iterator Class Reference(QList::iterator)The QList::iterator class provides an STL-style non-const iterator for QList and QQueue. Далее... #include <QList>
Открытые типы
Открытые функции
Подробное описаниеThe QList::iterator class provides an STL-style non-const iterator for QList and QQueue. QList features both STL-style iterators and Java-style iterators. The STL-style iterators are more low-level and more cumbersome to use; on the other hand, they are slightly faster and, for developers who already know STL, have the advantage of familiarity. QList<T>::iterator allows you to iterate over a QList<T> (or QQueue<T>) and to modify the list item associated with the iterator. If you want to iterate over a const QList, use QList::const_iterator instead. It is generally good practice to use QList::const_iterator on a non-const QList as well, unless you need to change the QList through the iterator. Const iterators are slightly faster, and can improve code readability. The default QList::iterator constructor creates an uninitialized iterator. You must initialize it using a QList function like QList::begin(), QList::end(), or QList::insert() before you can start iterating. Here's a typical loop that prints all the items stored in a list: QList<QString> list; list.append("January"); list.append("February"); ... list.append("December"); QList<QString>::iterator i; for (i = list.begin(); i != list.end(); ++i) cout << *i << endl; Let's see a few examples of things we can do with a QList::iterator that we cannot do with a QList::const_iterator. Here's an example that increments every value stored in a QList<int> by 2: QList<int>::iterator i; for (i = list.begin(); i != list.end(); ++i) *i += 2; Most QList functions accept an integer index rather than an iterator. For that reason, iterators are rarely useful in connection with QList. One place where STL-style iterators do make sense is as arguments to generic algorithms. For example, here's how to delete all the widgets stored in a QList<QWidget *>: QList<QWidget *> list; ... qDeleteAll(list.begin(), list.end()); Multiple iterators can be used on the same list. However, be aware that any non-const function call performed on the QList will render all existing iterators undefined. If you need to keep iterators over a long period of time, we recommend that you use QLinkedList rather than QList. See also QList::const_iterator and QMutableListIterator. Описание типов-членовtypedef iterator::iterator_categoryA synonym for std::random_access_iterator_tag indicating this iterator is a random access iterator. Описание функций-членовiterator::iterator ()Constructs an uninitialized iterator. Functions like operator*() and operator++() should not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it. See also QList::begin() and QList::end(). iterator::iterator ( const iterator & other )Создаёт копию other. bool iterator::operator!= ( const iterator & other ) constReturns true if other points to a different item than this iterator; otherwise returns false. Смотрите также operator==(). bool iterator::operator!= ( const const_iterator & other ) constReturns true if other points to a different item than this iterator; otherwise returns false. Смотрите также operator==(). T & iterator::operator* () constReturns a modifiable reference to the current item. You can change the value of an item by using operator*() on the left side of an assignment, for example: if (*it == "Hello") *it = "Bonjour"; See also operator->(). iterator iterator::operator+ ( int j ) constReturns an iterator to the item at j positions forward from this iterator. (If j is negative, the iterator goes backward.) See also operator-() and operator+=(). iterator & iterator::operator++ ()The prefix ++ operator (++it) advances the iterator to the next item in the list and returns an iterator to the new current item. Calling this function on QList::end() leads to undefined results. See also operator--(). iterator iterator::operator++ ( int )Это перегруженная функция. The postfix ++ operator (it++) advances the iterator to the next item in the list and returns an iterator to the previously current item. iterator & iterator::operator+= ( int j )Advances the iterator by j items. (If j is negative, the iterator goes backward.) See also operator-=() and operator+(). iterator iterator::operator- ( int j ) constReturns an iterator to the item at j positions backward from this iterator. (If j is negative, the iterator goes forward.) See also operator+() and operator-=(). int iterator::operator- ( iterator other ) constReturns the number of items between the item pointed to by other and the item pointed to by this iterator. iterator & iterator::operator-- ()The prefix -- operator (--it) makes the preceding item current and returns an iterator to the new current item. Calling this function on QList::begin() leads to undefined results. See also operator++(). iterator iterator::operator-- ( int )Это перегруженная функция. The postfix -- operator (it--) makes the preceding item current and returns an iterator to the previously current item. iterator & iterator::operator-= ( int j )Makes the iterator go back by j items. (If j is negative, the iterator goes forward.) See also operator+=() and operator-(). T * iterator::operator-> () constReturns a pointer to the current item. See also operator*(). bool iterator::operator< ( const iterator & other ) constReturns true if the item pointed to by this iterator is less than the item pointed to by the other iterator. bool iterator::operator< ( const const_iterator & other ) constReturns true if the item pointed to by this iterator is less than the item pointed to by the other iterator. bool iterator::operator<= ( const iterator & other ) constReturns true if the item pointed to by this iterator is less than or equal to the item pointed to by the other iterator. bool iterator::operator<= ( const const_iterator & other ) constReturns true if the item pointed to by this iterator is less than or equal to the item pointed to by the other iterator. bool iterator::operator== ( const iterator & other ) constReturns true if other points to the same item as this iterator; otherwise returns false. Смотрите также operator!=(). bool iterator::operator== ( const const_iterator & other ) constReturns true if other points to the same item as this iterator; otherwise returns false. Смотрите также operator!=(). bool iterator::operator> ( const iterator & other ) constReturns true if the item pointed to by this iterator is greater than the item pointed to by the other iterator. bool iterator::operator> ( const const_iterator & other ) constReturns true if the item pointed to by this iterator is greater than the item pointed to by the other iterator. bool iterator::operator>= ( const iterator & other ) constReturns true if the item pointed to by this iterator is greater than or equal to the item pointed to by the other iterator. bool iterator::operator>= ( const const_iterator & other ) constReturns true if the item pointed to by this iterator is greater than or equal to the item pointed to by the other iterator. T & iterator::operator[] ( int j ) constReturns a modifiable reference to the item at position *this + j. This function is provided to make QList iterators behave like C++ pointers. See also operator+(). |
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