- Qt 5.15
- Qt Core
- C++ Classes
- QStringView
- Qt 5.15.19 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>
qmake: | QT += core
Since: | Qt 5.10

This class was introduced in Qt 5.10.

- List of all members, including inherited members

Note: All functions in this class are reentrant.

## Public Types

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

## Public Functions

| 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
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(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
qsizetype | count(QChar ch, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
qsizetype | count(QStringView str, 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(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
const_reverse_iterator | rbegin() const
const_reverse_iterator | rend() const
QStringView | right(qsizetype length) const
qsizetype | size() 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 &sep, Qt::SplitBehavior behavior = Qt::KeepEmptyParts) 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
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
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
QVector<uint> | toUcs4() const
QByteArray | toUtf8() const
int | toWCharArray(wchar_t *array) const
QStringView | trimmed() const
void | truncate(qsizetype length)
const storage_type * | utf16() const
QChar | operator[](qsizetype n) const

## Related Non-Members

uint | qHash(QStringView key, uint seed = 0)

## 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, QStringRef, and `(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"`, 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.
- QLatin1String: if you can implement the function without converting the QLatin1String to UTF-16 first; users expect a function overloaded on QLatin1String to perform strictly less memory allocations than the semantically equivalent call of the QStringView version, involving construction of a QString from the QLatin1String.

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.

Note: 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.

See also QString and QStringRef.

## Member Type Documentation

### typedef QStringView::const_iterator

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

See also iterator and const_reverse_iterator.

### typedef QStringView::const_pointer

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

### typedef QStringView::const_reference

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

### typedef QStringView::const_reverse_iterator

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

See also reverse_iterator and const_iterator.

### typedef QStringView::difference_type

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

### typedef 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.

### typedef 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.

### typedef 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.

### typedef 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.

### typedef QStringView::size_type

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`.

### typedef QStringView::storage_type

Alias for `char16_t`.

### typedef QStringView::value_type

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

## Member Function Documentation

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

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

### QList<QStringView> QStringView::split(const QRegularExpression &sep, Qt::SplitBehavior behavior = Qt::KeepEmptyParts) const

Splits the string into substrings wherever sep occurs, and returns the list of those strings.

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

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

### qsizetype QStringView::lastIndexOf(QChar c, qsizetype from = -1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### qsizetype QStringView::lastIndexOf(QLatin1String l1, qsizetype from = -1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### qsizetype QStringView::lastIndexOf(QStringView str, qsizetype from = -1, 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 (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 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 5.14.

See also QString::lastIndexOf().

### bool QStringView::contains(QChar c, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### bool QStringView::contains(QLatin1String l1, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### 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().

### qsizetype QStringView::indexOf(QChar c, qsizetype from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### qsizetype QStringView::indexOf(QLatin1String l1, qsizetype from = 0, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

### 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(QLatin1String 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(QLatin1String 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().

### int QStringView::compare(QChar ch) const

### int QStringView::compare(QChar ch, Qt::CaseSensitivity cs) const

### int QStringView::compare(QLatin1String 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 5.14.

### 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 QLatin1String.

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

This function was introduced in Qt 5.14.

See also QString::arg().

### template <typename StdBasicString, if_compatible_string<StdBasicString>> QStringView::QStringView(const StdBasicString &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 QStringRef &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()`.

### 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 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`.

### 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. 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.

This function is provided for STL compatibility.

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

### const_iterator QStringView::cbegin() const

Same as begin().

This function is provided for STL compatibility.

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

### const_iterator QStringView::cend() const

Same as end().

This function is provided for STL compatibility.

See also cbegin(), end(), 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().

### 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.

### qsizetype QStringView::count(QChar ch, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

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

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

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

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

### qsizetype QStringView::count(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

This is an overloaded function.

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

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

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

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.

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(), cend(), and rend().

### QChar QStringView::first() const

Returns the first character in the string. 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().

### QChar QStringView::front() const

Returns the first character in the string. 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().

