QStringView Class | Qt Core 6.4.3

- Qt 6.4
- Qt Core
- C++ Classes
- QStringView
- Qt 6.4.3 Reference Documentation

# QStringView Class

The QStringView class provides a unified view on UTF-16 strings with a read-only subset of the QString API. More...

Header: | #include <QStringView>
CMake: | find_package(Qt6 REQUIRED COMPONENTS Core) target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake: | QT += core
Since: | Qt 5.10

- List of all members, including inherited members
- Deprecated members

Note: All functions in this class are reentrant.

## Public Types

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

## Public Functions

| QStringView(const Container &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
const_iterator | begin() const
const_iterator | cbegin() const
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(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
int | compare(QChar ch) const
int | compare(QChar ch, Qt::CaseSensitivity cs) const
const_iterator | constBegin() const
const_pointer | constData() const
const_iterator | constEnd() const
bool | contains(QChar c, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
bool | contains(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
bool | contains(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
bool | contains(const QRegularExpression &re, QRegularExpressionMatch *rmatch = nullptr) const
qsizetype | count(const QRegularExpression &re) const
qsizetype | count(QChar ch, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | count(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | count(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
const_reverse_iterator | crbegin() const
const_reverse_iterator | crend() const
const_pointer | data() const
bool | empty() const
const_iterator | end() const
bool | endsWith(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
bool | endsWith(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
bool | endsWith(QChar ch) const
bool | endsWith(QChar ch, Qt::CaseSensitivity cs) const
QStringView | first(qsizetype n) 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(QLatin1StringView l1, qsizetype from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | indexOf(const QRegularExpression &re, qsizetype from = 0, QRegularExpressionMatch *rmatch = nullptr) const
bool | isEmpty() const
bool | isNull() const
bool | isRightToLeft() const
bool | isValidUtf16() const
QStringView | last(qsizetype n) const
QChar | last() const
qsizetype | lastIndexOf(QChar c, qsizetype from, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | lastIndexOf(QChar c, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | lastIndexOf(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | lastIndexOf(QStringView str, qsizetype from, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | lastIndexOf(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | lastIndexOf(QLatin1StringView l1, qsizetype from, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | lastIndexOf(const QRegularExpression &re, QRegularExpressionMatch *rmatch = nullptr) const
qsizetype | lastIndexOf(const QRegularExpression &re, qsizetype from, QRegularExpressionMatch *rmatch = nullptr) const
qsizetype | length() const
int | localeAwareCompare(QStringView other) const
const_reverse_iterator | rbegin() const
const_reverse_iterator | rend() const
qsizetype | size() const
QStringView | sliced(qsizetype pos, qsizetype n) const
QStringView | sliced(qsizetype pos) const
QList<QStringView> | split(QStringView sep, Qt::SplitBehavior behavior = Qt::KeepEmptyParts, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
QList<QStringView> | split(QChar sep, Qt::SplitBehavior behavior = Qt::KeepEmptyParts, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
QList<QStringView> | split(const QRegularExpression &re, Qt::SplitBehavior behavior = Qt::KeepEmptyParts) const
bool | startsWith(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
bool | startsWith(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
bool | startsWith(QChar ch) const
bool | startsWith(QChar ch, Qt::CaseSensitivity cs) const
CFStringRef | toCFString() const
double | toDouble(bool *ok = nullptr) const
float | toFloat(bool *ok = nullptr) const
int | toInt(bool *ok = nullptr, int base = 10) const
QByteArray | toLatin1() const
QByteArray | toLocal8Bit() const
long | toLong(bool *ok = nullptr, int base = 10) const
qlonglong | toLongLong(bool *ok = nullptr, int base = 10) const
NSString * | toNSString() const
short | toShort(bool *ok = nullptr, int base = 10) const
QString | toString() const
uint | toUInt(bool *ok = nullptr, int base = 10) const
ulong | toULong(bool *ok = nullptr, int base = 10) const
qulonglong | toULongLong(bool *ok = nullptr, int base = 10) const
ushort | toUShort(bool *ok = nullptr, int base = 10) const
QList<uint> | toUcs4() const
QByteArray | toUtf8() const
qsizetype | toWCharArray(wchar_t *array) const
decltype(qTokenize(*this, std::forward<Needle>(needle), flags...)) | tokenize(Needle &&sep, Flags... flags) const
QStringView | trimmed() const
void | truncate(qsizetype length)
const storage_type * | utf16() const
QChar | operator[](qsizetype n) const

