内容

• 公共函数
• 详细描述

QMutableHashIterator 类

The QMutableHashIterator class provides a Java-style non-const iterator for QHash and QMultiHash . 更多...

头：	#include <QMutableHashIterator>
qmake:	QT += core

• 所有成员列表，包括继承成员

公共函数

	QMutableHashIterator (QHash<Key, T> & hash )
bool	findNext (const T & value )
bool	findPrevious (const T & value )
bool	hasNext () const
bool	hasPrevious () const
const Key &	key () const
QMutableHashIterator::Item	next ()
QMutableHashIterator::Item	peekNext () const
QMutableHashIterator::Item	peekPrevious () const
QMutableHashIterator::Item	previous ()
void	remove ()
void	setValue (const T & value )
void	toBack ()
void	toFront ()
const T &	value () const
T &	value ()
QMutableHashIterator<Key, T> &	operator= (QHash<Key, T> & container )

详细描述

The QMutableHashIterator class provides a Java-style non-const iterator for QHash and QMultiHash .

QHash 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.

QMutableHashIterator <Key, T> allows you to iterate over a QHash (or a QMultiHash ) and modify the hash. If you don't want to modify the hash (or have a const QHash ), use the slightly faster QHashIterator 代替。

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

QHash<int, QWidget *> hash;
...
QMutableHashIterator<QString, QWidget *> i(hash);
while (i.hasNext()) {
    i.next();
    qDebug() << i.key() << ": " << i.value();
}
					

The next () function returns the next item in the hash 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:

QMutableHashIterator<int, QWidget *> i(hash);
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:

QMutableHashIterator<int, QWidget *> i(hash);
while (i.findNext(widget)) {
    qDebug() << "Found widget " << widget << " under key "
             << i.key();
}
					

If you want to remove items as you iterate over the hash, use remove (). If you want to modify the value of an item, use setValue ().

范例：

QMutableHashIterator<QString, QString> i(hash);
while (i.hasNext()) {
    i.next();
    if (i.key() == i.value())
        i.remove();
}
					

The example removes all (key, value) pairs where the key and the value are the same.

Only one mutable iterator can be active on a given hash at any time. Furthermore, no changes should be done directly to the hash 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 QHashIterator and QHash::iterator .

成员函数文档编制

void QMutableHashIterator:: setValue (const T & value )

Replaces the value of the last item that was jumped over using one of the traversal functions with value .

The traversal functions are next (), previous (), findNext ()，和 findPrevious ().

另请参阅 key (), value ()，和 remove ().

void QMutableHashIterator:: remove ()

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

另请参阅 setValue ().

bool QMutableHashIterator:: 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 ().

bool QMutableHashIterator:: 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 ().

const Key &QMutableHashIterator:: 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 ().

T &QMutableHashIterator:: value ()

这是重载函数。

Returns a non-const reference to the value of the last item that was jumped over using one of the traversal functions.

const T &QMutableHashIterator:: 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 () 和 setValue ().

QMutableHashIterator::Item QMutableHashIterator:: 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 ().

QMutableHashIterator::Item QMutableHashIterator:: 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 ().

bool QMutableHashIterator:: 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 ().

QMutableHashIterator::Item QMutableHashIterator:: peekNext () const

Returns a reference to 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 ().

QMutableHashIterator::Item QMutableHashIterator:: 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 ().

bool QMutableHashIterator:: 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 QMutableHashIterator:: toBack ()

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

另请参阅 toFront () 和 previous ().

void QMutableHashIterator:: toFront ()

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

另请参阅 toBack () 和 next ().

QMutableHashIterator < Key , T > &QMutableHashIterator:: operator= ( QHash < Key , T > & container )

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

另请参阅 toFront () 和 toBack ().

QMutableHashIterator:: QMutableHashIterator ( QHash < Key , T > & hash )

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

另请参阅 operator= ().