QUtf8StringView 類

QUtf8StringView 類提供 UTF-8 字符串統一視圖，采用隻讀子集的 QString API. 更多...

頭：	#include <QUtf8StringView>
CMake:	find_package(Qt6 REQUIRED COMPONENTS Core) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake:	QT += core
Since:	Qt 6.0

• 所有成員列錶，包括繼承成員
• 棄用成員
• QUtf8StringView is part of 用於字符串數據的類 .

此類 強烈可比較 .

此類 強烈可比較 采用 char16_t， QChar , const char16_t *, QString , QStringView ，和 QLatin1StringView .

此類 強烈可比較 with const char *, QByteArray ，和 QByteArrayView .

The contents of byte arrays is interpreted as UTF-8.

注意： 此類的所有函數 可重入 .

公共類型

	const_iterator
	const_pointer
	const_reference
	const_reverse_iterator
	difference_type
	iterator
	pointer
	reference
	reverse_iterator
	size_type
	storage_type
	value_type

公共函數

	QUtf8StringView ()
	QUtf8StringView (const Char (&)[N] string )
	QUtf8StringView (const Char * str )
	QUtf8StringView (const Container & str )
	QUtf8StringView (std::nullptr_t)
	QUtf8StringView (const Char * first , const Char * last )
	QUtf8StringView (const Char * str , qsizetype len )
QUtf8StringView::storage_type	at (qsizetype n ) const
QUtf8StringView::storage_type	back () const
QUtf8StringView::const_iterator	begin () const
QUtf8StringView::const_iterator	cbegin () const
QUtf8StringView::const_iterator	cend () const
void	chop (qsizetype n )
QUtf8StringView	chopped (qsizetype n ) const
(從 6.5 起) int	compare (QLatin1StringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const
(從 6.5 起) int	compare (QStringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const
(從 6.5 起) int	compare (QUtf8StringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const
QUtf8StringView::const_reverse_iterator	crbegin () const
QUtf8StringView::const_reverse_iterator	crend () const
QUtf8StringView::const_pointer	data () const
bool	empty () const
QUtf8StringView::const_iterator	end () const
QUtf8StringView	first (qsizetype n ) const
QUtf8StringView::storage_type	front () const
bool	isEmpty () const
bool	isNull () const
(從 6.3 起) bool	isValidUtf8 () const
QUtf8StringView	last (qsizetype n ) const
qsizetype	length () const
(從 6.8 起) qsizetype	max_size () const
QUtf8StringView::const_reverse_iterator	rbegin () const
QUtf8StringView::const_reverse_iterator	rend () const
qsizetype	size () const
(從 6.8 起) QUtf8StringView &	slice (qsizetype pos , qsizetype n )
(從 6.8 起) QUtf8StringView &	slice (qsizetype pos )
QUtf8StringView	sliced (qsizetype pos ) const
QUtf8StringView	sliced (qsizetype pos , qsizetype n ) const
QString	toString () const
void	truncate (qsizetype n )
const char8_t *	utf8 () const
(從 6.7 起) std::basic_string_view<QUtf8StringView::storage_type>	operator std::basic_string_view<QUtf8StringView::storage_type> () const
QUtf8StringView::storage_type	operator[] (qsizetype n ) const

靜態公共成員

QUtf8StringView	fromArray (const Char (&)[Size] string )
(從 6.8 起) qsizetype	maxSize ()

詳細描述

A QUtf8StringView references a contiguous portion of a UTF-8 string it does not own. It acts as an interface type to all kinds of UTF-8 string, without the need to construct a QString or QByteArray 首先。

The UTF-8 string may be represented as an array (or an array-compatible data-structure such as std::basic_string, etc.) of char8_t , char , signed char or unsigned char .

QUtf8StringView is designed as an interface type; its main use-case is as a function parameter type. When QUtf8StringViews are used as automatic variables or data members, care must be taken to ensure that the referenced string data (for example, owned by a std::u8string) outlives the QUtf8StringView on all code paths, lest the string view ends up referencing deleted data.

When used as an interface type, QUtf8StringView allows a single function to accept a wide variety of UTF-8 string data sources. One function accepting QUtf8StringView thus replaces several function overloads (taking e.g. QByteArray ), while at the same time enabling even more string data sources to be passed to the function, such as u8"Hello World" ， char8_t (C++20) or char (C++17) string literal. The char8_t incompatibility between C++17 and C++20 goes away when using QUtf8StringView.