## Static Public Members

QStringView | fromArray(const Char (&)[Size] string = Size)

## Related Non-Members

size_t | qHash(QStringView key, size_t seed = 0)
bool | operator!=(QStringView lhs, QStringView rhs)
bool | operator<(QStringView lhs, QStringView rhs)
bool | operator<=(QStringView lhs, QStringView rhs)
bool | operator==(QStringView lhs, QStringView rhs)
bool | operator>(QStringView lhs, QStringView rhs)
bool | operator>=(QStringView lhs, QStringView rhs)

## Detailed Description

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 first.

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 and `(const QChar*, qsizetype)`), while at the same time enabling even more string data sources to be passed to the function, such as `u"Hello World"`, a `char16_t` string literal.

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

- QChar: this overload can delegate to the QStringView version:

           void fun(QChar ch) { fun(QStringView(&ch, 1)); }

  even though, for technical reasons, QStringView cannot provide a QChar constructor by itself.

- QString: if you store an unmodified copy of the string and thus would like to take advantage of QString's implicit sharing.
- QLatin1StringView: if you can implement the function without converting the QLatin1StringView to UTF-16 first; users expect a function overloaded on QLatin1StringView to perform strictly less memory allocations than the semantically equivalent call of the QStringView version, involving construction of a QString from the QLatin1StringView.

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() in `constexpr` contexts instead.

See also QString.

## Member Type Documentation

### QStringView::const_iterator

This typedef provides an STL-style const iterator for QStringView.

See also iterator and const_reverse_iterator.

### QStringView::const_pointer

Alias for `value_type *`. Provided for compatibility with the STL.

### QStringView::const_reference

Alias for `value_type &`. Provided for compatibility with the STL.

### QStringView::const_reverse_iterator

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

See also reverse_iterator and const_iterator.

### QStringView::difference_type

Alias for `std::ptrdiff_t`. Provided for compatibility with the STL.

### QStringView::iterator

This typedef provides an STL-style const iterator for QStringView.

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

See also const_iterator and reverse_iterator.

### QStringView::pointer

Alias for `value_type *`. Provided for compatibility with the STL.

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

### QStringView::reference

Alias for `value_type &`. Provided for compatibility with the STL.

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

### QStringView::reverse_iterator

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.

See also const_reverse_iterator and iterator.

### QStringView::size_type

Alias for qsizetype. Provided for compatibility with the STL.

### QStringView::storage_type

Alias for `char16_t`.

### QStringView::value_type

Alias for `const QChar`. Provided for compatibility with the STL.

## Member Function Documentation

### `[since 6.0]` template <typename Needle, typename Flags> decltype(qTokenize(*this, std::forward<Needle>(needle), flags...)) QStringView::tokenize(Needle &&sep, Flags... flags) const

Splits the string into substring views wherever sep occurs, and returns a lazy sequence of those strings.

Equivalent to

     return QStringTokenizer{std::forward<Needle>(sep), flags...};

except it works without C++17 Class Template Argument Deduction (CTAD) enabled in the compiler.

See QStringTokenizer for how sep and flags interact to form the result.

Note: While this function returns QStringTokenizer, you should never, ever, name its template arguments explicitly. If you can use C++17 Class Template Argument Deduction (CTAD), you may write

     QStringTokenizer result = sv.tokenize(sep);

(without template arguments). If you can't use C++17 CTAD, you must store the return value only in `auto` variables:

     auto result = sv.tokenize(sep);

This is because the template arguments of QStringTokenizer have a very subtle dependency on the specific tokenize() overload from which they are returned, and they don't usually correspond to the type used for the separator.

