STL style non-const iterator for QMultiHash. More...

Public Typedefs
using	iterator_category = std::forward_iterator_tag

using	pointer = Val *

using	reference = Val &

using	size_type = typename std::unordered_multimap< Key, Val, Hash, KeyEqual >::difference_type

Public Methods
	iterator () = default

const Key &	key () const

bool	operator!= (iterator other) const

Val &	operator* () const

iterator	operator+ (size_type n) const

iterator &	operator++ ()

iterator	operator++ (int)

iterator &	operator+= (size_type n)

iterator	operator- (size_type n) const

iterator &	operator-= (size_type n)

Val *	operator-> () const

bool	operator== (iterator other) const

std::pair< const Key, Val > &	pair () const

Val &	value () const

Friends
class	QMultiHash< Key, Val, Hash, KeyEqual >

Detailed Description

template<typename Key, typename Val, typename Hash, typename KeyEqual>
class QMultiHash< Key, Val, Hash, KeyEqual >::iterator

The QMultiHash::iterator class provides an STL style non-const iterator for QMultiHash. QMultiHash features both STL style iterators and Java style iterators.

After construction you must initialize the iterator using a method like QMultiHash::constBegin(), QMultiHash::constEnd(), or QMultiHash::find() before you can start iterating. The following is an example which prints all of the (key, value) pairs in the container.

QMultiHash<QString, int> hash;
 
hash.insert("January",  1);
hash.insert("February", 2);
...
hash.insert("December", 12);
 
for (auto iter = hash.constBegin(); iter != hash.constEnd(); ++iter) {
  cout << iter.key() << ": " << iter.value() << endl;
}

Unlike QMap which orders its items by key, QHash stores its items in an arbitrary order. The only guarantee is items which share the same key will appear consecutively.

The following is an example which increments every value stored in the QHash by 2:

QMultiHash<QString, int>::iterator iter;
 
for (iter = hash.begin(); iter != hash.end(); ++iter) {
   iter.value() += 2;
}

Here is an example which removes all of the items whose key is a string starting with an underscore character.

QMultiHash<QString, int>::iterator iter = hash.begin();
 
while (iter != hash.end()) {
   if (iter.key().startsWith("_")) {
      iter = hash.erase(iter);
   } else {
      ++iter;
   }
}

The call to QMultiHash::erase() removes the item pointed to by the iterator from the hash and returns an iterator to the next item. Here is another way of removing an item while iterating:

QMultiHash<QString, int>::iterator iter = hash.begin();
 
while (iter != hash.end()) {
    QMultiHash<QString, int>::iterator prev = iter;
    ++iter;
 
    if (prev.key().startsWith("_")) {
        hash.erase(prev);
    }
}

It might be tempting to write code like the following. This code will potentially crash in ++iter, because iter is invalid after the call to erase().

// INCORRECT
while (i != hash.end()) {
    if (i.key().startsWith("_")) {
        hash.erase(i);
    }
 
    ++i;
}

See also: QMultiHash::const_iterator

Member Typedef Documentation

template<typename Key , typename Val , typename Hash , typename KeyEqual >

QMultiHash< Key, Val, Hash, KeyEqual >::iterator::iterator_category

A synonym for std::bidirectional_iterator_tag indicating this iterator is a bidirectional iterator.

template<typename Key , typename Val , typename Hash , typename KeyEqual >

QMultiHash< Key, Val, Hash, KeyEqual >::iterator::pointer

A synonym for value_type *.

template<typename Key , typename Val , typename Hash , typename KeyEqual >

QMultiHash< Key, Val, Hash, KeyEqual >::iterator::reference

A synonym for value_type &.

template<typename Key , typename Val , typename Hash , typename KeyEqual >

QMultiHash< Key, Val, Hash, KeyEqual >::iterator::size_type

A synonym for the native size type of this container.

