The QUtf8StringView class provides a unified view on UTF-8 strings with a read-only subset of the 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 |
注意： 此類的所有函數 可重入 .
| const_iterator | |
| const_pointer | |
| const_reference | |
| const_reverse_iterator | |
| difference_type | |
| iterator | |
| pointer | |
| reference | |
| reverse_iterator | |
| size_type | |
| storage_type | |
| value_type |
| QUtf8StringView () | |
| QUtf8StringView (std::nullptr_t) | |
| QUtf8StringView (const Char * str , qsizetype len ) | |
| QUtf8StringView (const Char * first , const Char * last ) | |
| QUtf8StringView (const Char (&)[N] string = N) | |
| QUtf8StringView (const Char * str ) | |
| QUtf8StringView (const Container & str ) | |
| 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 |
| int | compare (QUtf8StringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| int | compare (QStringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| int | compare (QLatin1StringView 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 |
| bool | isValidUtf8 () const |
| QUtf8StringView | last (qsizetype n ) const |
| qsizetype | length () const |
| QUtf8StringView::const_reverse_iterator | rbegin () const |
| QUtf8StringView::const_reverse_iterator | rend () const |
| qsizetype | size () const |
| QUtf8StringView | sliced (qsizetype pos ) const |
| QUtf8StringView | sliced (qsizetype pos , qsizetype n ) const |
| QString | toString () const |
| void | truncate (qsizetype n ) |
| const char8_t * | utf8 () const |
| QUtf8StringView::storage_type | operator[] (qsizetype n ) const |
| QUtf8StringView | fromArray (const Char (&)[Size] string = Size) |
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 .
QUtf8StringView accepts strings over a variety of character types:
char
(both signed and unsigned)
char8_t
(C++20 only)
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.
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
:
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 , QUtf8StringView ，和 QString .
此 typedef 提供 STL 樣式 const 迭代器為 QUtf8StringView .
另請參閱 iterator and const_reverse_iterator .
彆名化的
value_type *
。為兼容 STL (標準模闆庫) 提供。
彆名化的
value_type &
。為兼容 STL (標準模闆庫) 提供。
This typedef provides an STL-style const reverse iterator for QUtf8StringView .
另請參閱 reverse_iterator and const_iterator .
彆名化的
std::ptrdiff_t
。為兼容 STL (標準模闆庫) 提供。
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 .
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 .
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 .
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 .
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
.
彆名化的
const char
。為兼容 STL (標準模闆庫) 提供。
[since 6.5]
int
QUtf8StringView::
compare
(
QLatin1StringView
str
,
Qt::CaseSensitivity
cs
= Qt::CaseSensitive) const
[since 6.5]
int
QUtf8StringView::
compare
(
QStringView
str
,
Qt::CaseSensitivity
cs
= Qt::CaseSensitive) const
[since 6.5]
int
QUtf8StringView::
compare
(
QUtf8StringView
str
,
Qt::CaseSensitivity
cs
= Qt::CaseSensitive) const
Returns an integer that compares to zero as this string view compares to the string view str .
若 cs is Qt::CaseSensitive (the default), the comparison is case-sensitive; otherwise the comparison is case-insensitive.
This function was introduced in Qt 6.5.
[constexpr]
QUtf8StringView::
QUtf8StringView
()
構造 null 字符串視圖。
另請參閱 isNull ().
[constexpr]
QUtf8StringView::
QUtf8StringView
(
std::nullptr_t
)
構造 null 字符串視圖。
另請參閱 isNull ().
[constexpr]
template <typename Char, if_compatible_char<Char>> 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]
template <typename Char, if_compatible_char<Char>> 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, size_t N> QUtf8StringView::
QUtf8StringView
(const
Char
(&)[
N
]
string
= N)
構造字符串視圖按字符串文字
string
. The view covers the array until the first
Char(0)
is encountered, or
N
, whichever comes first. If you need the full array, use
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]
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]
template <typename Container, if_compatible_container<Container>> QUtf8StringView::
QUtf8StringView
(const
Container
&
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
容器
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).
[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 ().
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 ().
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 ().
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 code points.
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 ()，和 truncate ().
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 ().
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 ().
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]
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 ().
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 ()，和 truncate ().
[static constexpr]
template <typename Char, size_t Size, if_compatible_char<Char>>
QUtf8StringView
QUtf8StringView::
fromArray
(const
Char
(&)[
Size
]
string
= Size)
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]
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]
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 ().
[since 6.3]
bool
QUtf8StringView::
isValidUtf8
() const
返迴
true
if this string contains valid UTF-8 encoded data, or
false
否則。
This function was introduced in Qt 6.3.
[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 ()，和 truncate ().
[constexpr]
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 ().
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 ().
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]
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]
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 ()，和 truncate ().
[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 ()，和 truncate ().
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 code points.
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 ().
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 ().
[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 ().