const_iterator 类

class QJsonObject ::const_iterator

The QJsonObject::const_iterator 类提供 STL 样式 const 迭代器为 QJsonObject . 更多...

该类在 Qt 5.0 引入。

公共类型

typedef iterator_category

公共函数

const_iterator (const iterator & other )
const_iterator ()
QString key () const
QJsonValue value () const
bool operator!= (const const_iterator & other ) const
bool operator!= (const iterator & other ) const
QJsonValue 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
int operator- (const_iterator other ) const
const_iterator & operator-- ()
const_iterator operator-- ( int )
const_iterator & operator-= (int j )
QJsonValue * operator-> () const
bool operator< (const const_iterator & other ) const
bool operator<= (const const_iterator & other ) const
bool operator== (const const_iterator & other ) const
bool operator== (const iterator & other ) const
bool operator> (const const_iterator & other ) const
bool operator>= (const const_iterator & other ) const
const QJsonValue operator[] (int j )

详细描述

QJsonObject::const_iterator allows you to iterate over a QJsonObject . If you want to modify the QJsonObject as you iterate over it, you must use QJsonObject::iterator instead. It is generally good practice to use QJsonObject::const_iterator on a non-const QJsonObject as well, unless you need to change the QJsonObject through the iterator. Const iterators are slightly faster and improve code readability.

默认 QJsonObject::const_iterator constructor creates an uninitialized iterator. You must initialize it using a QJsonObject function like QJsonObject::constBegin (), QJsonObject::constEnd (),或 QJsonObject::find () before you can start iterating.

Multiple iterators can be used on the same object. Existing iterators will however become dangling if the object gets modified.

另请参阅 QJsonObject::iterator , 在 Qt 中支持 JSON ,和 JSON 保存游戏范例 .

成员类型文档编制

typedef const_iterator:: iterator_category

同义词 std::random_access_iterator_tag indicating this iterator is a random-access iterator.

注意: In Qt versions before 5.6, this was set by mistake to std::bidirectional_iterator_tag .

成员函数文档编制

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

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

返回 true if other 指向与此迭代器不同的项;否则返回 false .

另请参阅 operator== ().

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

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

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

另请参阅 operator!= ().

const_iterator:: const_iterator (const iterator & other )

构造副本为 other .

const_iterator:: const_iterator ()

Constructs an uninitialized iterator.

Functions like key (), value (), and operator++() must not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it.

另请参阅 QJsonObject::constBegin () 和 QJsonObject::constEnd ().

QString const_iterator:: key () const

Returns the current item's key.

另请参阅 value ().

QJsonValue const_iterator:: value () const

Returns the current item's value.

另请参阅 key () 和 operator* ().

QJsonValue const_iterator:: operator* () const

Returns the current item's value.

如同 value ().

另请参阅 key ().

const_iterator const_iterator:: operator+ ( int j ) const

Returns an iterator to the item at j positions forward from this iterator. If j is negative, the iterator goes backward.

This operation can be slow for large j 值。

另请参阅 operator- ().

const_iterator &const_iterator:: operator++ ()

The prefix ++ operator, ++i , advances the iterator to the next item in the object and returns an iterator to the new current item.

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

另请参阅 operator-- ().

const_iterator const_iterator:: operator++ ( int )

这是重载函数。

The postfix ++ operator, i++ , advances the iterator to the next item in the object and returns an iterator to the previously current item.

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

Advances the iterator by j items. If j is negative, the iterator goes backward.

This operation can be slow for large j 值。

另请参阅 operator-= () 和 operator+ ().

const_iterator const_iterator:: operator- ( int j ) const

Returns an iterator to the item at j positions backward from this iterator. If j is negative, the iterator goes forward.

This operation can be slow for large j 值。

另请参阅 operator+ ().

int const_iterator:: operator- ( const_iterator other ) const

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

const_iterator &const_iterator:: operator-- ()

The prefix -- operator, --i , makes the preceding item current and returns an iterator pointing to the new current item.

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

另请参阅 operator++ ().

const_iterator const_iterator:: operator-- ( int )

这是重载函数。

The postfix -- operator, i-- , makes the preceding item current and returns an iterator pointing to the previously current item.

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

Makes the iterator go back by j items. If j is negative, the iterator goes forward.

This operation can be slow for large j 值。

另请参阅 operator+= () 和 operator- ().

QJsonValue *const_iterator:: operator-> () const

Returns a pointer to the current item.

bool const_iterator:: operator< (const const_iterator & other ) const

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

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

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

bool const_iterator:: operator> (const const_iterator & other ) const

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

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

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

const QJsonValue const_iterator:: operator[] ( int j )

Returns the item at offset j from the item pointed to by this iterator (the item at position *this + j ).

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

另请参阅 operator+ ().