Constructor & Destructor Documentation

template<typename Key , typename Val , typename Hash , typename KeyEqual >

QMultiHash< Key, Val, Hash, KeyEqual >::iterator::iterator ( )

default

Constructs an uninitialized iterator.

Methods like key(), value(), and operator++() must not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it.

See also: QMultiHash::begin(), QMultiHash::end()

Method Documentation

template<typename Key , typename Val , typename Hash , typename KeyEqual >

const Key & QMultiHash< Key, Val, Hash, KeyEqual >::iterator::key ( ) const

inline

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 QMultiHash::erase() followed by QMultiHash::insert() or QMultiHash::insertMulti().

See also: value()

template<typename Key , typename Val , typename Hash , typename KeyEqual >

bool QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator!= ( iterator other ) const

inline

Returns true if other points to a different item than this iterator, otherwise it returns false.

See also: operator==()

template<typename Key , typename Val , typename Hash , typename KeyEqual >

Val & QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator* ( ) const

inline

Equivalent to calling value().

See also: key()

template<typename Key , typename Val , typename Hash , typename KeyEqual >

iterator QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator+ ( size_type n ) const

inline

Returns an iterator to the item at n positions forward from this iterator. If n is negative the iterator goes backward.

This operation can be slow for large values of n.

See also: operator-()

template<typename Key , typename Val , typename Hash , typename KeyEqual >

iterator & QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator++ ( )

inline

The prefix ++ operator (++i) advances the iterator to the next item in the hash and returns an iterator to the new current item.

Calling this method on QMultiHash::end() leads to undefined behavior.

template<typename Key , typename Val , typename Hash , typename KeyEqual >

iterator QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator++ ( int )

inline

The postfix ++ operator (i++) advances the iterator to the next item in the hash and returns an iterator to the previously current item.

template<typename Key , typename Val , typename Hash , typename KeyEqual >

iterator & QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator+= ( size_type n )

inline

Advances the iterator by n items. If n is negative the iterator goes backward.

See also: operator-=(), operator+()

template<typename Key , typename Val , typename Hash , typename KeyEqual >

iterator QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator- ( size_type n ) const

inline

Returns an iterator to the item at n positions backward from this iterator. If n is negative the iterator goes forward.

This operation can be slow or large values of n.

See also: operator+()

template<typename Key , typename Val , typename Hash , typename KeyEqual >

iterator & QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator-= ( size_type n )

inline

Makes the iterator go back by n items. If n is negative the iterator goes forward.

See also: operator+=(), operator-()

template<typename Key , typename Val , typename Hash , typename KeyEqual >

Val * QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator-> ( ) const

inline

Returns a pointer to the current item's value.

See also: value()

template<typename Key , typename Val , typename Hash , typename KeyEqual >

bool QMultiHash< Key, Val, Hash, KeyEqual >::iterator::operator== ( iterator other ) const

inline

Returns true if other points to the same item as this iterator, otherwise it returns false.

See also: operator!=()

template<typename Key , typename Val , typename Hash , typename KeyEqual >

std::pair< const Key, Val > & QMultiHash< Key, Val, Hash, KeyEqual >::iterator::pair ( ) const

inline

Returns the current item's key and value as a pair.

template<typename Key , typename Val , typename Hash , typename KeyEqual >

Val & QMultiHash< Key, Val, Hash, KeyEqual >::iterator::value ( ) const

inline

Returns a reference to the value for the current item. You can change the value of an item by using value() on the left side of an assignment.

if (i.key() == "Hello") {
   i.value() = "Bonjour";
}

See also: key(), operator*()

Public Typedefs

Public Methods

Friends

Detailed Description

template<typename Key, typename Val, typename Hash, typename KeyEqual> class QMultiHash< Key, Val, Hash, KeyEqual >::iterator

Member Typedef Documentation

Constructor & Destructor Documentation

Method Documentation

template<typename Key, typename Val, typename Hash, typename KeyEqual>
class QMultiHash< Key, Val, Hash, KeyEqual >::iterator