The QStringView class provides a unified view on UTF-16 strings with a read-only subset of the QString API. 更多...
| 头： | #include <QStringView> |
| qmake: | QT += core |
| Since: | Qt 5.10 |
注意： 此类的所有函数 可重入 .
| typedef | const_iterator |
| typedef | const_pointer |
| typedef | const_reference |
| typedef | const_reverse_iterator |
| typedef | difference_type |
| typedef | iterator |
| typedef | pointer |
| typedef | reference |
| typedef | reverse_iterator |
| typedef | size_type |
| typedef | storage_type |
| typedef | value_type |
| QStringView () | |
| QStringView ( std::nullptr_t ) | |
| QStringView (const Char * str , qsizetype len ) | |
| QStringView (const Char * first , const Char * last ) | |
| QStringView (const Char (&)[N] string = ...) | |
| QStringView (const Char * str ) | |
| QStringView (const QString & str ) | |
| QStringView (const QStringRef & str ) | |
| QStringView (const StdBasicString & str ) | |
| QChar | at (qsizetype n ) const |
| QChar | back () const |
| QStringView::const_iterator | begin () const |
| QStringView::const_iterator | cbegin () const |
| QStringView::const_iterator | cend () const |
| void | chop (qsizetype length ) |
| QStringView | chopped (qsizetype length ) const |
| int | compare (QStringView other , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| QStringView::const_reverse_iterator | crbegin () const |
| QStringView::const_reverse_iterator | crend () const |
| QStringView::const_pointer | data () const |
| bool | empty () const |
| QStringView::const_iterator | end () const |
| bool | endsWith (QStringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| bool | endsWith (QLatin1String l1 , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| bool | endsWith (QChar ch ) const |
| bool | endsWith (QChar ch , Qt::CaseSensitivity cs ) const |
| QChar | first () const |
| QChar | front () const |
| bool | isEmpty () const |
| bool | isNull () const |
| bool | isRightToLeft () const |
| QChar | last () const |
| QStringView | left (qsizetype length ) const |
| int | length () const |
| QStringView | mid (qsizetype start ) const |
| QStringView | mid (qsizetype start , qsizetype length ) const |
| QStringView::const_reverse_iterator | rbegin () const |
| QStringView::const_reverse_iterator | rend () const |
| QStringView | right (qsizetype length ) const |
| qsizetype | size () const |
| bool | startsWith (QStringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| bool | startsWith (QLatin1String l1 , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| bool | startsWith (QChar ch ) const |
| bool | startsWith (QChar ch , Qt::CaseSensitivity cs ) const |
| QByteArray | toLatin1 () const |
| QByteArray | toLocal8Bit () const |
| QString | toString () const |
| QVector<uint> | toUcs4 () const |
| QByteArray | toUtf8 () const |
| QStringView | trimmed () const |
| void | truncate (qsizetype length ) |
| const QStringView::storage_type * | utf16 () const |
| QChar | operator[] (qsizetype n ) const |
| uint | qHash (QStringView key , uint seed = ...) |
The QStringView class provides a unified view on UTF-16 strings with a read-only subset of the QString API.
A QStringView references a contiguous portion of a UTF-16 string it does not own. It acts as an interface type to all kinds of UTF-16 string, without the need to construct a QString 首先。
The UTF-16 string may be represented as an array (or an array-compatible data-structure such as
QString
, std::basic_string, etc.) of
QChar
,
ushort
,
char16_t
(on compilers that support C++11 Unicode strings) or (on platforms, such as Windows, where it is a 16-bit type)
wchar_t
.
QStringView is designed as an interface type; its main use-case is as a function parameter type. When QStringViews are used as automatic variables or data members, care must be taken to ensure that the referenced string data (for example, owned by a QString ) outlives the QStringView on all code paths, lest the string view ends up referencing deleted data.
When used as an interface type,
QStringView
allows a single function to accept a wide variety of UTF-16 string data sources. One function accepting
QStringView
thus replaces three function overloads (taking
QString
,
QStringRef
，和
(const QChar*, int)
), while at the same time enabling even more string data sources to be passed to the function, such as
u"Hello World"
，
char16_t
字符串文字。
QStringViews should be passed by value, not by reference-to-const:
void myfun1(QStringView sv); // preferred
void myfun2(const QStringView &sv); // compiles and works, but slower
If you want to give your users maximum freedom in what strings they can pass to your function, accompany the QStringView overload with overloads for
void fun(QChar ch) { fun(QStringView(&ch, 1)); }
even though, for technical reasons, QStringView cannot provide a QChar constructor by itself.
