QMutableSetIterator 类

template <typename T> class QMutableSetIterator

QMutableSetIterator 类提供 Java 样式非常量迭代器为 QSet . 更多...

头：	#include <QMutableSetIterator>
qmake:	QT += core
Since:	Qt 4.2

该类在 Qt 4.2 引入。

公共函数

	QMutableSetIterator (QSet<T> & set )
QMutableSetIterator<T> &	operator= (QSet<T> & container )
bool	findPrevious (const T & value )
bool	hasNext () const
const T &	next ()
const T &	peekNext () const
void	remove ()
void	toBack ()
void	toFront ()
const T &	value () const

详细描述

QSet 同时拥有 Java 风格迭代器 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.

QMutableSetIterator<T> allows you to iterate over a QSet <T> and remove items from the set as you iterate. If you don't want to modify the set (or have a const QSet ), use the slightly faster QSetIterator <T> 代替。

The QMutableSetIterator constructor takes a QSet as argument. After construction, the iterator is located at the very beginning of the set (before the first item). Here's how to iterate over all the elements sequentially:

QSet<float> set;
...
QMutableSetIterator<float> i(set);
while (i.hasNext())
    float f = i.next();

The next () function returns the next item in the set and advances the iterator. 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, returning the second item; and so on.

Here's how to iterate over the elements in reverse order:

QMutableSetIterator<float> i(set);
i.toBack();
while (i.hasPrevious())
    float f = i.previous();

If you want to remove items as you iterate over the set, use remove ().

Only one mutable iterator can be active on a given set at any time. Furthermore, no changes should be done directly to the set while the iterator is active (as opposed to through the iterator), since this could invalidate the iterator and lead to undefined behavior.

另请参阅 QSetIterator and QSet::iterator .

成员函数文档编制

const T &QMutableSetIterator:: 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 () or findNext(), value () is equivalent to peekPrevious(). After a call to previous() or findPrevious (), value () is equivalent to peekNext ().

bool QMutableSetIterator:: findPrevious (const T & value )

搜索 value starting from the current iterator position backward. Returns true if 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 ().

const T &QMutableSetIterator:: peekNext () const

Returns the next item without moving the iterator.

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 ().

const T &QMutableSetIterator:: next ()

Returns the next item and advances the iterator by one position.

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 ().

bool QMutableSetIterator:: 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 ().

void QMutableSetIterator:: toBack ()

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

另请参阅 toFront () 和 previous ().

void QMutableSetIterator:: toFront ()

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

另请参阅 toBack () 和 next ().

QMutableSetIterator < T > &QMutableSetIterator:: operator= ( QSet < T > & container )

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

另请参阅 toFront () 和 toBack ().

QMutableSetIterator:: QMutableSetIterator ( QSet < T > & set )

构造迭代器为遍历 set . The iterator is set to be at the front of the set (before the first item).

另请参阅 operator= ().

void QMutableSetIterator:: remove ()

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

范例：

QMutableSetIterator<int> i(set);
while (i.hasNext()) {
    int val = i.next();
    if (val < -32768 || val > 32767)
        i.remove();
}

另请参阅 value ().