QMapIterator class provides a Java-style const iterator for QMap and QMultiMap . 更多...
| 头： | #include <QMapIterator> |
| qmake: | QT += core |
| QMapIterator (const QMap<Key, T> & map ) | |
| bool | findNext (const T & value ) |
| bool | findPrevious (const T & value ) |
| bool | hasNext () const |
| bool | hasPrevious () const |
| const Key & | key () const |
| Item | next () |
| Item | peekNext () const |
| Item | peekPrevious () const |
| Item | 上一 () |
| void | toBack () |
| void | toFront () |
| const T & | value () const |
| QMapIterator & | operator= (const QMap<Key, T> & map ) |
QMapIterator class provides a Java-style const iterator for QMap and QMultiMap .
QMap 同时拥有 Java 样式迭代器 and STL 样式迭代器 . The Java-style iterators are more high-level and easier to use than the STL-style iterators; on the other hand, they are slightly less efficient.
QMapIterator <Key, T> allows you to iterate over a QMap (or a QMultiMap ). If you want to modify the map as you iterate over it, use QMutableMapIterator 代替。
QMapIterator constructor takes a QMap as argument. After construction, the iterator is located at the very beginning of the map (before the first item). Here's how to iterate over all the elements sequentially:
QMap<int, QWidget *> map; ... QMapIterator<int, QWidget *> i(map); while (i.hasNext()) { i.next(); qDebug() << i.key() << ": " << i.value(); }
next () function returns the next item in the map and advances the iterator. The key () 和 value () functions return the key and value of the last item that was jumped over.
Unlike STL-style iterators, Java-style iterators point between items rather than directly at items. The first call to next () advances the iterator to the position between the first and second item, and returns the first item; the second call to next () advances the iterator to the position between the second and third item; and so on.
Here's how to iterate over the elements in reverse order:
QMapIterator<int, QWidget *> i(map); i.toBack(); while (i.hasPrevious()) { i.previous(); qDebug() << i.key() << ": " << i.value(); }
If you want to find all occurrences of a particular value, use findNext () 或 findPrevious () in a loop. For example:
QMapIterator<int, QWidget *> i(map); while (i.findNext(widget)) { qDebug() << "Found widget " << widget << " under key " << i.key(); }
Multiple iterators can be used on the same map. If the map is modified while a QMapIterator is active, the QMapIterator will continue iterating over the original map, ignoring the modified copy.
另请参阅 QMutableMapIterator and QMap::const_iterator .
构造迭代器为遍历 map . The iterator is set to be at the front of the map (before the first item).
另请参阅 operator= ().
搜索
value
starting from the current iterator position forward. Returns
true
if a (key, value) pair with value
value
is found; otherwise returns
false
.
After the call, if value was found, the iterator is positioned just after the matching item; otherwise, the iterator is positioned at the back of the container.
另请参阅 findPrevious ().
搜索
value
starting from the current iterator position backward. Returns
true
if a (key, value) pair with value
value
is found; otherwise returns
false
.
After the call, if value was found, the iterator is positioned just before the matching item; otherwise, the iterator is positioned at the front of the container.
另请参阅 findNext ().
返回
true
if there is at least one item ahead of the iterator, i.e. the iterator is
not
at the back of the container; otherwise returns
false
.
另请参阅 hasPrevious () 和 next ().
返回
true
if there is at least one item behind the iterator, i.e. the iterator is
not
at the front of the container; otherwise returns
false
.
Returns the key of the last item that was jumped over using one of the traversal functions ( next (), 上一 (), findNext (), findPrevious ()).
After a call to next () 或 findNext (), key() is equivalent to peekPrevious ().key(). After a call to 上一 () 或 findPrevious (), key() is equivalent to peekNext ().key().
另请参阅 value ().
Returns the next item and advances the iterator by one position.
调用 key () on the return value to obtain the item's key, and value () to obtain the value.
Calling this function on an iterator located at the back of the container leads to undefined results.
另请参阅 hasNext (), peekNext ()，和 上一 ().
Returns the next item without moving the iterator.
调用 key () on the return value to obtain the item's key, and value () to obtain the value.
Calling this function on an iterator located at the back of the container leads to undefined results.
另请参阅 hasNext (), next ()，和 peekPrevious ().
Returns the previous item without moving the iterator.
调用 key () on the return value to obtain the item's key, and value () to obtain the value.
Calling this function on an iterator located at the front of the container leads to undefined results.
另请参阅 hasPrevious (), 上一 ()，和 peekNext ().
Returns the previous item and moves the iterator back by one position.
调用 key () on the return value to obtain the item's key, and value () to obtain the value.
Calling this function on an iterator located at the front of the container leads to undefined results.
另请参阅 hasPrevious (), peekPrevious ()，和 next ().
Moves the iterator to the back of the container (after the last item).
Moves the iterator to the front of the container (before the first item).
Returns the value of the last item that was jumped over using one of the traversal functions ( next (), 上一 (), findNext (), findPrevious ()).
After a call to next () 或 findNext (), value() is equivalent to peekPrevious ().value(). After a call to 上一 () 或 findPrevious (), value() is equivalent to peekNext ().value().
另请参阅 key ().
Makes the iterator operate on map . The iterator is set to be at the front of the map (before the first item).
