Qt 5.11 | Qt Core | C++ Classes | QLatin1String

Qt 5.11.3 Reference Documentation

# QLatin1String Class

The QLatin1String class provides a thin wrapper around an US-ASCII/Latin-1 encoded string literal. More...

Header: | #include <QLatin1String>
qmake: | QT += core

- List of all members, including inherited members

Note: All functions in this class are reentrant.

## Public Types

typedef | const_iterator
typedef | const_reference
typedef | difference_type
typedef | iterator
typedef | reference
typedef | size_type
typedef | value_type

## Public Functions

| QLatin1String()
| QLatin1String(const char *str)
| QLatin1String(const char *first, const char *last)
| QLatin1String(const char *str, int size)
| QLatin1String(const QByteArray &str)
QLatin1Char | at(int pos) const
QLatin1Char | back() const
QLatin1String::const_iterator | begin() const
QLatin1String::const_iterator | cbegin() const
QLatin1String::const_iterator | cend() const
void | chop(int length)
QLatin1String | chopped(int length) const
int | crbegin() const
int | crend() const
const char * | data() const
QLatin1String::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
QLatin1Char | front() const
bool | isEmpty() const
bool | isNull() const
const char * | latin1() const
QLatin1String | left(int length) const
QLatin1String | mid(int start) const
QLatin1String | mid(int start, int length) const
int | rbegin() const
int | rend() const
QLatin1String | right(int length) const
int | 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
QLatin1String | trimmed() const
void | truncate(int length)
bool | operator!=(const QString &other) const
bool | operator!=(const char *other) const
bool | operator!=(const QByteArray &other) const
bool | operator<(const QString &other) const
bool | operator<(const char *other) const
bool | operator<(const QByteArray &other) const
bool | operator<=(const QString &other) const
bool | operator<=(const char *other) const
bool | operator<=(const QByteArray &other) const
bool | operator==(const QString &other) const
bool | operator==(const char *other) const
bool | operator==(const QByteArray &other) const
bool | operator>(const QString &other) const
bool | operator>(const char *other) const
bool | operator>(const QByteArray &other) const
bool | operator>=(const QString &other) const
bool | operator>=(const char *other) const
bool | operator>=(const QByteArray &other) const
QLatin1Char | operator[](int pos) const

## Related Non-Members

bool | operator!=(QLatin1String s1, QLatin1String s2)
bool | operator<(QLatin1String s1, QLatin1String s2)
bool | operator<=(QLatin1String s1, QLatin1String s2)
bool | operator==(QLatin1String s1, QLatin1String s2)
bool | operator>(QLatin1String s1, QLatin1String s2)
bool | operator>=(QLatin1String s1, QLatin1String s2)

## Detailed Description

The QLatin1String class provides a thin wrapper around an US-ASCII/Latin-1 encoded string literal.

Many of QString's member functions are overloaded to accept `const char *` instead of QString. This includes the copy constructor, the assignment operator, the comparison operators, and various other functions such as insert(), replace(), and indexOf(). These functions are usually optimized to avoid constructing a QString object for the `const char *` data. For example, assuming `str` is a QString,

      if (str == "auto" || str == "extern"
              || str == "static" || str == "register") {
          ...
      }

is much faster than

      if (str == QString("auto") || str == QString("extern")
              || str == QString("static") || str == QString("register")) {
          ...
      }

because it doesn't construct four temporary QString objects and make a deep copy of the character data.

Applications that define `QT_NO_CAST_FROM_ASCII` (as explained in the QString documentation) don't have access to QString's `const char *` API. To provide an efficient way of specifying constant Latin-1 strings, Qt provides the QLatin1String, which is just a very thin wrapper around a `const char *`. Using QLatin1String, the example code above becomes

      if (str == QLatin1String("auto")
              || str == QLatin1String("extern")
              || str == QLatin1String("static")
              || str == QLatin1String("register") {
          ...
      }

This is a bit longer to type, but it provides exactly the same benefits as the first version of the code, and is faster than converting the Latin-1 strings using QString::fromLatin1().