### 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().

### bool QStringView::isRightToLeft() const

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

This function was introduced in Qt 5.11.

See also QString::isRightToLeft().

### bool QStringView::isValidUtf16() const

Returns `true` if the string 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().

### QChar QStringView::last() const

Returns the last character in the string. 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().

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

Returns the substring of length length starting at position 0 in this object.

Note: Until 5.15.1, the behavior was undefined when length < 0 or length > size(). Since 5.15.2, the behavior is compatible with QString::left().

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

### int QStringView::length() const

Same as size(), except returns the result as an `int`.

This function is provided for compatibility with other Qt containers.

Warning: QStringView can represent strings with more than 231 characters. Calling this function on a string view for which size() returns a value greater than `INT_MAX` constitutes undefined behavior.

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

### QStringView QStringView::mid(qsizetype start) const

Returns the substring starting at position start in this object, and extending to the end of the string.

Note: Until 5.15.1, the behavior was undefined when start < 0 or start > size(). Since 5.15.2, the behavior is compatible with QString::mid().

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

### QStringView QStringView::mid(qsizetype start, qsizetype length) const

This is an overloaded function.

Returns the substring of length length starting at position start in this object.

Note: Until 5.15.1, the behavior was undefined when start < 0, length < 0, or start + length > size(). Since 5.15.2, the behavior is compatible with QString::mid().

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

### const_reverse_iterator QStringView::rbegin() const

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

This function is provided for STL compatibility.

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

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

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

Note: Until 5.15.1, the behavior was undefined when length < 0 or length > size(). Since 5.15.2, the behavior is compatible with QString::right().

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

### 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 and QStringRef).

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

### double QStringView::toDouble(bool *ok = nullptr) const

Returns the string 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().

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

See also QString::toDouble().

### float QStringView::toFloat(bool *ok = nullptr) const

Returns the string 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()

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

See also QString::toFloat().

### int QStringView::toInt(bool *ok = nullptr, int base = 10) const

Returns the string 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 begins with "0x", base 16 is used; if the string 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()

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

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 QTextCodec.

### QByteArray QStringView::toLocal8Bit() const

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.

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

### long QStringView::toLong(bool *ok = nullptr, int base = 10) const

Returns the string 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 begins with "0x", base 16 is used; if the string 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()

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

See also QString::toLong().

### qlonglong QStringView::toLongLong(bool *ok = nullptr, int base = 10) const

Returns the string 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 begins with "0x", base 16 is used; if the string 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()

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

See also QString::toLongLong().

### short QStringView::toShort(bool *ok = nullptr, int base = 10) const

Returns the string 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 begins with "0x", base 16 is used; if the string 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()

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

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.

Warning: QStringView can store strings with more than 230 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.

### uint QStringView::toUInt(bool *ok = nullptr, int base = 10) const

Returns the string 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 begins with "0x", base 16 is used; if the string 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()

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

See also QString::toUInt().

### ulong QStringView::toULong(bool *ok = nullptr, int base = 10) const

Returns the string 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 begins with "0x", base 16 is used; if the string 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()

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

See also QString::toULong().

### qulonglong QStringView::toULongLong(bool *ok = nullptr, int base = 10) const

Returns the string 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 begins with "0x", base 16 is used; if the string 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()

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

See also QString::toULongLong().

### ushort QStringView::toUShort(bool *ok = nullptr, int base = 10) const

Returns the string 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 begins with "0x", base 16 is used; if the string 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()

Note: This method has been added in 5.15.2 to simplify writing code that is portable between Qt 5.15 and Qt 6. The implementation is not tuned for performance in Qt 5.

This function was introduced in Qt 5.15.2.

See also QString::toUShort().

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

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.

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

### QByteArray QStringView::toUtf8() const

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.

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

### int QStringView::toWCharArray(wchar_t *array) const

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.

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.

`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

### uint qHash(QStringView key, uint seed = 0)

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

This function was introduced in Qt 5.10.