QStringView can also be used as the return value of a function. If you call a function returning QStringView , take extra care to not keep the QStringView 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 QStringView 成 QString .
QStringView
是
文字类型
, but since it stores data as
char16_t
, iteration is not
constexpr
(casts from
const char16_t*
to
const QChar*
, which is not allowed in
constexpr
functions). You can use an indexed loop and/or
utf16
() 在
constexpr
contexts instead.
注意： We strongly discourage the use of QList < QStringView >, because QList is a very inefficient container for QStringViews (it would heap-allocate every element). Use QVector (or std::vector) to hold QStringViews instead.
另请参阅 QString and QStringRef .
此 typedef 提供 STL 样式 const 迭代器为 QStringView .
另请参阅 iterator and const_reverse_iterator .
别名化的
value_type *
。为兼容 STL (标准模板库) 提供。
别名化的
value_type &
。为兼容 STL (标准模板库) 提供。
This typedef provides an STL-style const reverse iterator for QStringView .
另请参阅 reverse_iterator and const_iterator .
别名化的
std::ptrdiff_t
。为兼容 STL (标准模板库) 提供。
此 typedef 提供 STL 样式 const 迭代器为 QStringView .
QStringView does not support mutable iterators, so this is the same as const_iterator .
另请参阅 const_iterator and reverse_iterator .
别名化的
value_type *
。为兼容 STL (标准模板库) 提供。
QStringView does not support mutable pointers, so this is the same as const_pointer .
别名化的
value_type &
。为兼容 STL (标准模板库) 提供。
QStringView does not support mutable references, so this is the same as const_reference .
This typedef provides an STL-style const reverse iterator for QStringView .
QStringView does not support mutable reverse iterators, so this is the same as const_reverse_iterator .
另请参阅 const_reverse_iterator and iterator .
别名化的 qsizetype。为兼容 STL (标准模板库) 提供。
Unlike other Qt classes,
QStringView
uses qsizetype as its
size_type
, to allow accepting data from
std::basic_string
without truncation. The Qt API functions, for example
length
(), return
int
, while the STL-compatible functions, for example
size
(), return
size_type
.
别名化的
char16_t
for non-Windows or if Q_COMPILER_UNICODE_STRINGS is defined. Otherwise, alias for
wchar_t
.
别名化的
const QChar
。为兼容 STL (标准模板库) 提供。
返回
true
if this string-view ends with string-view
str
, Latin-1 string
l1
, or character
ch
, respectively; otherwise returns
false
.
若 cs is Qt::CaseSensitive (默认)，搜索区分大小写；否则，搜索不区分大小写。
另请参阅 startsWith ().
返回
true
if this string-view starts with string-view
str
, Latin-1 string
l1
, or character
ch
, respectively; otherwise returns
false
.
若 cs is Qt::CaseSensitive (默认)，搜索区分大小写；否则，搜索不区分大小写。
另请参阅 endsWith ().
构造 null 字符串视图。
另请参阅 isNull ().
构造 null 字符串视图。
另请参阅 isNull ().
构造字符串视图对 str 按长度 len .
范围
[str,len)
must remain valid for the lifetime of this string view object.
传递
nullptr
as
str
是安全的若
len
is 0, too, and results in a null string view.
行为未定义若
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:
QChar
,
ushort
,
char16_t
and (on platforms, such as Windows, where it is a 16-bit type)
wchar_t
.
构造字符串视图对 first 按长度 ( last - first ).
范围
[first,last)
must remain valid for the lifetime of this string view object.
传递
nullptr
as
first
是安全的若
last
is nullptr, too, and results in a null string view.
行为未定义若
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:
QChar
,
ushort
,
char16_t
and (on platforms, such as Windows, where it is a 16-bit type)
wchar_t
.
Constructs a string view on the character string literal
string
. The length is set to
N-1
, excluding the trailing {Char(0)}. If you need the full array, use the constructor from pointer and size instead:
auto sv = QStringView(array, std::size(array)); // using C++17 std::size()
string must remain valid for the lifetime of this string view object.
This constructor only participates in overload resolution if
string
is an actual array and
Char
is a compatible character type. The compatible character types are:
QChar
,
ushort
,
char16_t
and (on platforms, such as Windows, where it is a 16-bit type)
wchar_t
.