This function was introduced in Qt 6.0.

See also QStringTokenizer and qTokenize().

### `[since 6.2]` qsizetype QStringView::lastIndexOf(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### `[since 6.2]` qsizetype QStringView::lastIndexOf(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads lastIndexOf().

Returns the index position of the last occurrence of the string view str or Latin-1 string l1, respectively, in this string view, searching backward from the last character of this string view. Returns -1 if str is not found.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 6.2.

See also QString::lastIndexOf().

### `[since 5.14]` qsizetype QStringView::lastIndexOf(QChar c, qsizetype from, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### `[since 5.14]` qsizetype QStringView::lastIndexOf(QLatin1StringView l1, qsizetype from, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### `[since 5.14]` qsizetype QStringView::lastIndexOf(QStringView str, qsizetype from, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

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. If from is -1, the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if str is not found.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

Note: When searching for a 0-length str or l1, the match at the end of the data is excluded from the search by a negative from, even though `-1` is normally thought of as searching from the end of the string view: the match at the end is after the last character, so it is excluded. To include such a final empty match, either give a positive value for from or omit the from parameter entirely.

This function was introduced in Qt 5.14.

See also QString::lastIndexOf().

### `[since 5.14]` bool QStringView::contains(QChar c, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### `[since 5.14]` bool QStringView::contains(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### `[since 5.14]` bool QStringView::contains(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns `true` if this string view contains an occurrence of the string view str, Latin-1 string l1, or character ch; otherwise returns `false`.

If cs is Qt::CaseSensitive (the default), the search is case-sensitive; otherwise the search is case-insensitive.

This function was introduced in Qt 5.14.

See also indexOf().

### `[since 5.14]` qsizetype QStringView::indexOf(QChar c, qsizetype from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### `[since 5.14]` qsizetype QStringView::indexOf(QLatin1StringView l1, qsizetype from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### `[since 5.14]` qsizetype QStringView::indexOf(QStringView str, qsizetype from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

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 is not found.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

If from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.

This function was introduced in Qt 5.14.

See also QString::indexOf().

### bool QStringView::endsWith(QChar ch) const

### bool QStringView::endsWith(QChar ch, Qt::CaseSensitivity cs) const

### bool QStringView::endsWith(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### bool QStringView::endsWith(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns `true` if this string view ends with string view str, Latin-1 string l1, or character ch, respectively; otherwise returns `false`.

If cs is Qt::CaseSensitive (the default), the search is case-sensitive; otherwise the search is case-insensitive.

See also startsWith().

### bool QStringView::startsWith(QChar ch) const

### bool QStringView::startsWith(QChar ch, Qt::CaseSensitivity cs) const

### bool QStringView::startsWith(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### bool QStringView::startsWith(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns `true` if this string view starts with string view str, Latin-1 string l1, or character ch, respectively; otherwise returns `false`.

If cs is Qt::CaseSensitive (the default), the search is case-sensitive; otherwise the search is case-insensitive.

See also endsWith().

### `[since 5.15]` int QStringView::compare(QChar ch) const

### `[since 5.15]` int QStringView::compare(QChar ch, Qt::CaseSensitivity cs) const

### `[since 5.15]` int QStringView::compare(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns an integer that compares to zero as this string view compares to the Latin-1 string l1, or character ch, respectively.

If cs is Qt::CaseSensitive (the default), the comparison is case sensitive; otherwise the comparison is case-insensitive.

This function was introduced in Qt 5.15.

See also operator==(), operator<(), and operator>().

### `[since 5.14]` template <typename Args> QString QStringView::arg(Args &&... args) const

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 QLatin1StringView.

In addition, the following types are also supported: QChar, QLatin1Char.

This function was introduced in Qt 5.14.

See also QString::arg().

### `[since 6.0]` QList<QStringView> QStringView::split(QChar sep, Qt::SplitBehavior behavior = Qt::KeepEmptyParts, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### `[since 6.0]` QList<QStringView> QStringView::split(QStringView sep, Qt::SplitBehavior behavior = Qt::KeepEmptyParts, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Splits the view into substring views wherever sep occurs, and returns the list of those string views.

See QString::split() for how sep, behavior and cs interact to form the result.

Note: All the returned views are valid as long as the data referenced by this string view is valid. Destroying the data will cause all views to become dangling.

This function was introduced in Qt 6.0.

### template <typename Container, if_compatible_container<Container>> QStringView::QStringView(const Container &str)

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).

See also isNull() and isEmpty().

### QStringView::QStringView(const QString &str)

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()`.

### template <typename Char> QStringView::QStringView(const Char *str)

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.

Passing `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`.

### template <typename Char, size_t N> QStringView::QStringView(const Char (&)[N] string = N)

Constructs a string view on the character string literal 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() instead.

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`.

See also fromArray.

### template <typename Char, if_compatible_char<Char>> QStringView::QStringView(const Char *first, const Char *last)

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.

Passing `\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, or 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`.

### template <typename Char, if_compatible_char<Char>> QStringView::QStringView(const Char *str, qsizetype len)

Constructs a string view on str with length len.

The range `[str,len)` must remain valid for the lifetime of this string view object.

Passing `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`.

### QStringView::QStringView(std::nullptr_t)

Constructs a null string view.

See also isNull().

### QStringView::QStringView()

Constructs a null string view.

See also isNull().

### QChar QStringView::at(qsizetype n) const

Returns the character at position n in this string view.

The behavior is undefined if n is negative or not less than size().

See also operator[](), front(), and back().

### QChar QStringView::back() const

Returns the last character in the string view. Same as last().

This function is provided for STL compatibility.

Warning: Calling this function on an empty string view constitutes undefined behavior.

See also front(), first(), and last().

### const_iterator QStringView::begin() const

Returns a const STL-style iterator pointing to the first character in the string view.

This function is provided for STL compatibility.

See also end(), constBegin(), cbegin(), rbegin(), and data().

### const_iterator QStringView::cbegin() const

Same as begin().

This function is provided for STL compatibility.

See also cend(), begin(), constBegin(), crbegin(), and data().

### const_iterator QStringView::cend() const

Same as end().

This function is provided for STL compatibility.

See also cbegin(), end(), constEnd(), and crend().

### void QStringView::chop(qsizetype length)

Truncates this string view by length characters.

Same as `*this = left(size() - length)`.

Note: The behavior is undefined when length < 0 or length > size().

See also mid(), left(), right(), chopped(), and truncate().

### QStringView QStringView::chopped(qsizetype length) const

Returns the substring of length size() - length starting at the beginning of this object.

Same as `left(size() - length)`.

Note: The behavior is undefined when length < 0 or length > size().

See also mid(), left(), right(), chop(), and truncate().

### `[since 5.12]` int QStringView::compare(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns an integer that compares to zero as this string view compares to the string view str.

If cs is Qt::CaseSensitive (the default), the comparison is case sensitive; otherwise the comparison is case-insensitive.

This function was introduced in Qt 5.12.

See also operator==(), operator<(), and operator>().

### `[since 6.1]` const_iterator QStringView::constBegin() const

Same as begin().

This function was introduced in Qt 6.1.

See also constEnd(), begin(), cbegin(), crbegin(), and data().

### `[since 6.0]` const_pointer QStringView::constData() const

Returns a const pointer to the first character in the string view.

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

This function was introduced in Qt 6.0.

See also data(), begin(), end(), and utf16().

### `[since 6.1]` const_iterator QStringView::constEnd() const

Same as end().

This function was introduced in Qt 6.1.

See also constBegin(), end(), cend(), and crend().

### `[since 6.1]` bool QStringView::contains(const QRegularExpression &re, QRegularExpressionMatch *rmatch = nullptr) const

Returns `true` if the regular expression re matches somewhere in this string view; otherwise returns `false`.

If the match is successful and rmatch is not `nullptr`, it also writes the results of the match into the QRegularExpressionMatch object pointed to by rmatch.

This function was introduced in Qt 6.1.

