Qt 4.8
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QList< T >::const_iterator Class Reference

The QList::const_iterator class provides an STL-style const iterator for QList and QQueue. More...

#include <qlist.h>

Public Types

typedef qptrdiff difference_type
 
typedef std::random_access_iterator_tag iterator_category
 A synonym for {std::random_access_iterator_tag} indicating this iterator is a random access iterator. More...
 
typedef const T * pointer
 
typedef const T & reference
 
typedef T value_type
 

Public Functions

 const_iterator ()
 Constructs an uninitialized iterator. More...
 
 const_iterator (Node *n)
 
 const_iterator (const const_iterator &o)
 Constructs a copy of other. More...
 
 const_iterator (const iterator &o)
 Constructs a copy of other. More...
 
bool operator!= (const const_iterator &o) const
 Returns true if other points to a different item than this iterator; otherwise returns false. More...
 
const T & operator* () const
 Returns the current item. More...
 
const_iterator operator+ (int j) const
 Returns an iterator to the item at j positions forward from this iterator. More...
 
const_iteratoroperator++ ()
 The prefix ++ operator (++it) advances the iterator to the next item in the list and returns an iterator to the new current item. More...
 
const_iterator operator++ (int)
 The postfix ++ operator (it++) advances the iterator to the next item in the list and returns an iterator to the previously current item. More...
 
const_iteratoroperator+= (int j)
 Advances the iterator by j items. More...
 
const_iterator operator- (int j) const
 Returns an iterator to the item at j positions backward from this iterator. More...
 
int operator- (const_iterator j) const
 Returns the number of items between the item pointed to by other and the item pointed to by this iterator. More...
 
const_iteratoroperator-- ()
 The prefix – operator (–it) makes the preceding item current and returns an iterator to the new current item. More...
 
const_iterator operator-- (int)
 The postfix – operator (it–) makes the preceding item current and returns an iterator to the previously current item. More...
 
const_iteratoroperator-= (int j)
 Makes the iterator go back by j items. More...
 
const T * operator-> () const
 Returns a pointer to the current item. More...
 
bool operator< (const const_iterator &other) const
 Returns true if the item pointed to by this iterator is less than the item pointed to by the other iterator. More...
 
bool operator<= (const const_iterator &other) const
 Returns true if the item pointed to by this iterator is less than or equal to the item pointed to by the other iterator. More...
 
bool operator== (const const_iterator &o) const
 Returns true if other points to the same item as this iterator; otherwise returns false. More...
 
bool operator> (const const_iterator &other) const
 Returns true if the item pointed to by this iterator is greater than the item pointed to by the other iterator. More...
 
bool operator>= (const const_iterator &other) const
 Returns true if the item pointed to by this iterator is greater than or equal to the item pointed to by the other iterator. More...
 
const T & operator[] (int j) const
 Returns the item at position *this + {j}. More...
 

Public Variables

Nodei
 

Detailed Description

template<typename T>
class QList< T >::const_iterator

The QList::const_iterator class provides an STL-style const iterator for QList and QQueue.

QList provides 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>::const_iterator allows you to iterate over a QList<T> (or a QQueue<T>). If you want to modify the QList as you iterate over it, use QList::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::const_iterator constructor creates an uninitialized iterator. You must initialize it using a QList function like QList::constBegin(), QList::constEnd(), or QList::insert() before you can start iterating. Here's a typical loop that prints all the items stored in a list:

list.append("January");
list.append("February");
...
list.append("December");
for (i = list.constBegin(); i != list.constEnd(); ++i)
cout << *i << endl;

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 *>:

...
qDeleteAll(list.constBegin(), list.constEnd());

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::iterator, QListIterator

Definition at line 228 of file qlist.h.

Typedefs

◆ difference_type

template<typename T>
QList< T >::const_iterator::difference_type
Warning
This function is not part of the public interface.

Definition at line 232 of file qlist.h.

◆ iterator_category

template<typename T>
QList< T >::const_iterator::iterator_category

A synonym for {std::random_access_iterator_tag} indicating this iterator is a random access iterator.

Definition at line 231 of file qlist.h.

◆ pointer

template<typename T>
QList< T >::const_iterator::pointer
Warning
This function is not part of the public interface.

Definition at line 234 of file qlist.h.

◆ reference

template<typename T>
QList< T >::const_iterator::reference
Warning
This function is not part of the public interface.

Definition at line 235 of file qlist.h.

◆ value_type

template<typename T>
QList< T >::const_iterator::value_type
Warning
This function is not part of the public interface.

Definition at line 233 of file qlist.h.

Constructors and Destructors

◆ const_iterator() [1/4]

template<typename T>
QList< T >::const_iterator::const_iterator ( )
inline

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::constBegin() QList::constEnd()

Definition at line 237 of file qlist.h.

237 : i(0) {}

◆ const_iterator() [2/4]

template<typename T>
QList< T >::const_iterator::const_iterator ( Node node)
inline
Warning
This function is not part of the public interface.

Definition at line 238 of file qlist.h.

238 : i(n) {}

◆ const_iterator() [3/4]

template<typename T>
QList< T >::const_iterator::const_iterator ( const const_iterator o)
inline

Constructs a copy of other.

Definition at line 239 of file qlist.h.

239 : i(o.i) {}

◆ const_iterator() [4/4]

template<typename T>
QList< T >::const_iterator::const_iterator ( const iterator o)
inline

Constructs a copy of other.

Definition at line 243 of file qlist.h.

243 : i(o.i) {}

Functions

◆ operator!=()

template<typename T>
bool QList< T >::const_iterator::operator!= ( const const_iterator other) const
inline

Returns true if other points to a different item than this iterator; otherwise returns false.