构造字符串视图对
str
. The length is determined by scanning for the first
Char(0)
.
str must remain valid for the lifetime of this string view object.
传递
nullptr
as
str
是安全的且结果在 null 字符串视图中。
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:
QChar
,
ushort
,
char16_t
and (on platforms, such as Windows, where it is a 16-bit type)
wchar_t
.
构造字符串视图对 str .
str.data()
must remain valid for the lifetime of this string view object.
字符串视图将为 null 当且仅当
str.isNull()
.
构造字符串视图对 str .
str.data()
must remain valid for the lifetime of this string view object.
字符串视图将为 null 当且仅当
str.isNull()
.
构造字符串视图对
str
。长度取自
str.size()
.
str.data()
must remain valid for the lifetime of this string view object.
This constructor only participates in overload resolution if
StdBasicString
is an instantiation of
std::basic_string
with a compatible character type. The compatible character types are:
QChar
,
ushort
,
char16_t
and (on platforms, such as Windows, where it is a 16-bit type)
wchar_t
.
The string view will be empty if and only if
str.empty()
. It is unspecified whether this constructor can result in a null string view (
str.data()
would have to return
nullptr
for this).
返回字符位于位置 n 在此字符串视图。
行为未定义若 n is negative or not less than size ().
另请参阅 operator[] (), front ()，和 back ().
返回字符串中的最后一个字符。如同 last ().
此函数为兼容 STL (标准模板库) 提供。
警告： 在空字符串视图调用此函数，将构成未定义行为。
另请参阅 front (), first ()，和 last ().
返回常量 STL 样式迭代器 指向字符串中的首个字符。
此函数为兼容 STL (标准模板库) 提供。
另请参阅 end (), cbegin (), rbegin ()，和 data ().
如同 begin ().
此函数为兼容 STL (标准模板库) 提供。
另请参阅 cend (), begin (), crbegin ()，和 data ().
如同 end ().
此函数为兼容 STL (标准模板库) 提供。
另请参阅 cbegin (), end ()，和 crend ().
截取此字符串视图按 length 字符。
如同
*this = left(size() - length)
.
注意： 行为未定义当 length < 0 or length > size ().
另请参阅 mid (), left (), right (), chopped ()，和 truncate ().
返回子字符串长度 size () - length 起始于此对象的开头。
如同
left(size() - length)
.
注意： 行为未定义当 length < 0 or length > size ().
另请参阅 mid (), left (), right (), chop ()，和 truncate ().
Compares this string-view with the other string-view and returns an integer less than, equal to, or greater than zero if this string-view is less than, equal to, or greater than the other string-view.
若 cs is Qt::CaseSensitive , the comparison is case sensitive; otherwise the comparison is case insensitive.
该函数在 Qt 5.12 引入。
另请参阅 operator== (), operator< ()，和 operator> ().
如同 rbegin ().
此函数为兼容 STL (标准模板库) 提供。
另请参阅 crend (), rbegin ()，和 cbegin ().
如同 rend ().
此函数为兼容 STL (标准模板库) 提供。
另请参阅 crbegin (), rend ()，和 cend ().
Returns a const pointer to the first character in the string.
注意： The character array represented by the return value is not null-terminated.
另请参阅 begin (), end ()，和 utf16 ().
Returns whether this string view is empty - that is, whether
size() == 0
.
此函数为兼容 STL (标准模板库) 提供。
另请参阅 isEmpty (), isNull (), size ()，和 length ().
返回常量 STL 样式迭代器 pointing to the imaginary character after the last character in the list.
此函数为兼容 STL (标准模板库) 提供。
另请参阅 begin (), cend ()，和 rend ().
Returns the first character in the string. Same as front ().
This function is provided for compatibility with other Qt containers.
警告： 在空字符串视图调用此函数，将构成未定义行为。
另请参阅 front (), back ()，和 last ().
Returns the first character in the string. Same as first ().
此函数为兼容 STL (标准模板库) 提供。
警告： 在空字符串视图调用此函数，将构成未定义行为。
另请参阅 back (), first ()，和 last ().
Returns whether this string view is empty - that is, whether
size() == 0
.
This function is provided for compatibility with other Qt containers.
另请参阅 empty (), isNull (), size ()，和 length ().
Returns whether this string view is null - that is, whether
data() == nullptr
.
This functions is provided for compatibility with other Qt containers.
另请参阅 empty (), isEmpty (), size ()，和 length ().
返回
true
if the string is read right to left.
该函数在 Qt 5.11 引入。
另请参阅 QString::isRightToLeft ().