See also QRegularExpression::match().

### `[since 6.1]` qsizetype QStringView::count(const QRegularExpression &re) const

Returns the number of times the regular expression re matches in the string view.

For historical reasons, this function counts overlapping matches. This behavior is different from simply iterating over the matches in the string view using QRegularExpressionMatchIterator.

This function was introduced in Qt 6.1.

See also QRegularExpression::globalMatch().

### `[since 6.0]` qsizetype QStringView::count(QChar ch, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads count().

Returns the number of occurrences of the character ch in the string view.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 6.0.

See also QString::count(), contains(), and indexOf().

### `[since 6.0]` qsizetype QStringView::count(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads count().

Returns the number of (potentially overlapping) occurrences of the string view str in this string view.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 6.0.

See also QString::count(), contains(), and indexOf().

### `[since 6.4]` qsizetype QStringView::count(QLatin1StringView l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads count().

Returns the number of (potentially overlapping) occurrences of the Latin-1 string l1 in this string view.

If cs is Qt::CaseSensitive (default), the search is case sensitive; otherwise the search is case insensitive.

This function was introduced in Qt 6.4.

See also QString::count(), contains(), and indexOf().

### const_reverse_iterator QStringView::crbegin() const

Same as rbegin().

This function is provided for STL compatibility.

See also crend(), rbegin(), and cbegin().

### const_reverse_iterator QStringView::crend() const

Same as rend().

This function is provided for STL compatibility.

See also crbegin(), rend(), and cend().

### const_pointer QStringView::data() const

Returns a const pointer to the first character in the string view.

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

See also begin(), end(), and utf16().

### bool QStringView::empty() const

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

This function is provided for STL compatibility.

See also isEmpty(), isNull(), size(), and length().

### const_iterator QStringView::end() const

Returns a const STL-style iterator pointing to the imaginary character after the last character in the list.

This function is provided for STL compatibility.

See also begin(), constEnd(), cend(), and rend().

### `[since 6.0]` QStringView QStringView::first(qsizetype n) const

Returns a string view that points to the first n characters of this string view.

Note: The behavior is undefined when n < 0 or n > size().

This function was introduced in Qt 6.0.

See also last(), sliced(), startsWith(), chopped(), chop(), and truncate().

### QChar QStringView::first() const

Returns the first character in the string view. Same as front().

This function is provided for compatibility with other Qt containers.

Warning: Calling this function on an empty string view constitutes undefined behavior.

See also front(), back(), and last().

### `[static]` template <typename Char, size_t Size, if_compatible_char<Char>> QStringView QStringView::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 must remain valid for the lifetime of this string view object.

This function will work with any array literal 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`.

### QChar QStringView::front() const

Returns the first character in the string view. Same as first().

This function is provided for STL compatibility.

Warning: Calling this function on an empty string view constitutes undefined behavior.

See also back(), first(), and last().

### `[since 6.1]` qsizetype QStringView::indexOf(const QRegularExpression &re, qsizetype from = 0, QRegularExpressionMatch *rmatch = nullptr) const

Returns the index position of the first match of the regular expression re in the string view, searching forward from index position from. Returns -1 if re didn't match anywhere.

If the match is successful and rmatch is not `nullptr`, it also writes the results of the match into the QRegularExpressionMatch object pointed to by rmatch.

Note: Due to how the regular expression matching algorithm works, this function will actually match repeatedly from the beginning of the string view until the position from is reached.

This function was introduced in Qt 6.1.

### bool QStringView::isEmpty() const

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

This function is provided for compatibility with other Qt containers.

See also empty(), isNull(), size(), and length().

### bool QStringView::isNull() const

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

This functions is provided for compatibility with other Qt containers.

See also empty(), isEmpty(), size(), and length().

### `[since 5.11]` bool QStringView::isRightToLeft() const

Returns `true` if the string view is read right to left.

This function was introduced in Qt 5.11.

See also QString::isRightToLeft().

### `[since 5.15]` bool QStringView::isValidUtf16() const

Returns `true` if the string view contains valid UTF-16 encoded data, or `false` otherwise.

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.

This function was introduced in Qt 5.15.

See also QString::isValidUtf16().

### `[since 6.0]` QStringView QStringView::last(qsizetype n) const

Returns a string view that points to the last n characters of this string view.

Note: The behavior is undefined when n < 0 or n > size().

This function was introduced in Qt 6.0.

See also first(), sliced(), endsWith(), chopped(), chop(), and truncate().

### QChar QStringView::last() const

Returns the last character in the string view. Same as back().

This function is provided for compatibility with other Qt containers.

Warning: Calling this function on an empty string view constitutes undefined behavior.

See also back(), front(), and first().

### `[since 6.3]` qsizetype QStringView::lastIndexOf(QChar c, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This function overloads lastIndexOf().

This function was introduced in Qt 6.3.

### `[since 6.2]` qsizetype QStringView::lastIndexOf(const QRegularExpression &re, QRegularExpressionMatch *rmatch = nullptr) const

Returns the index position of the last match of the regular expression re in the string view. Returns -1 if re didn't match anywhere.

If the match is successful and rmatch is not `nullptr`, it also writes the results of the match into the QRegularExpressionMatch object pointed to by rmatch.

Note: Due to how the regular expression matching algorithm works, this function will actually match repeatedly from the beginning of the string view until the end of the string view is reached.

This function was introduced in Qt 6.2.

### `[since 6.1]` qsizetype QStringView::lastIndexOf(const QRegularExpression &re, qsizetype from, QRegularExpressionMatch *rmatch = nullptr) const

Returns the index position of the last match of the regular expression re in the string view, which starts before the index position from. If from is -1, the search starts at the last character; if from is -2, at the next to last character and so on. Returns -1 if re didn't match anywhere.

If the match is successful and rmatch is not `nullptr`, it also writes the results of the match into the QRegularExpressionMatch object pointed to by rmatch.

Note: Due to how the regular expression matching algorithm works, this function will actually match repeatedly from the beginning of the string view until the position from is reached.

Note: When searching for a regular expression re that may match 0 characters, the match at the end of the data is excluded from the search by a negative from, even though `-1` is normally thought of as searching from the end of the string view: the match at the end is after the last character, so it is excluded. To include such a final empty match, either give a positive value for from or omit the from parameter entirely.

This function was introduced in Qt 6.1.

### qsizetype QStringView::length() const

Same as size().

This function is provided for compatibility with other Qt containers.

See also empty(), isEmpty(), isNull(), and size().

### `[since 6.4]` int QStringView::localeAwareCompare(QStringView other) const

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.

The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.

This function was introduced in Qt 6.4.

See also Comparing Strings.

### const_reverse_iterator QStringView::rbegin() const

Returns a const STL-style reverse iterator pointing to the first character in the string view, in reverse order.

This function is provided for STL compatibility.

See also rend(), crbegin(), and begin().

### const_reverse_iterator QStringView::rend() const

Returns a STL-style reverse iterator pointing to one past the last character in the string view, in reverse order.

This function is provided for STL compatibility.

See also rbegin(), crend(), and end().

### qsizetype QStringView::size() const

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).

See also empty(), isEmpty(), isNull(), and length().

### `[since 6.0]` QStringView QStringView::sliced(qsizetype pos, qsizetype n) const

Returns a string view that points to n characters of this string view, starting at position pos.

Note: The behavior is undefined when pos < 0, n < 0, or pos + n > size().

This function was introduced in Qt 6.0.

See also first(), last(), chopped(), chop(), and truncate().

### `[since 6.0]` QStringView QStringView::sliced(qsizetype pos) const

This is an overloaded function.

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

Note: The behavior is undefined when pos < 0 or pos > size().

This function was introduced in Qt 6.0.

See also first(), last(), chopped(), chop(), and truncate().

### `[since 6.0]` QList<QStringView> QStringView::split(const QRegularExpression &re, Qt::SplitBehavior behavior = Qt::KeepEmptyParts) const

Splits the string into substring views wherever the regular expression re matches, and returns the list of those strings. If re does not match anywhere in the string, split() returns a single-element list containing this string as view.

Note: The views in the returned list are sub-views of this view; as such, they reference the same data as it and only remain valid for as long as that data remains live.

This function was introduced in Qt 6.0.

### `[since 6.0]` CFStringRef QStringView::toCFString() const

Creates a CFString from this QStringView.

The caller owns the CFString and is responsible for releasing it.

Note: this function is only available on macOS and iOS.

This function was introduced in Qt 6.0.

### `[since 6.0]` double QStringView::toDouble(bool *ok = nullptr) const

Returns the string view converted to a `double` value.

Returns an infinity if the conversion overflows or 0.0 if the conversion fails for other reasons (e.g. underflow).

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toDouble()

For historic reasons, this function does not handle thousands group separators. If you need to convert such numbers, use QLocale::toDouble().

This function was introduced in Qt 6.0.

See also QString::toDouble().

### `[since 6.0]` float QStringView::toFloat(bool *ok = nullptr) const

Returns the string view converted to a `float` value.

Returns an infinity if the conversion overflows or 0.0 if the conversion fails for other reasons (e.g. underflow).

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toFloat()

This function was introduced in Qt 6.0.

See also QString::toFloat().

### `[since 6.0]` int QStringView::toInt(bool *ok = nullptr, int base = 10) const

Returns the string view converted to an `int` using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

If base is 0, the C language convention is used: if the string view begins with "0x", base 16 is used; otherwise, if the string view begins with "0", base 8 is used; otherwise, base 10 is used.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toInt()

This function was introduced in Qt 6.0.

See also QString::toInt().

### QByteArray QStringView::toLatin1() const

Returns a Latin-1 representation of the string as a QByteArray.

The behavior is undefined if the string contains non-Latin1 characters.

See also toUtf8(), toLocal8Bit(), and QStringEncoder.

### QByteArray QStringView::toLocal8Bit() const

Returns a local 8-bit representation of the string as a QByteArray.

On Unix systems this is equivalen to toUtf8(), on Windows the systems current code page is being used.

The behavior is undefined if the string contains characters not supported by the locale's 8-bit encoding.

See also toLatin1(), toUtf8(), and QStringEncoder.

### `[since 6.0]` long QStringView::toLong(bool *ok = nullptr, int base = 10) const

Returns the string view converted to a `long` using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

If base is 0, the C language convention is used: if the string view begins with "0x", base 16 is used; otherwise, if the string view begins with "0", base 8 is used; otherwise, base 10 is used.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toLong()

This function was introduced in Qt 6.0.

See also QString::toLong().

### `[since 6.0]` qlonglong QStringView::toLongLong(bool *ok = nullptr, int base = 10) const

Returns the string view converted to a `long long` using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

If base is 0, the C language convention is used: if the string view begins with "0x", base 16 is used; otherwise, if the string view begins with "0", base 8 is used; otherwise, base 10 is used.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toLongLong()

This function was introduced in Qt 6.0.

See also QString::toLongLong().

### `[since 6.0]` NSString *QStringView::toNSString() const

Creates an NSString from this QStringView.

The NSString is autoreleased.

Note: this function is only available on macOS and iOS.

This function was introduced in Qt 6.0.

### `[since 6.0]` short QStringView::toShort(bool *ok = nullptr, int base = 10) const

Returns the string view converted to a `short` using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

If base is 0, the C language convention is used: if the string view begins with "0x", base 16 is used; otherwise, if the string view begins with "0", base 8 is used; otherwise, base 10 is used.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toShort()

This function was introduced in Qt 6.0.

See also QString::toShort().

### QString QStringView::toString() const

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.

### `[since 6.0]` uint QStringView::toUInt(bool *ok = nullptr, int base = 10) const

Returns the string view converted to an `unsigned int` using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

If base is 0, the C language convention is used: if the string view begins with "0x", base 16 is used; otherwise, if the string view begins with "0", base 8 is used; otherwise, base 10 is used.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toUInt()

This function was introduced in Qt 6.0.

