const_iterator 類

class QMultiMap ::const_iterator

The QMultiMap::const_iterator 類提供 STL 樣式 const 迭代器為 QMultiMap . 更多...

• 所有成員列錶，包括繼承成員
• Deprecated members

公共類型

iterator_category

公共函數

	const_iterator ()
	const_iterator (const iterator & other )
const Key &	key () const
const T &	value () const
const T &	operator* () const
const_iterator &	operator++ ()
const_iterator	operator++ (int)
const_iterator &	operator-- ()
const_iterator	operator-- (int)
const T *	operator-> () const

相關非成員

bool	operator!= (const const_iterator & lhs , const const_iterator & rhs )
bool	operator== (const const_iterator & lhs , const const_iterator & rhs )

詳細描述

QMultiMap <Key, T>::const_iterator allows you to iterate over a QMultiMap . If you want to modify the QMultiMap as you iterate over it, you must use QMultiMap::iterator instead. It is generally good practice to use QMultiMap::const_iterator on a non-const QMultiMap as well, unless you need to change the QMultiMap through the iterator. Const iterators are slightly faster, and can improve code readability.

默認 QMultiMap::const_iterator constructor creates an uninitialized iterator. You must initialize it using a QMultiMap function like QMultiMap::cbegin (), QMultiMap::cend ()，或 QMultiMap::constFind () before you can start iterating. Here's a typical loop that prints all the (key, value) pairs stored in a map:

QMultiMap<QString, int> multi;
multimap.insert("January", 1);
multimap.insert("February", 2);
...
multimap.insert("December", 12);
for (auto i = multimap.cbegin(), end = multimap.cend(); i != end; ++i)
    cout << qPrintable(i.key()) << ": " << i.value() << endl;
					

Here's an example that removes all the items whose value is greater than 10:

QMultiMap<QString, int>::const_iterator i = multimap.cbegin();
while (i != multimap.cend()) {
    if (i.value() > 10)
        i = multimap.erase(i);
    else
        ++i;
}
					

不像 QMultiHash , which stores its items in an arbitrary order, QMultiMap stores its items ordered by key. Items that share the same key will appear consecutively, from the most recently to the least recently inserted value.

Multiple iterators can be used on the same multi 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 will become dangling iterators.

警告： Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read 隱式共享迭代器問題 .

另請參閱 QMultiMap::iterator , QMultiMap::key_iterator ，和 QMultiMap::const_key_value_iterator .

成員類型文檔編製

[alias] const_iterator:: iterator_category

同義詞 std::bidirectional_iterator_tag indicating this iterator is a bidirectional iterator.

成員函數文檔編製

const_iterator:: const_iterator ()

Constructs an uninitialized iterator.

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

另請參閱 QMultiMap::constBegin () 和 QMultiMap::constEnd ().

const_iterator:: const_iterator (const iterator & other )

構造副本為 other .

const Key &const_iterator:: key () const

Returns the current item's key.

另請參閱 value ().

const T &const_iterator:: value () const

Returns the current item's value.

另請參閱 key () 和 operator* ().

const T &const_iterator:: operator* () const

Returns the current item's value.

如同 value ().

另請參閱 key ().

const_iterator &const_iterator:: operator++ ()

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

Calling this function on QMultiMap::end () leads to undefined results.

另請參閱 operator-- ().

const_iterator const_iterator:: operator++ ( int )

這是重載函數。

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

const_iterator &const_iterator:: operator-- ()

The prefix -- operator ( --i ) makes the preceding item current and returns an iterator pointing to the new current item.

Calling this function on QMultiMap::begin () leads to undefined results.

另請參閱 operator++ ().

const_iterator const_iterator:: operator-- ( int )

這是重載函數。

The postfix -- operator ( i-- ) makes the preceding item current and returns an iterator pointing to the previously current item.

const T *const_iterator:: operator-> () const

Returns a pointer to the current item's value.

另請參閱 value ().

相關非成員

bool operator== (const const_iterator & lhs , const const_iterator & rhs )

返迴 true if lhs points to the same item as the rhs iterator; otherwise returns false .

另請參閱 operator!= ().

bool operator!= (const const_iterator & lhs , const const_iterator & rhs )

返迴 true if lhs points to a different item than the rhs iterator; otherwise returns false .

另請參閱 operator== ().

內容

1. 公共類型

2. 公共函數

3. 相關非成員

4. 詳細描述