QMapIterator 类

template <typename Key, typename T> class QMapIterator

QMapIterator 类提供 Java 样式常量迭代器为 QMap . 更多...

头：	#include <QMapIterator>
CMake:	find_package(Qt6 REQUIRED COMPONENTS Core) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake:	QT += core

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公共函数

	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
QMapIterator<Key, T>::Item	next ()
QMapIterator<Key, T>::Item	peekNext () const
QMapIterator<Key, T>::Item	peekPrevious () const
QMapIterator<Key, T>::Item	previous ()
void	toBack ()
void	toFront ()
const T &	value () const
QMapIterator<Key, T> &	operator= (const QMap<Key, T> & container )

详细描述

QMap 同时拥有 Java 风格迭代器 and STL 样式迭代器。STL 样式迭代器效率更高且应首选。

QMapIterator<Key, T> allows you to iterate over a QMap . If you want to modify the map as you iterate over it, use QMutableMapIterator 代替。

The 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();
}

The 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 .

成员函数文档编制

QMapIterator:: QMapIterator (const QMap < Key , T > & map )

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= ().

QMapIterator < Key , T > &QMapIterator:: operator= (const QMap < Key , T > & container )

Makes the iterator operate on map . The iterator is set to be at the front of the map (before the first item).

另请参阅 toFront () 和 toBack ().

void QMapIterator:: toFront ()

Moves the iterator to the front of the container (before the first item).

另请参阅 toBack () 和 next ().

void QMapIterator:: toBack ()

Moves the iterator to the back of the container (after the last item).

另请参阅 toFront () 和 previous ().

bool QMapIterator:: hasNext () const

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 ().

QMapIterator < Key , T > ::Item QMapIterator:: next ()

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 previous ().

QMapIterator < Key , T > ::Item QMapIterator:: peekNext () const

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 ().

bool QMapIterator:: hasPrevious () const

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 .

另请参阅 hasNext () 和 previous ().

QMapIterator < Key , T > ::Item QMapIterator:: previous ()

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 ().

QMapIterator < Key , T > ::Item QMapIterator:: peekPrevious () const

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 (), previous ()，和 peekNext ().

const T &QMapIterator:: value () const

Returns the value of the last item that was jumped over using one of the traversal functions ( next (), previous (), findNext (), findPrevious ()).

After a call to next () 或 findNext (), value () is equivalent to peekPrevious (). value (). After a call to previous () 或 findPrevious (), value () is equivalent to peekNext (). value ().

另请参阅 key ().

const Key &QMapIterator:: key () const

Returns the key of the last item that was jumped over using one of the traversal functions ( next (), previous (), findNext (), findPrevious ()).

After a call to next () 或 findNext (), key () is equivalent to peekPrevious (). key (). After a call to previous () 或 findPrevious (), key () is equivalent to peekNext (). key ().

另请参阅 value ().

bool QMapIterator:: findNext (const T & value )

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 ().

bool QMapIterator:: findPrevious (const T & value )

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 ().