hash contains multiple items with the key and value , the iterator returned points to the most recently inserted item.
這是重載函數。
插入新項具有 key 和值 value .
If there is already an item with the same key in the hash, 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 ().
返迴常量 STL 樣式迭代器 指嚮哈希中的第 1 個 Key。
另請參閱 keyEnd ().
返迴常量 STL 樣式迭代器 pointing to the imaginary item after the last key in the hash.
另請參閱 keyBegin ().
返迴 STL 樣式迭代器 指嚮第一哈希條目。
另請參閱 keyValueEnd ().
返迴常量 STL 樣式迭代器 指嚮第一哈希條目。
另請參閱 keyValueEnd ().
返迴 STL 樣式迭代器 pointing to the imaginary entry after the last entry in the hash.
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 hash.
另請參閱 keyValueBegin ().
Returns a list containing all the keys in the hash, in an arbitrary order. Keys that occur multiple times in the hash 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 ().
Removes all the items that have the key from the hash. Returns the number of items removed.
另請參閱 remove().
Removes all the items that have the key and the value value from the hash. Returns the number of items removed.
另請參閱 remove ().
[since 6.1]
template <typename Predicate>
qsizetype
QMultiHash::
removeIf
(
Predicate
pred
)
Removes all elements for which the predicate pred returns true from the multi hash.
The function supports predicates which take either an argument of type
QMultiHash<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.
插入新項具有 key 和值 value .
If there is already an item with the key , that item's value is replaced with value .
If there are multiple items with the key , the most recently inserted item's value is replaced with value .
另請參閱 insert ().
交換哈希 other with this hash. This operation is very fast and never fails.
Removes the item with the key from the hash and returns the value associated with it.
If the item does not exist in the hash, the function simply returns a 默認構造值 . If there are multiple items for key in the hash, only the most recently inserted one is removed.
若不使用返迴值， remove () 效率更高。
另請參閱 remove ().
Returns a list containing all the keys in the map. Keys that occur multiple times in the map occur only once in the returned list.
Inserts all the items in the other hash into this hash and returns a reference to this hash.
另請參閱 insert ().
[since 6.0]
QMultiHash
<
Key
,
T
> &QMultiHash::
unite
(const
QHash
<
Key
,
T
> &
other
)
Inserts all the items in the other hash into this hash and returns a reference to this hash.
該函數在 Qt 6.0 引入。
另請參閱 insert ().
Returns a list containing all the values in the hash, in an arbitrary order. 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.
The order is guaranteed to be the same as that used by keys ().
This function creates a new list, in 綫性時間 . The time and memory use that entails can be avoided by iterating from keyValueBegin () 到 keyValueEnd ().
這是重載函數。
Returns a list of all the values associated with the key , from the most recently inserted to the least recently inserted.
Returns a hash that contains all the items in this hash in addition to all the items in other . If a key is common to both hashes, the resulting hash will contain the key multiple times.
另請參閱 operator+= ().
Inserts all the items in the other hash into this hash and returns a reference to this hash.
返迴值關聯 key 作為可修改引用。
若哈希包含的項不具有 key , the function inserts a 默認構造值 into the hash with the key , and returns a reference to it.
If the hash contains multiple items with the key , this function returns a reference to the most recently inserted value.
[since 6.1]
template <typename Key, typename T, typename Predicate>
qsizetype
erase_if
(
QMultiHash
<
Key
,
T
> &
hash
,
Predicate
pred
)
Removes all elements for which the predicate pred returns true from the multi hash hash .
The function supports predicates which take either an argument of type
QMultiHash<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.
返迴哈希值為 key ，使用 seed 做計算種子。
類型
T
must be supported by qHash().
寫入哈希 hash 到流 out .
This function requires the key and value types to implement
operator<<()
.
另請參閱 序列化 Qt 數據類型 .
讀取哈希從流 in into hash .
This function requires the key and value types to implement
operator>>()
.
另請參閱 序列化 Qt 數據類型 .