QMutableVectorIterator Class

template <typename T> class QMutableVectorIterator

The QMutableVectorIterator class provides a Java-style non-const iterator for QVector and QStack . 更多...

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

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公共函数

	QMutableVectorIterator (QVector<T> & vector )
QMutableVectorIterator<T> &	operator= (QVector<T> & container )
bool	findNext (const T & value )
bool	findPrevious (const T & value )
bool	hasNext () const
bool	hasPrevious () const
void	insert (const T & value )
T &	next ()
T &	peekNext () const
T &	peekPrevious () const
T &	previous ()
void	remove ()
void	setValue (const T & value ) const
void	toBack ()
void	toFront ()
const T &	value () const
T &	value ()

详细描述

QVector 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.

An alternative to using iterators is to use index positions. Most QVector member functions take an index as their first parameter, making it possible to access, insert, and remove items without using iterators.

QMutableVectorIterator<T> allows you to iterate over a QVector <T> and modify the vector. If you don't want to modify the vector (or have a const QVector ), use the slightly faster QVectorIterator <T> 代替。

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

QVector<float> vector;
...
QMutableVectorIterator<float> i(vector);
while (i.hasNext())
    float f = i.next();

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

QMutableVectorIterator<float> i(vector);
i.toBack();
while (i.hasPrevious())
    float f = i.previous();

If you want to find all occurrences of a particular value, use findNext () 或 findPrevious () in a loop.

If you want to remove items as you iterate over the vector, use remove (). If you want to modify the value of an item, use setValue (). If you want to insert a new item in the vector, use insert ().

范例：

QMutableVectorIterator<int> i(vector);
while (i.hasNext()) {
    int val = i.next();
    if (val < 0) {
        i.setValue(-val);
    } else if (val == 0) {
        i.remove();
    }
}

The example traverses a vector, replacing negative numbers with their absolute values, and eliminating zeroes.

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

成员函数文档编制

void QMutableVectorIterator:: insert (const T & value )

插入 value at the current iterator position. After the call, the iterator is located just after the inserted item.

另请参阅 remove () 和 setValue ().

T &QMutableVectorIterator:: 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 &QMutableVectorIterator:: 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 (). After a call to previous () 或 findPrevious (), value () is equivalent to peekNext ().

bool QMutableVectorIterator:: 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 ().

bool QMutableVectorIterator:: findNext (const T & value )

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

T &QMutableVectorIterator:: peekPrevious () const

Returns a reference to the previous item, without moving the iterator.

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 ().

T &QMutableVectorIterator:: previous ()

Returns a reference to the previous item and moves the iterator back by one position.

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 QMutableVectorIterator:: 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 ().

T &QMutableVectorIterator:: peekNext () const

Returns a reference to 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 ().

T &QMutableVectorIterator:: next ()

Returns a reference to 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 QMutableVectorIterator:: 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 QMutableVectorIterator:: toBack ()

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

另请参阅 toFront () 和 previous ().

void QMutableVectorIterator:: toFront ()

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

另请参阅 toBack () 和 next ().

QMutableVectorIterator < T > &QMutableVectorIterator:: operator= ( QVector < T > & container )

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

另请参阅 toFront () 和 toBack ().

QMutableVectorIterator:: QMutableVectorIterator ( QVector < T > & vector )

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

另请参阅 operator= ().

void QMutableVectorIterator:: remove ()

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

范例：

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

另请参阅 insert () 和 setValue ().

void QMutableVectorIterator:: setValue (const T & value ) const

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 ().

范例：

QMutableVectorIterator<double> i(list);
while (i.hasNext()) {
    double val = i.next();
    i.setValue(std::sqrt(val));
}

另请参阅 value (), remove ()，和 insert ().