See also
operator==()

Definition at line 249 of file qlist.h.

249 { return i != o.i; }

◆ operator*()

template<typename T>
const T & QList< T >::const_iterator::operator* ( ) const
inline

Returns the current item.

See also
operator->()

Definition at line 245 of file qlist.h.

245 { return i->t(); }
Q_INLINE_TEMPLATE T & t()
Definition: qlist.h:112

◆ operator+()

template<typename T>
QList::const_iterator QList< T >::const_iterator::operator+ ( int  j) const
inline

Returns an iterator to the item at j positions forward from this iterator.

(If j is negative, the iterator goes backward.)

See also
operator-(), operator+=()

Definition at line 260 of file qlist.h.

260 { return const_iterator(i+j); }
const_iterator()
Constructs an uninitialized iterator.
Definition: qlist.h:237

◆ operator++() [1/2]

template<typename T>
QList::const_iterator & QList< T >::const_iterator::operator++ ( )
inline

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--()

Definition at line 254 of file qlist.h.

254 { ++i; return *this; }

◆ operator++() [2/2]

template<typename T>
QList::const_iterator QList< T >::const_iterator::operator++ ( int  )
inline

The postfix ++ operator (it++) advances the iterator to the next item in the list and returns an iterator to the previously current item.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Definition at line 255 of file qlist.h.

255 { Node *n = i; ++i; return n; }

◆ operator+=()

template<typename T>
QList::const_iterator & QList< T >::const_iterator::operator+= ( int  j)
inline

Advances the iterator by j items.

(If j is negative, the iterator goes backward.)

See also
operator-=(), operator+()

Definition at line 258 of file qlist.h.

258 { i+=j; return *this; }

◆ operator-() [1/2]

template<typename T>
QList::const_iterator QList< T >::const_iterator::operator- ( int  j) const
inline

Returns an iterator to the item at j positions backward from this iterator.

(If j is negative, the iterator goes forward.)

See also
operator+(), operator-=()

Definition at line 261 of file qlist.h.

261 { return const_iterator(i-j); }
const_iterator()
Constructs an uninitialized iterator.
Definition: qlist.h:237

◆ operator-() [2/2]

template<typename T>
int QList< T >::const_iterator::operator- ( const_iterator  j) const
inline

Returns the number of items between the item pointed to by other and the item pointed to by this iterator.

Definition at line 262 of file qlist.h.

262 { return i - j.i; }

◆ operator--() [1/2]

template<typename T>
QList::const_iterator & QList< T >::const_iterator::operator-- ( )
inline

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++()

Definition at line 256 of file qlist.h.

256 { i--; return *this; }

◆ operator--() [2/2]

template<typename T>
QList::const_iterator QList< T >::const_iterator::operator-- ( int  )
inline

The postfix – operator (it–) makes the preceding item current and returns an iterator to the previously current item.

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Definition at line 257 of file qlist.h.

257 { Node *n = i; i--; return n; }

◆ operator-=()

template<typename T>
QList::const_iterator & QList< T >::const_iterator::operator-= ( int  j)
inline

Makes the iterator go back by j items.

(If j is negative, the iterator goes forward.)

See also
operator+=(), operator-()

Definition at line 259 of file qlist.h.

259 { i-=j; return *this; }

◆ operator->()

template<typename T>
const T * QList< T >::const_iterator::operator-> ( ) const
inline

Returns a pointer to the current item.

See also
operator*()

Definition at line 246 of file qlist.h.

246 { return &i->t(); }
Q_INLINE_TEMPLATE T & t()
Definition: qlist.h:112

◆ operator<()

template<typename T>
bool QList< T >::const_iterator::operator< ( const const_iterator other) const
inline

Returns true if the item pointed to by this iterator is less than the item pointed to by the other iterator.

Definition at line 250 of file qlist.h.

250 { return i < other.i; }

◆ operator<=()

template<typename T>
bool QList< T >::const_iterator::operator<= ( const const_iterator other) const
inline

Returns true if the item pointed to by this iterator is less than or equal to the item pointed to by the other iterator.

Definition at line 251 of file qlist.h.

251 { return i <= other.i; }

◆ operator==()

template<typename T>
bool QList< T >::const_iterator::operator== ( const const_iterator other) const
inline

Returns true if other points to the same item as this iterator; otherwise returns false.

See also
operator!=()

Definition at line 248 of file qlist.h.

248 { return i == o.i; }

◆ operator>()

template<typename T>
bool QList< T >::const_iterator::operator> ( const const_iterator other) const
inline

Returns true if the item pointed to by this iterator is greater than the item pointed to by the other iterator.

Definition at line 252 of file qlist.h.

252 { return i > other.i; }

◆ operator>=()

template<typename T>
bool QList< T >::const_iterator::operator>= ( const const_iterator other) const
inline

Returns true if the item pointed to by this iterator is greater than or equal to the item pointed to by the other iterator.

Definition at line 253 of file qlist.h.

253 { return i >= other.i; }

◆ operator[]()

template<typename T>
const T & QList< T >::const_iterator::operator[] ( int  j) const
inline

Returns the item at position *this + {j}.

This function is provided to make QList iterators behave like C++ pointers.

See also
operator+()

Definition at line 247 of file qlist.h.

247 { return i[j].t(); }
Q_INLINE_TEMPLATE T & t()
Definition: qlist.h:112

Properties

◆ i

template<typename T>
Node* QList< T >::const_iterator::i

The documentation for this class was generated from the following files: