QStringView 类提供 UTF-16 字符串统一视图，采用只读子集的 QString API. 更多...
| 头： | #include <QStringView> |
| qmake: | QT += core |
| Since: | Qt 5.10 |
该类在 Qt 5.10 引入。
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 (const StdBasicString & str ) | |
| QStringView (const QStringRef & str ) | |
| QStringView (const QString & str ) | |
| QStringView (const Char * str ) | |
| QStringView (const Char (&)[N] string = N) | |
| QStringView (const Char * first , const Char * last ) | |
| QStringView (const Char * str , qsizetype len ) | |
| QStringView ( std::nullptr_t ) | |
| QStringView () | |
| QString | arg (Args &&... args ) const |
| 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 str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| int | compare (QLatin1String l1 , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| int | compare (QChar ch ) const |
| int | compare (QChar ch , Qt::CaseSensitivity cs ) const |
| bool | contains (QChar c , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| bool | contains (QStringView str , Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| bool | contains (QLatin1String l1 , 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 |
| qsizetype | indexOf (QChar c , qsizetype from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| qsizetype | indexOf (QStringView str , qsizetype from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| qsizetype | indexOf (QLatin1String l1 , qsizetype from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| bool | isEmpty () const |
| bool | isNull () const |
| bool | isRightToLeft () const |
| bool | isValidUtf16 () const |
| QChar | last () const |
| qsizetype | lastIndexOf (QChar c , qsizetype from = -1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| qsizetype | lastIndexOf (QStringView str , qsizetype from = -1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const |
| qsizetype | lastIndexOf (QLatin1String l1 , qsizetype from = -1, Qt::CaseSensitivity cs = Qt::CaseSensitive) 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 |
| int | toWCharArray (wchar_t * array ) 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 = 0) |
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
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 into a QString .
QStringView is a
Literal Type
, 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 .
This typedef provides an STL-style const iterator for QStringView .
另请参阅 iterator and const_reverse_iterator .
别名化的
value_type *
. Provided for compatibility with the STL.
别名化的
value_type &
. Provided for compatibility with the STL.
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
. Provided for compatibility with the STL.
This typedef provides an STL-style const iterator for 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 *
. Provided for compatibility with the STL.
QStringView does not support mutable pointers, so this is the same as const_pointer .
别名化的
value_type &
. Provided for compatibility with the STL.
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 .
Alias for qsizetype. Provided for compatibility with the STL.
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
.
别名化的
const QChar
. Provided for compatibility with the STL.
Returns the index position of the last occurrence of the string-view str , Latin-1 string l1 , or character ch , respectively, in this string-view, searching backward from index position from 。若 from is -1 (default), the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str 找不到。
若 cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.
该函数在 Qt 5.14 引入。
另请参阅 QString::lastIndexOf ().
返回
true
if this string-view contains an occurrence of the string-view
str
, Latin-1 string
l1
, or character
ch
；否则返回
false
.
若 cs is Qt::CaseSensitive (the default), the search is case-sensitive; otherwise the search is case-insensitive.
该函数在 Qt 5.14 引入。
另请参阅 indexOf ().
Returns the index position of the first occurrence of the string-view str , Latin-1 string l1 , or character ch , respectively, in this string-view, searching forward from index position from . Returns -1 if str 找不到。
若 cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.
若 from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.
该函数在 Qt 5.14 引入。
另请参阅 QString::indexOf ().
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 (the default), the search is case-sensitive; otherwise the search is case-insensitive.
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 (the default), the search is case-sensitive; otherwise the search is case-insensitive.
另请参阅 endsWith ().
Returns an integer that compares to zero as this string-view compares to the Latin-1 string l1 , or character ch ，分别。
若 cs is Qt::CaseSensitive (the default), the comparison is case sensitive; otherwise the comparison is case-insensitive.
该函数在 Qt 5.14 引入。
另请参阅 operator== (), operator< ()，和 operator> ().
Replaces occurrences of
%N
in this string with the corresponding argument from
args
. The arguments are not positional: the first of the
args
replaces the
%N
with the lowest
N
(all of them), the second of the
args
the
%N
with the next-lowest
N
etc.
Args
can consist of anything that implicitly converts to
QString
,
QStringView
or
QLatin1String
.
In addition, the following types are also supported: QChar , QLatin1Char .
该函数在 Qt 5.14 引入。
另请参阅 QString::arg ().
Constructs a string view on
str
. The length is taken from
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).
Constructs a string view on str .
str.data()
must remain valid for the lifetime of this string view object.
The string view will be null if and only if
str.isNull()
.