Like all views, QUtf8StringViews should be passed by value, not by reference-to-const:

    void myfun1(QUtf8StringView sv);        // preferred
    void myfun2(const QUtf8StringView &sv); // compiles and works, but slower
					

If you want to give your users maximum freedom in what strings they can pass to your function, consider using QAnyStringView 代替。

QUtf8StringView can also be used as the return value of a function. If you call a function returning QUtf8StringView, take extra care to not keep the QUtf8StringView around longer than the function promises to keep the referenced string data alive. If in doubt, obtain a strong reference to the data by calling toString () to convert the QUtf8StringView into a QString .

QUtf8StringView is a 文字類型 .

兼容字符類型

QUtf8StringView accepts strings over a variety of character types:

• char (有符號和無符號兩者)
• char8_t (僅 C++20)

大小和子字符串

All sizes and positions in QUtf8StringView functions are in UTF-8 code points (that is, UTF-8 multibyte sequences count as two, three or four, depending on their length). QUtf8StringView does not an attempt to detect or prevent slicing right through UTF-8 multibyte sequences. This is similar to the situation with QStringView and surrogate pairs.

C++20、char8_t 和 QUtf8StringView

In C++20, u8"" string literals changed their type from const char[] to const char8_t[] . If Qt 6 could have depended on C++20, QUtf8StringView would store char8_t natively, and the following functions and aliases would use (pointers to) char8_t :

• storage_type , value_type , etc
• begin (), end (), data (), etc
• front (), back (), at (), operator[]()

This is what QUtf8StringView is expected to look like in Qt 7, but for Qt 6, this was not possible. Instead of locking users into a C++17-era interface for the next decade, Qt provides two QUtf8StringView classes, in different (inline) namespaces. The first, in namespace q_no_char8_t , has a value_type of const char and is universally available. The second, in namespace q_has_char8_t , has a value_type of const char8_t and is only available when compiling in C++20 mode.

q_no_char8_t is an inline namespace regardless of C++ edition, to avoid accidental binary incompatibilities. To use the char8_t version, you need to name it explicitly with q_has_char8_t::QUtf8StringView .

Internally, both are instantiations of the same template class, QBasicUtf8StringView. Please do not use the template class's name in your source code.

另請參閱 QAnyStringView , QStringView , QLatin1StringView ，和 QString .

成員類型文檔編製

QUtf8StringView:: const_iterator

此 typedef 提供 STL 樣式 const 迭代器為 QUtf8StringView .

另請參閱 iterator and const_reverse_iterator .

QUtf8StringView:: const_pointer

彆名化的 value_type * 。為兼容 STL (標準模闆庫) 提供。

QUtf8StringView:: const_reference

彆名化的 value_type & 。為兼容 STL (標準模闆庫) 提供。

QUtf8StringView:: const_reverse_iterator

This typedef provides an STL-style const reverse iterator for QUtf8StringView .

另請參閱 reverse_iterator and const_iterator .

QUtf8StringView:: difference_type

彆名化的 std::ptrdiff_t 。為兼容 STL (標準模闆庫) 提供。

QUtf8StringView:: iterator

此 typedef 提供 STL 樣式 const 迭代器為 QUtf8StringView .

QUtf8StringView does not support mutable iterators, so this is the same as const_iterator .

另請參閱 const_iterator and reverse_iterator .

QUtf8StringView:: pointer

彆名化的 value_type * 。為兼容 STL (標準模闆庫) 提供。

QUtf8StringView does not support mutable pointers, so this is the same as const_pointer .

QUtf8StringView:: reference

彆名化的 value_type & 。為兼容 STL (標準模闆庫) 提供。

QUtf8StringView does not support mutable references, so this is the same as const_reference .

QUtf8StringView:: reverse_iterator

This typedef provides an STL-style const reverse iterator for QUtf8StringView .

QUtf8StringView does not support mutable reverse iterators, so this is the same as const_reverse_iterator .

另請參閱 const_reverse_iterator and iterator .

QUtf8StringView:: size_type

彆名化的 qsizetype。為兼容 STL (標準模闆庫) 提供。

[alias] QUtf8StringView:: storage_type

彆名化的 char .

QUtf8StringView:: value_type

彆名化的 const char 。為兼容 STL (標準模闆庫) 提供。

成員函數文檔編製

[noexcept, since 6.5] int QUtf8StringView:: compare ( QLatin1StringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const

[noexcept, since 6.5] int QUtf8StringView:: compare ( QStringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const

[noexcept, since 6.5] int QUtf8StringView:: compare ( QUtf8StringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Compares this string view with str and returns a negative integer if this string view is less than str ，正整數若大於 str ，和 0 若它們相等。

若 cs is Qt::CaseSensitive (默認)，比較區分大小寫；否則，比較不區分大小寫。

該函數在 Qt 6.5 引入。

[constexpr noexcept] QUtf8StringView:: QUtf8StringView ()

構造 null 字符串視圖。

另請參閱 isNull ().

[constexpr noexcept] template <typename Char, size_t N> QUtf8StringView:: QUtf8StringView (const Char (&)[ N ] string )

構造字符串視圖按字符串文字 string 。視圖覆蓋數組，直到第 1 個 Char(0) 被遇到，或 N ，以先到的為準。若需要完整數組，使用 fromArray () 代替。

string 必須在此字符串視圖對象的壽命內保持有效。

This constructor only participates in overload resolution if string is an actual array and if Char is a compatible character type. The compatible character types are: char8_t , char , signed char and unsigned char .

另請參閱 fromArray ().

[constexpr noexcept] template <typename Char> QUtf8StringView:: QUtf8StringView (const Char * str )

構造字符串視圖對 str . The length is determined by scanning for the first Char(0) .

str 必須在此字符串視圖對象的壽命內保持有效。

傳遞 nullptr as str 是安全的且結果在 null 字符串視圖中。

This constructor only participates in overload resolution if str is not an array and if Char is a compatible character type. The compatible character types are: char8_t , char , signed char and unsigned char .

[constexpr noexcept] template <typename Container, QUtf8StringView::if_compatible_container<Container> = true> QUtf8StringView:: QUtf8StringView (const 容器 & str )

構造字符串視圖對 str 。長度取自 std::size(str) .

std::data(str) 必須在此字符串視圖對象的壽命內保持有效。

This constructor only participates in overload resolution if Container is a container with a compatible character type as value_type . The compatible character types are: char8_t , char , signed char and unsigned char .

The string view will be empty if and only if std::size(str) == 0 . It is unspecified whether this constructor can result in a null string view ( std::data(str) would have to return nullptr for this).

另請參閱 isNull () 和 isEmpty ().

[constexpr noexcept] QUtf8StringView:: QUtf8StringView ( std::nullptr_t )

構造 null 字符串視圖。

另請參閱 isNull ().

[constexpr] template <typename Char, QUtf8StringView::if_compatible_char<Char> = true> QUtf8StringView:: QUtf8StringView (const Char * first , const Char * last )

構造字符串視圖對 first 按長度 ( last - first ).

範圍 [first,last) 必須在此字符串視圖對象的壽命內保持有效。

傳遞 \nullptr as first 是安全的若 last is nullptr , too, and results in a null string view.

行為未定義若 last precedes first ，或 first is nullptr and last is not.

This constructor only participates in overload resolution if Char is a compatible character type. The compatible character types are: char8_t , char , signed char and unsigned char .

[constexpr] template <typename Char, QUtf8StringView::if_compatible_char<Char> = true> QUtf8StringView:: QUtf8StringView (const Char * str , qsizetype len )

構造字符串視圖對 str 按長度 len .

範圍 [str,len) 必須在此字符串視圖對象的壽命內保持有效。

傳遞 nullptr as str 是安全的若 len is 0, too, and results in a null string view.

行為未定義若 len is negative or, when positive, if str is nullptr .

This constructor only participates in overload resolution if Char is a compatible character type. The compatible character types are: char8_t , char , signed char and unsigned char .

[constexpr] QUtf8StringView::storage_type QUtf8StringView:: at ( qsizetype n ) const

Returns the code point at position n 在此字符串視圖。

行為未定義若 n is negative or not less than size ().

另請參閱 operator[] (), front ()，和 back ().

[constexpr] QUtf8StringView::storage_type QUtf8StringView:: back () const

Returns the last code point in the string view. Same as last ().

此函數為兼容 STL (標準模闆庫) 提供。

警告： 在空字符串視圖調用此函數，將構成未定義行為。

另請參閱 front ().

[noexcept] QUtf8StringView::const_iterator QUtf8StringView:: begin () const

返迴常量 STL 樣式迭代器 pointing to the first code point in the string view.

此函數為兼容 STL (標準模闆庫) 提供。

另請參閱 end (), cbegin (), rbegin ()，和 data ().

[noexcept] QUtf8StringView::const_iterator QUtf8StringView:: cbegin () const

如同 begin ().

此函數為兼容 STL (標準模闆庫) 提供。

另請參閱 cend (), begin (), crbegin ()，和 data ().

[noexcept] QUtf8StringView::const_iterator QUtf8StringView:: cend () const

如同 end ().

此函數為兼容 STL (標準模闆庫) 提供。

另請參閱 cbegin (), end ()，和 crend ().

[constexpr] void QUtf8StringView:: chop ( qsizetype n )

截取此字符串視圖按 n 代碼點。

如同 *this = first(size() - n) .

注意： 行為未定義當 n < 0 or n > size ().

另請參閱 sliced (), first (), last (), chopped ()，和 truncate ().

[constexpr] QUtf8StringView QUtf8StringView:: chopped ( qsizetype n ) const

返迴子字符串長度 size () - n 起始於此對象的開頭。

如同 first(size() - n) .

注意： 行為未定義當 n < 0 or n > size ().

另請參閱 sliced (), first (), last (), chop (), truncate ()，和 slice ().

[noexcept] QUtf8StringView::const_reverse_iterator QUtf8StringView:: crbegin () const

如同 rbegin ().

此函數為兼容 STL (標準模闆庫) 提供。

另請參閱 crend (), rbegin ()，和 cbegin ().

[noexcept] QUtf8StringView::const_reverse_iterator QUtf8StringView:: crend () const

如同 rend ().

此函數為兼容 STL (標準模闆庫) 提供。

另請參閱 crbegin (), rend ()，和 cend ().

[constexpr noexcept] QUtf8StringView::const_pointer QUtf8StringView:: data () const

Returns a const pointer to the first code point in the string view.

注意： The character array represented by the return value is not null-terminated.

另請參閱 begin (), end ()，和 utf8 ().

[constexpr noexcept] bool QUtf8StringView:: empty () const

Returns whether this string view is empty - that is, whether size() == 0 .

此函數為兼容 STL (標準模闆庫) 提供。

另請參閱 isEmpty (), isNull (), size ()，和 length ().

[noexcept] QUtf8StringView::const_iterator QUtf8StringView:: end () const

返迴常量 STL 樣式迭代器 pointing to the imaginary code point after the last code point in the list.

此函數為兼容 STL (標準模闆庫) 提供。

另請參閱 begin (), cend ()，和 rend ().

[constexpr] QUtf8StringView QUtf8StringView:: first ( qsizetype n ) const

Returns a string view that contains the first n code points of this string view.

注意： 行為未定義當 n < 0 or n > size ().

另請參閱 last (), sliced (), chopped (), chop (), truncate ()，和 slice ().

[static constexpr noexcept] template <typename Char, size_t Size, QUtf8StringView::if_compatible_char<Char> = true> QUtf8StringView QUtf8StringView:: fromArray (const Char (&)[ Size ] string )

Constructs a string view on the full character string literal string , including any trailing Char(0) . If you don't want the null-terminator included in the view then you can chop () it off when you are certain it is at the end. Alternatively you can use the constructor overload taking an array literal which will create a view up to, but not including, the first null-terminator in the data.

string 必須在此字符串視圖對象的壽命內保持有效。

This function will work with any array literal if Char is a compatible character type. The compatible character types are: char8_t , char , signed char and unsigned char .

[constexpr] QUtf8StringView::storage_type QUtf8StringView:: front () const

Returns the first code point in the string view. Same as first ().

此函數為兼容 STL (標準模闆庫) 提供。

警告： 在空字符串視圖調用此函數，將構成未定義行為。

另請參閱 back ().

[constexpr noexcept] bool QUtf8StringView:: isEmpty () const

Returns whether this string view is empty - that is, whether size() == 0 .

This function is provided for compatibility with other Qt containers.

另請參閱 empty (), isNull (), size ()，和 length ().

[constexpr noexcept] bool QUtf8StringView:: isNull () const

Returns whether this string view is null - that is, whether data() == nullptr .

This functions is provided for compatibility with other Qt containers.

另請參閱 empty (), isEmpty (), size ()，和 length ().

[noexcept, since 6.3] bool QUtf8StringView:: isValidUtf8 () const

返迴 true if this string contains valid UTF-8 encoded data, or false 否則。

該函數在 Qt 6.3 引入。

[constexpr] QUtf8StringView QUtf8StringView:: last ( qsizetype n ) const

Returns a string view that contains the last n code points of this string view.

注意： 行為未定義當 n < 0 or n > size ().

另請參閱 first (), sliced (), chopped (), chop (), truncate ()，和 slice ().

[constexpr noexcept] qsizetype QUtf8StringView:: length () const

如同 size ().

This function is provided for compatibility with other Qt containers.

另請參閱 empty (), isEmpty (), isNull ()，和 size ().

[static constexpr noexcept, since 6.8] qsizetype QUtf8StringView:: maxSize ()

It returns the maximum number of elements that the view can theoretically represent. In practice, the number can be much smaller, limited by the amount of memory available to the system.

該函數在 Qt 6.8 引入。

[constexpr noexcept, since 6.8] qsizetype QUtf8StringView:: max_size () const

此函數為兼容 STL (標準模闆庫) 提供。

返迴 maxSize ().

該函數在 Qt 6.8 引入。

[noexcept] QUtf8StringView::const_reverse_iterator QUtf8StringView:: rbegin () const

返迴常量 STL-style reverse iterator pointing to the first code point in the string view, in reverse order.

此函數為兼容 STL (標準模闆庫) 提供。

另請參閱 rend (), crbegin ()，和 begin ().

[noexcept] QUtf8StringView::const_reverse_iterator QUtf8StringView:: rend () const

返迴 STL-style reverse iterator pointing to one past the last code point in the string view, in reverse order.

此函數為兼容 STL (標準模闆庫) 提供。

另請參閱 rbegin (), crend ()，和 end ().

[constexpr noexcept] qsizetype QUtf8StringView:: size () const

Returns the size of this string view, in UTF-8 code points (that is, multi-byte sequences count as more than one for the purposes of this function, the same as surrogate pairs in QString and QStringView ).

另請參閱 empty (), isEmpty (), isNull ()，和 length ().

[constexpr, since 6.8] QUtf8StringView &QUtf8StringView:: slice ( qsizetype pos , qsizetype n )

Modifies this string view to start at position pos , extending for n 代碼點。

注意： 行為未定義當 pos < 0, n < 0, or pos + n > size ().

該函數在 Qt 6.8 引入。

另請參閱 sliced (), first (), last (), chopped (), chop ()，和 truncate ().

[constexpr, since 6.8] QUtf8StringView &QUtf8StringView:: slice ( qsizetype pos )

這是重載函數。

Modifies this string view to start at position pos , extending to its end.

注意： 行為未定義當 pos < 0 or pos > size ().

該函數在 Qt 6.8 引入。

另請參閱 sliced (), first (), last (), chopped (), chop ()，和 truncate ().

[constexpr] QUtf8StringView QUtf8StringView:: sliced ( qsizetype pos ) const

Returns a string view starting at position pos in this object, and extending to its end.

注意： 行為未定義當 pos < 0 or pos > size ().

另請參閱 first (), last (), chopped (), chop (), truncate ()，和 slice ().

[constexpr] QUtf8StringView QUtf8StringView:: sliced ( qsizetype pos , qsizetype n ) const

Returns a string view containing n code points of this string view, starting at position pos .

注意： 行為未定義當 pos < 0, n < 0, or pos + n > size ().

另請參閱 first (), last (), chopped (), chop (), truncate ()，和 slice ().

QString QUtf8StringView:: toString () const

Returns a deep copy of this string view's data as a QString .

The return value will be a null QString if and only if this string view is null.

[constexpr] void QUtf8StringView:: truncate ( qsizetype n )

Truncates this string view to n 代碼點。

如同 *this = first(n) .

注意： 行為未定義當 n < 0 or n > size ().

另請參閱 sliced (), first (), last (), chopped ()，和 chop ().

[noexcept] const char8_t *QUtf8StringView:: utf8 () const

Returns a const pointer to the first code point in the string view.

The result is returned as a const char8_t* , so this function is only available when compiling in C++20 mode.

注意： The character array represented by the return value is not null-terminated.

另請參閱 begin (), end ()，和 data ().

[noexcept, since 6.7] std::basic_string_view < QUtf8StringView::storage_type > QUtf8StringView:: operator std::basic_string_view<QUtf8StringView::storage_type> () const

轉換此 QUtf8StringView object to a std::basic_string_view object. The returned view will have the same data pointer and length of this view. The character type of the returned view will be storage_type .

該函數在 Qt 6.7 引入。

[constexpr] QUtf8StringView::storage_type QUtf8StringView:: operator[] ( qsizetype n ) const

Returns the code point at position n 在此字符串視圖。

行為未定義若 n is negative or not less than size ().

另請參閱 at (), front ()，和 back ().

內容

1. 公共類型

2. 公共函數

3. 靜態公共成員

4. 詳細描述

5. 兼容字符類型

6. 大小和子字符串

7. C++20、char8_t 和 QUtf8StringView