See also QString::toUInt().

### `[since 6.0]` ulong QStringView::toULong(bool *ok = nullptr, int base = 10) const

Returns the string view converted to an `unsigned long` using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

If base is 0, the C language convention is used: if the string view begins with "0x", base 16 is used; otherwise, if the string view begins with "0", base 8 is used; otherwise, base 10 is used.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toULongLong()

This function was introduced in Qt 6.0.

See also QString::toULong().

### `[since 6.0]` qulonglong QStringView::toULongLong(bool *ok = nullptr, int base = 10) const

Returns the string view converted to an `unsigned long long` using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

If base is 0, the C language convention is used: if the string view begins with "0x", base 16 is used; otherwise, if the string view begins with "0", base 8 is used; otherwise, base 10 is used.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toULongLong()

This function was introduced in Qt 6.0.

See also QString::toULongLong().

### `[since 6.0]` ushort QStringView::toUShort(bool *ok = nullptr, int base = 10) const

Returns the string view converted to an `unsigned short` using base base, which is 10 by default and must be between 2 and 36, or 0. Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

If base is 0, the C language convention is used: if the string view begins with "0x", base 16 is used; otherwise, if the string view begins with "0", base 8 is used; otherwise, base 10 is used.

The string conversion will always happen in the 'C' locale. For locale dependent conversion use QLocale::toUShort()

This function was introduced in Qt 6.0.

See also QString::toUShort().

### QList<uint> QStringView::toUcs4() const

Returns a UCS-4/UTF-32 representation of the string view as a QList<uint>.

UCS-4 is a Unicode codec and therefore it is lossless. All characters from this string view will be encoded in UCS-4. Any invalid sequence of code units in this string view is replaced by the Unicode replacement character (QChar::ReplacementCharacter, which corresponds to `U+FFFD`).

The returned list is not 0-terminated.

See also toUtf8(), toLatin1(), toLocal8Bit(), and QStringEncoder.

### QByteArray QStringView::toUtf8() const

Returns a UTF-8 representation of the string view as a QByteArray.

UTF-8 is a Unicode codec and can represent all characters in a Unicode string like QString.

See also toLatin1(), toLocal8Bit(), and QStringEncoder.

### `[since 5.14]` qsizetype QStringView::toWCharArray(wchar_t *array) const

Transcribes this string view into the given array.

The caller is responsible for ensuring array is large enough to hold the `wchar_t` encoding of this string view (allocating the array with the same length as the string view 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.

Note: This function writes no null terminator to the end of array.

Returns the number of `wchar_t` entries written to array.

This function was introduced in Qt 5.14.

See also QString::toWCharArray().

### QStringView QStringView::trimmed() const

Strips leading and trailing whitespace and returns the result.

Whitespace means any character for which QChar::isSpace() returns `true`. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.

### void QStringView::truncate(qsizetype length)

Truncates this string view to length length.

Same as `*this = left(length)`.

Note: The behavior is undefined when length < 0 or length > size().

See also mid(), left(), right(), chopped(), and chop().

### const storage_type *QStringView::utf16() const

Returns a const pointer to the first character in the string view.

`storage_type` is `char16_t`.

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

See also begin(), end(), and data().

### QChar QStringView::operator[](qsizetype n) const

Returns the character at position n in this string view.

The behavior is undefined if n is negative or not less than size().

See also at(), front(), and back().

## Related Non-Members

### bool operator!=(QStringView lhs, QStringView rhs)

### bool operator<(QStringView lhs, QStringView rhs)

### bool operator<=(QStringView lhs, QStringView rhs)

### bool operator==(QStringView lhs, QStringView rhs)

### bool operator>(QStringView lhs, QStringView rhs)

### bool operator>=(QStringView lhs, QStringView rhs)

Operators for comparing lhs to rhs.

See also compare().

### `[since 5.10]` size_t qHash(QStringView key, size_t seed = 0)

Returns the hash value for the key, using seed to seed the calculation.

This function was introduced in Qt 5.10.