Constructs a string view on str .
str.data()
must remain valid for the lifetime of this string view object.
The string view will be null if and only if
str.isNull()
.
Constructs a string view on
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
is safe and results in a null string view.
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
.
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
.
Constructs a string view on first with length ( last - first ).
The range
[first,last)
must remain valid for the lifetime of this string view object.
传递
\nullptr
as
first
is safe if
last
is
nullptr
, too, and results in a null string view.
The behavior is undefined if
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 str with length len .
The range
[str,len)
must remain valid for the lifetime of this string view object.
传递
nullptr
as
str
is safe if
len
is 0, too, and results in a null string view.
The behavior is undefined if
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
.
Constructs a null string view.
另请参阅 isNull ().
Constructs a null string view.
另请参阅 isNull ().
返回字符位于位置 n in this string view.
The behavior is undefined if n is negative or not less than size ().
另请参阅 operator[] (), front ()，和 back ().
Returns the last character in the string. Same as last ().
This function is provided for STL compatibility.
警告： Calling this function on an empty string view constitutes undefined behavior.
另请参阅 front (), first ()，和 last ().
返回常量 STL 样式迭代器 pointing to the first character in the string.
This function is provided for STL compatibility.
另请参阅 end (), cbegin (), rbegin ()，和 data ().
如同 begin ().
This function is provided for STL compatibility.
另请参阅 cend (), begin (), crbegin ()，和 data ().
如同 end ().
This function is provided for STL compatibility.
另请参阅 cbegin (), end ()，和 crend ().
Truncates this string view by length 字符。
如同
*this = left(size() - length)
.
注意： The behavior is undefined when length < 0 or length > size ().
另请参阅 mid (), left (), right (), chopped ()，和 truncate ().
Returns the substring of length size () - length starting at the beginning of this object.
如同
left(size() - length)
.
注意： The behavior is undefined when length < 0 or length > size ().
另请参阅 mid (), left (), right (), chop ()，和 truncate ().
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.
该函数在 Qt 5.12 引入。
另请参阅 operator== (), operator< ()，和 operator> ().
如同 rbegin ().
This function is provided for STL compatibility.
另请参阅 crend (), rbegin ()，和 cbegin ().
如同 rend ().
This function is provided for STL compatibility.
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
.
This function is provided for STL compatibility.
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.
This function is provided for STL compatibility.
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： Calling this function on an empty string view constitutes undefined behavior.
另请参阅 front (), back ()，和 last ().
Returns the first character in the string. Same as first ().
This function is provided for STL compatibility.
警告： Calling this function on an empty string view constitutes undefined behavior.
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
true
if the string contains valid UTF-16 encoded data, or
false
否则。
Note that this function does not perform any special validation of the data; it merely checks if it can be successfully decoded from UTF-16. The data is assumed to be in host byte order; the presence of a BOM is meaningless.
该函数在 Qt 5.15 引入。
另请参阅 QString::isValidUtf16 ().
Returns the last character in the string. Same as back ().
This function is provided for compatibility with other Qt containers.
警告： Calling this function on an empty string view constitutes undefined behavior.
另请参阅 back (), front ()，和 first ().
Returns the substring of length length starting at position 0 in this object.
注意： The behavior is undefined when 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： The behavior is undefined when start < 0 or start > size ().
另请参阅 left (), right (), chopped (), chop ()，和 truncate ().
这是重载函数。
Returns the substring of length length starting at position start 在此对象。
注意： The behavior is undefined when 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.
This function is provided for STL compatibility.
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.
This function is provided for STL compatibility.
另请参阅 rbegin (), crend ()，和 end ().
Returns the substring of length length starting at position size () - length 在此对象。
注意： The behavior is undefined when 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 .
Transcribes this string into the given array .
The caller is responsible for ensuring
array
is large enough to hold the
wchar_t
encoding of this string (allocating the array with the same length as the string is always sufficient). The array is encoded in UTF-16 on platforms where
wchar_t
is 2 bytes wide (e.g. Windows); otherwise (Unix systems),
wchar_t
is assumed to be 4 bytes wide and the data is written in UCS-4.
注意： This function writes no null terminator to the end of array .
Returns the number of
wchar_t
entries written to
array
.
该函数在 Qt 5.14 引入。
另请参阅 QString::toWCharArray ().
Strips leading and trailing whitespace and returns the result.
Whitespace means any character for which
QChar::isSpace
() 返回
true
. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.
Truncates this string view to length length .
如同
*this = left(length)
.
注意： The behavior is undefined when 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 in this string view.
The behavior is undefined if 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。