QMultiHash Class

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

QList<int> values = hash.values("plenty");
for (int i = 0; i < values.size(); ++i)
    cout << values.at(i) << Qt::endl;

QMultiHash<QString, int>::iterator i = hash.find("plenty");
while (i != hash.end() && i.key() == "plenty") {
    cout << i.value() << Qt::endl;
    ++i;
}

Member Function Documentation

QMultiHash::QMultiHash(const QHash<Key, T> &other)

Constructs a copy of other (which can be a QHash or a QMultiHash).

See also operator=().

template <typename InputIterator> QMultiHash::QMultiHash(InputIterator begin, InputIterator end)

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 first 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 respectively.

This function was introduced in Qt 5.14.

QMultiHash::QMultiHash(std::initializer_list<std::pair<Key, T>> list)

Constructs a multi-hash with a copy of each of the elements in the initializer list list.

This function was introduced in Qt 5.1.

QMultiHash::QMultiHash()

Constructs an empty hash.

typename QHash<Key, T>::const_iterator QMultiHash::constFind(const Key &key, const T &value) const

Returns an iterator pointing to the item with the key and the value in the hash.

If the hash contains no such item, the function returns constEnd().

This function was introduced in Qt 4.3.

See also QHash::constFind().

bool QMultiHash::contains(const Key &key, const T &value) const

Returns true if the hash contains an item with the key and value; otherwise returns false.

This function was introduced in Qt 4.3.

See also QHash::contains().

int QMultiHash::count(const Key &key, const T &value) const

Returns the number of items with the key and value.

This function was introduced in Qt 4.3.

See also QHash::count().

typename QHash<Key, T>::iterator QMultiHash::find(const Key &key, const T &value)

Returns an iterator pointing to the item with the 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.

This function was introduced in Qt 4.3.

See also QHash::find().

typename QHash<Key, T>::const_iterator QMultiHash::find(const Key &key, const T &value) const

This is an overloaded function.

This function was introduced in Qt 4.3.

typename QHash<Key, T>::iterator QMultiHash::insert(const Key &key, const T &value)

Inserts a new item with the key and a value of 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.)

See also replace().

int QMultiHash::remove(const Key &key, const T &value)

Removes all the items that have the key and the value value from the hash. Returns the number of items removed.

This function was introduced in Qt 4.3.

See also QHash::remove().

typename QHash<Key, T>::iterator QMultiHash::replace(const Key &key, const T &value)

Inserts a new item with the key and a value of 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.

See also insert().

void QMultiHash::swap(QMultiHash<K, V> &other)

Swaps hash other with this hash. This operation is very fast and never fails.

This function was introduced in Qt 4.8.

QList<Key> QMultiHash::uniqueKeys() const

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.

This function was introduced in Qt 5.13.

See also keys() and values().

QMultiHash<K, V> &QMultiHash::unite(const QMultiHash<K, V> &other)

Inserts all the items in the other hash into this hash and returns a reference to this hash.

This function was introduced in Qt 5.13.

See also insert().

QList<T> QMultiHash::values(const Key &key) const

This is an overloaded function.

Returns a list of all the values associated with the key, from the most recently inserted to the least recently inserted.

See also count() and insert().

QMultiHash<K, V> QMultiHash::operator+(const QMultiHash<K, V> &other) const

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.

See also operator+=().

QMultiHash<K, V> &QMultiHash::operator+=(const QMultiHash<K, V> &other)

Inserts all the items in the other hash into this hash and returns a reference to this hash.

See also unite() and insert().