- Qt 5.15
- Qt Core
- C++ Classes
- const_iterator
- Qt 5.15.18 Reference Documentation

# const_iterator Struct

struct QAssociativeIterable::const_iterator

The QAssociativeIterable::const_iterator allows iteration over a container in a QVariant. More...

This struct was introduced in Qt 5.2.

- List of all members, including inherited members

## Public Functions

| const_iterator(const const_iterator &other)
const_iterator & | operator=(const const_iterator &other)
| ~const_iterator()
const QVariant | key() const
const QVariant | value() const
bool | operator!=(const const_iterator &other) const
const QVariant | operator*() const
const_iterator | operator+(int j) const
const_iterator & | operator++()
const_iterator | operator++(int)
const_iterator & | operator+=(int j)
const_iterator | operator-(int j) const
const_iterator & | operator--()
const_iterator | operator--(int)
const_iterator & | operator-=(int j)
bool | operator==(const const_iterator &other) const

## Detailed Description

A QAssociativeIterable::const_iterator can only be created by a QAssociativeIterable instance, and can be used in a way similar to other stl-style iterators.

     QHash<int, QString> mapping;
     mapping.insert(7, "Seven");
     mapping.insert(11, "Eleven");
     mapping.insert(42, "Forty-two");

     QVariant variant = QVariant::fromValue(mapping);
     if (variant.canConvert<QVariantHash>()) {
         QAssociativeIterable iterable = variant.value<QAssociativeIterable>();
         // Can use foreach over the values:
         foreach (const QVariant &v, iterable) {
             qDebug() << v;
         }
         // Can use C++11 range-for over the values:
         for (const QVariant &v : iterable) {
             qDebug() << v;
         }
         // Can use iterators:
         QAssociativeIterable::const_iterator it = iterable.begin();
         const QAssociativeIterable::const_iterator end = iterable.end();
         for ( ; it != end; ++it) {
             qDebug() << *it; // The current value
             qDebug() << it.key();
             qDebug() << it.value();
         }
     }

See also QAssociativeIterable.

## Member Function Documentation

### const_iterator::const_iterator(const const_iterator &other)

Creates a copy of other.

### const_iterator &const_iterator::operator=(const const_iterator &other)

Assigns other to this.

### const_iterator::~const_iterator()

Destroys the QAssociativeIterable::const_iterator.

### const QVariant const_iterator::key() const

Returns the current key, converted to a QVariant.

### const QVariant const_iterator::value() const

Returns the current value, converted to a QVariant.

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

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

See also operator==().

### const QVariant const_iterator::operator*() const

Returns the current value, converted to a QVariant.

### const_iterator const_iterator::operator+(int j) const

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

See also operator-() and operator+=().

### const_iterator &const_iterator::operator++()

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

Calling this function on QAssociativeIterable::end() leads to undefined results.

See also operator--().

### const_iterator const_iterator::operator++(int)

This is an overloaded function.

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

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

Advances the iterator by j items.

See also operator-=() and operator+().

### const_iterator const_iterator::operator-(int j) const

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

See also operator+() and operator-=().

### 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 on QAssociativeIterable::begin() leads to undefined results.

See also operator++().

### 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 by j items.

See also operator+=() and operator-().

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

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

See also operator!=().