The QMutableListIterator class provides a Java-style non-const iterator for QList and QQueue . 更多...
| 头： | #include <QMutableListIterator> |
| qmake: | QT += core |
| QMutableListIterator (QList<T> & list ) | |
| 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 () |
| QMutableListIterator<T> & | operator= (QList<T> & container ) |
The QMutableListIterator class provides a Java-style non-const iterator for QList and QQueue .
QList 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 QList member functions take an index as their first parameter, making it possible to access, insert, and remove items without using iterators.
QMutableListIterator <T> allows you to iterate over a QList <T> (or a QQueue <T>) and modify the list. If you don't want to modify the list (or have a const QList ), use the slightly faster QListIterator <T> 代替。
The QMutableListIterator constructor takes a QList 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:
QList<float> list; ... QMutableListIterator<float> i(list); while (i.hasNext()) qDebug() << i.next();
The next () function returns the next item in the list 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:
QMutableListIterator<float> i(list); i.toBack(); while (i.hasPrevious()) qDebug() << 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 list, use remove (). If you want to modify the value of an item, use setValue (). If you want to insert a new item in the list, use insert ().
范例：
QMutableListIterator<int> i(list); while (i.hasNext()) { int val = i.next(); if (val < 0) { i.setValue(-val); } else if (val == 0) { i.remove(); } }
The example traverses a list, replacing negative numbers with their absolute values, and eliminating zeroes.
Only one mutable iterator can be active on a given list at any time. Furthermore, no changes should be done directly to the list 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 QListIterator and QList::iterator .
插入 value at the current iterator position. After the call, the iterator is located just after the inserted item.
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.
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 ().
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 ().
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 ().
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 ().
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 ().
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 ().
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 ().
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 ().
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 ().
Moves the iterator to the back of the container (after the last item).
另请参阅 toFront () 和 previous ().
Moves the iterator to the front of the container (before the first item).
Makes the iterator operate on list . The iterator is set to be at the front of the list (before the first item).
构造迭代器为遍历 list . The iterator is set to be at the front of the list (before the first item).
另请参阅 operator= ().
Removes the last item that was jumped over using one of the traversal functions ( next (), previous (), findNext (), findPrevious ()).
范例：
QMutableListIterator<int> i(list); while (i.hasNext()) { int val = i.next(); if (val < -32768 || val > 32767) i.remove(); }
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：
QMutableListIterator<double> i(list); while (i.hasNext()) { double val = i.next(); i.setValue(std::sqrt(val)); }