Thanks to the QString(QLatin1String) constructor, QLatin1String can be used everywhere a QString is expected. For example:

      QLabel *label = new QLabel(QLatin1String("MOD"), this);

Note: If the function you're calling with a QLatin1String argument isn't actually overloaded to take QLatin1String, the implicit conversion to QString will trigger a memory allocation, which is usually what you want to avoid by using QLatin1String in the first place. In those cases, using QStringLiteral may be the better option.

See also QString, QLatin1Char, and QStringLiteral.

## Member Type Documentation

### typedef QLatin1String::const_iterator

This typedef provides an STL-style const iterator for QLatin1String.

This typedef was introduced in Qt 5.10.

See also iterator and const_reverse_iterator.

### typedef QLatin1String::const_reference

Alias for `reference`. Provided for compatibility with the STL.

This typedef was introduced in Qt 5.11.

### typedef QLatin1String::difference_type

Alias for `int`. Provided for compatibility with the STL.

This typedef was introduced in Qt 5.10.

### typedef QLatin1String::iterator

This typedef provides an STL-style const iterator for QLatin1String.

QLatin1String does not support mutable iterators, so this is the same as const_iterator.

This typedef was introduced in Qt 5.10.

See also const_iterator and reverse_iterator.

### typedef QLatin1String::reference

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

This typedef was introduced in Qt 5.10.

### typedef QLatin1String::size_type

Alias for `int`. Provided for compatibility with the STL.

This typedef was introduced in Qt 5.10.

### typedef QLatin1String::value_type

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

This typedef was introduced in Qt 5.10.

## Member Function Documentation

### bool QLatin1String::endsWith(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

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

### bool QLatin1String::endsWith(QChar ch) const

### bool QLatin1String::endsWith(QChar ch, Qt::CaseSensitivity cs) const

Returns `true` if this Latin-1 string 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.

This documentation was introduced in Qt 5.10.

See also startsWith().

### bool QLatin1String::startsWith(QStringView str, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

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

### bool QLatin1String::startsWith(QChar ch) const

### bool QLatin1String::startsWith(QChar ch, Qt::CaseSensitivity cs) const

Returns `true` if this Latin-1 string 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.

This documentation was introduced in Qt 5.10.

See also endsWith().

### QLatin1String::QLatin1String()

Constructs a QLatin1String object that stores a nullptr.

This function was introduced in Qt 5.6.

### QLatin1String::QLatin1String(const char *str)

Constructs a QLatin1String object that stores str.

The string data is not copied. The caller must be able to guarantee that str will not be deleted or modified as long as the QLatin1String object exists.

See also latin1().

### QLatin1String::QLatin1String(const char *first, const char *last)

Constructs a QLatin1String object that stores first with length (last - first).

The range `[first,last)` must remain valid for the lifetime of this Latin-1 string object.

Passing `nullptr` as first is safe if last is `nullptr`, too, and results in a null Latin-1 string.

The behavior is undefined if last precedes first, first is `nullptr` and last is not, or if `last - first > INT_MAX`.

This function was introduced in Qt 5.10.

### QLatin1String::QLatin1String(const char *str, int size)

Constructs a QLatin1String object that stores str with size.

The string data is not copied. The caller must be able to guarantee that str will not be deleted or modified as long as the QLatin1String object exists.

See also latin1().

### QLatin1String::QLatin1String(const QByteArray &str)

Constructs a QLatin1String object that stores str.

The string data is not copied. The caller must be able to guarantee that str will not be deleted or modified as long as the QLatin1String object exists.

See also latin1().

### QLatin1Char QLatin1String::at(int pos) const

Returns the character at position pos in this object.

Note: This function performs no error checking. The behavior is undefined when pos < 0 or pos >= size().

This function was introduced in Qt 5.8.

See also operator[]().

### QLatin1Char QLatin1String::back() const

Returns the last character in the string. Same as `at(size() - 1)`.

This function is provided for STL compatibility.

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

This function was introduced in Qt 5.10.

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

### QLatin1String::const_iterator QLatin1String::begin() const

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

This function is provided for STL compatibility.

This function was introduced in Qt 5.10.

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

### QLatin1String::const_iterator QLatin1String::cbegin() const

Same as begin().

This function is provided for STL compatibility.

This function was introduced in Qt 5.10.

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

### QLatin1String::const_iterator QLatin1String::cend() const

Same as end().

