Contents

• Public Types
• Public Functions
• Detailed Description

Detailed Description

TheQSet::const_iterator class provides an STL-style const iterator forQSet.

QSet features bothSTL-style iterators andJava-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.

QSet<Key, T>::const_iterator allows you to iterate over aQSet. If you want to modify theQSet as you iterate over it, you must useQSet::iterator instead. It is generally good practice to useQSet::const_iterator on a non-constQSet as well, unless you need to change theQSet through the iterator. Const iterators are slightly faster, and can improve code readability.

The defaultQSet::const_iterator constructor creates an uninitialized iterator. You must initialize it using a function likeQSet::begin(),QSet::end(), orQSet::insert() before you can start iterating. Here's a typical loop that prints all the items stored in a set:

QSet<QString> set;set<<"January"<<"February"<<...<<"December";QSet<QString>::const_iterator i;for (i= set.begin(); i!= set.end();++i)qDebug()<<*i;

STL-style iterators can be used as arguments togeneric algorithms. For example, here's how to find an item in the set using theqFind() algorithm:

QSet<QString> set;...QSet<QString>::iterator it=qFind(set.begin(), set.end(),"Jeanette");if (it!= set.constEnd())    cout<<"Found Jeanette"<< endl;

Multiple iterators can be used on the same set. However, you may not attempt to modify the container while iterating on it.

Member Type Documentation

typedef const_iterator::iterator_category

Synonyms forstd::bidirectional_iterator_tag indicating these iterators are bidirectional iterators.

Member Function Documentation

const_iterator::const_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 alsoQSet::begin() andQSet::end().

const_iterator::const_iterator(constconst_iterator & other)

Constructs a copy ofother.

const_iterator::const_iterator(constiterator & other)

This is an overloaded function.

Constructs a copy ofother.

This function was introduced in Qt 4.2.

bool const_iterator::operator!=(constconst_iterator & other) const

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

See alsooperator==().

constT & const_iterator::operator*() const

Returns a reference to the current item.

See alsooperator->().

const_iterator const_iterator::operator+(int j) const

Returns an iterator to the item atj positions forward from this iterator. (Ifj is negative, the iterator goes backward.)

This operation can be slow for largej values.

See alsooperator-().

const_iterator & const_iterator::operator++()

The prefix ++ operator (++it) advances the iterator to the next item in the set and returns an iterator to the new current item.

Calling this function onQSet::constEnd() leads to undefined results.

See alsooperator--().

const_iterator const_iterator::operator++(int)

This is an overloaded function.

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

const_iterator & const_iterator::operator+=(int j)

Advances the iterator byj items. (Ifj is negative, the iterator goes backward.)

This operation can be slow for largej values.

See alsooperator-=() andoperator+().

const_iterator const_iterator::operator-(int j) const

Returns an iterator to the item atj positions backward from this iterator. (Ifj is negative, the iterator goes forward.)

This operation can be slow for largej values.

See alsooperator+().

const_iterator & const_iterator::operator--()

The prefix -- operator (--it) makes the preceding item current and returns an iterator to the new current item.

Calling this function onQSet::begin() leads to undefined results.

See alsooperator++().

const_iterator const_iterator::operator--(int)

This is an overloaded function.

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

const_iterator & const_iterator::operator-=(int j)

Makes the iterator go back byj items. (Ifj is negative, the iterator goes forward.)

This operation can be slow for largej values.

See alsooperator+=() andoperator-().

constT * const_iterator::operator->() const

Returns a pointer to the current item.

See alsooperator*().

const_iterator & const_iterator::operator=(constconst_iterator & other)

Assignsother to this iterator.

bool const_iterator::operator==(constconst_iterator & other) const

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

See alsooperator!=().