The QMap::const_iterator 類提供 STL 樣式 const 迭代器為 QMap . 更多...
| iterator_category |
| 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 |
| bool | operator!= (const const_iterator & lhs , const const_iterator & rhs ) |
| bool | operator== (const const_iterator & lhs , const const_iterator & rhs ) |
QMap <Key, T>::const_iterator allows you to iterate over a QMap . If you want to modify the QMap as you iterate over it, you must use QMap::iterator instead. It is generally good practice to use QMap::const_iterator on a non-const QMap as well, unless you need to change the QMap through the iterator. Const iterators are slightly faster, and can improve code readability.
默認 QMap::const_iterator constructor creates an uninitialized iterator. You must initialize it using a QMap function like QMap::cbegin (), QMap::cend ()，或 QMap::constFind () before you can start iterating. Here's a typical loop that prints all the (key, value) pairs stored in a map:
QMap<QString, int> map; map.insert("January", 1); map.insert("February", 2); ... map.insert("December", 12); for (auto i = map.cbegin(), end = map.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:
QMap<QString, int>::const_iterator i = map.cbegin(); while (i != map.cend()) { if (i.value() > 10) i = map.erase(i); else ++i; }
And here the same behavior with erase_if ()
erase_if(map, [](const QMap<QString, int>::iterator it) { return it.value() > 10; });
不像 QHash , which stores its items in an arbitrary order, QMap stores its items ordered by key.
Multiple iterators can be used on the same 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 QMap::iterator , QMap::key_iterator ，和 QMap::const_key_value_iterator .
[alias]
const_iterator::
iterator_category
同義詞 std::bidirectional_iterator_tag indicating this iterator is a bidirectional 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 QMap::constBegin () 和 QMap::constEnd ().
構造副本為 other .
Returns the current item's key.
另請參閱 value ().
Returns the current item's value.
Returns the current item's value.
如同 value ().
另請參閱 key ().
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 QMap::end () leads to undefined results.
另請參閱 operator-- ().
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.
The prefix
--
operator (
--i
) makes the preceding item current and returns an iterator pointing to the new current item.
Calling this function on QMap::begin () leads to undefined results.
另請參閱 operator++ ().
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.
Returns a pointer to the current item's value.
另請參閱 value ().
返迴
true
if
lhs
points to the same item as the
rhs
iterator; otherwise returns
false
.
另請參閱 operator!= ().
返迴
true
if
lhs
points to a different item than the
rhs
iterator; otherwise returns
false
.
另請參閱 operator== ().