返回字符串中的最后一个字符。如同 back ().
This function is provided for compatibility with other Qt containers.
警告： 在空字符串视图调用此函数，将构成未定义行为。
另请参阅 back (), front ()，和 first ().
返回子字符串长度 length starting at position 0 in this object.
注意： 行为未定义当 length < 0 or length > size ().
另请参阅 mid (), right (), chopped (), chop ()，和 truncate ().
如同
size
(), except returns the result as an
int
.
This function is provided for compatibility with other Qt containers.
警告：
QStringView
can represent strings with more than 2
31
characters. Calling this function on a string view for which
size
() returns a value greater than
INT_MAX
constitutes undefined behavior.
另请参阅 empty (), isEmpty (), isNull ()，和 size ().
Returns the substring starting at position start in this object, and extending to the end of the string.
注意： 行为未定义当 start < 0 or start > size ().
另请参阅 left (), right (), chopped (), chop ()，和 truncate ().
这是重载函数。
返回子字符串长度 length 起始于位置 start 在此对象。
注意： 行为未定义当 start < 0, length < 0, or start + length > size ().
另请参阅 left (), right (), chopped (), chop ()，和 truncate ().
返回常量 STL-style reverse iterator pointing to the first character in the string, in reverse order.
此函数为兼容 STL (标准模板库) 提供。
另请参阅 rend (), crbegin ()，和 begin ().
返回 STL-style reverse iterator pointing to one past the last character in the string, in reverse order.
此函数为兼容 STL (标准模板库) 提供。
另请参阅 rbegin (), crend ()，和 end ().
返回子字符串长度 length 起始于位置 size () - length 在此对象。
注意： 行为未定义当 length < 0 or length > size ().
另请参阅 mid (), left (), chopped (), chop ()，和 truncate ().
Returns the size of this string view, in UTF-16 code points (that is, surrogate pairs count as two for the purposes of this function, the same as in QString and QStringRef ).
另请参阅 empty (), isEmpty (), isNull ()，和 length ().
Returns a Latin-1 representation of the string as a QByteArray .
The behavior is undefined if the string contains non-Latin1 characters.
另请参阅 toUtf8 (), toLocal8Bit ()，和 QTextCodec .
Returns a local 8-bit representation of the string as a QByteArray .
QTextCodec::codecForLocale () is used to perform the conversion from Unicode. If the locale's encoding could not be determined, this function does the same as toLatin1 ().
The behavior is undefined if the string contains characters not supported by the locale's 8-bit encoding.
另请参阅 toLatin1 (), toUtf8 ()，和 QTextCodec .
Returns a deep copy of this string view's data as a QString .
The return value will be the null QString if and only if this string view is null.
警告：
QStringView
can store strings with more than 2
30
characters while
QString
cannot. Calling this function on a string view for which
size
() returns a value greater than
INT_MAX / 2
constitutes undefined behavior.
Returns a UCS-4/UTF-32 representation of the string as a QVector <uint>.
UCS-4 is a Unicode codec and therefore it is lossless. All characters from this string will be encoded in UCS-4. Any invalid sequence of code units in this string is replaced by the Unicode replacement character (
QChar::ReplacementCharacter
, which corresponds to
U+FFFD
).
The returned vector is not 0-terminated.
另请参阅 toUtf8 (), toLatin1 (), toLocal8Bit ()，和 QTextCodec .
Returns a UTF-8 representation of the string as a QByteArray .
UTF-8 is a Unicode codec and can represent all characters in a Unicode string like QString .
另请参阅 toLatin1 (), toLocal8Bit ()，和 QTextCodec .
Strips leading and trailing whitespace and returns the result.
空白意味着任何字符其。
QChar::isSpace
() 返回
true
。这包括 ASCII 字符 \t、\n、\v、\f、\r、及 " "。
Truncates this string view to length length .
如同
*this = left(length)
.
注意： 行为未定义当 length < 0 or length > size ().
另请参阅 mid (), left (), right (), chopped ()，和 chop ().
Returns a const pointer to the first character in the string.
storage_type
is
char16_t
.
注意： The character array represented by the return value is not null-terminated.
另请参阅 begin (), end ()，和 data ().
返回字符位于位置 n 在此字符串视图。
行为未定义若 n is negative or not less than size ().
另请参阅 at (), front ()，和 back ().
返回哈希值为 key ，使用 seed 做计算种子。
该函数在 Qt 5.10 引入。