This function is provided for STL compatibility.

This function was introduced in Qt 5.10.

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

### void QLatin1String::chop(int length)

Truncates this string by length characters.

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

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

This function was introduced in Qt 5.10.

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

### QLatin1String QLatin1String::chopped(int 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().

This function was introduced in Qt 5.10.

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

### int QLatin1String::crbegin() const

Same as rbegin().

This function is provided for STL compatibility.

This function was introduced in Qt 5.10.

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

### int QLatin1String::crend() const

Same as rend().

This function is provided for STL compatibility.

This function was introduced in Qt 5.10.

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

### const char *QLatin1String::data() const

Returns the Latin-1 string stored in this object.

### QLatin1String::const_iterator QLatin1String::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.

This function was introduced in Qt 5.10.

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

### QLatin1Char QLatin1String::front() const

Returns the first character in the string. Same as `at(0)`.

This function is provided for STL compatibility.

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

This function was introduced in Qt 5.10.

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

### bool QLatin1String::isEmpty() const

Returns whether the Latin-1 string stored in this object is empty (`size() == 0`) or not.

This function was introduced in Qt 5.10.

See also isNull() and size().

### bool QLatin1String::isNull() const

Returns whether the Latin-1 string stored in this object is null (`data() == nullptr`) or not.

This function was introduced in Qt 5.10.

See also isEmpty() and data().

### const char *QLatin1String::latin1() const

Returns the Latin-1 string stored in this object.

### QLatin1String QLatin1String::left(int length) const

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

Note: This function performs no error checking. The behavior is undefined when length < 0 or length > size().

This function was introduced in Qt 5.8.

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

### QLatin1String QLatin1String::mid(int start) const

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

Note: This function performs no error checking. The behavior is undefined when start < 0 or start > size().

This function was introduced in Qt 5.8.

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

### QLatin1String QLatin1String::mid(int start, int length) const

This is an overloaded function.

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

Note: This function performs no error checking. The behavior is undefined when start < 0, length < 0, or start + length > size().

This function was introduced in Qt 5.8.

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

### int QLatin1String::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.

This function was introduced in Qt 5.10.

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

### int QLatin1String::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.

This function was introduced in Qt 5.10.

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

### QLatin1String QLatin1String::right(int length) const

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

Note: This function performs no error checking. The behavior is undefined when length < 0 or length > size().

This function was introduced in Qt 5.8.

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

### int QLatin1String::size() const

Returns the size of the Latin-1 string stored in this object.

### QLatin1String QLatin1String::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 ' '.

This function was introduced in Qt 5.10.

### void QLatin1String::truncate(int length)

Truncates this string to length length.

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

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

This function was introduced in Qt 5.10.

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

### bool QLatin1String::operator!=(const QString &other) const

Returns `true` if this string is not equal to string other; otherwise returns `false`.

The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with QString::localeAwareCompare().

### bool QLatin1String::operator!=(const char *other) const

This function overloads operator!=().

The other const char pointer is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 4.3.

### bool QLatin1String::operator!=(const QByteArray &other) const

This function overloads operator!=().

The other byte array is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 5.0.

### bool QLatin1String::operator<(const QString &other) const

Returns `true` if this string is lexically less than the other string; otherwise returns `false`.

The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings using the QString::localeAwareCompare() function.

### bool QLatin1String::operator<(const char *other) const

This is an overloaded function.

The other const char pointer is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 4.3.

### bool QLatin1String::operator<(const QByteArray &other) const

This is an overloaded function.

The other const char pointer is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 5.0.

### bool QLatin1String::operator<=(const QString &other) const

Returns `true` if this string is lexically less than or equal to string other; otherwise returns `false`.

The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with QString::localeAwareCompare().

### bool QLatin1String::operator<=(const char *other) const

This is an overloaded function.

The other const char pointer is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 4.3.

### bool QLatin1String::operator<=(const QByteArray &other) const

This is an overloaded function.

The other array is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 5.0.

### bool QLatin1String::operator==(const QString &other) const

Returns `true` if this string is equal to string other; otherwise returns `false`.

The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with QString::localeAwareCompare().

### bool QLatin1String::operator==(const char *other) const

This is an overloaded function.

The other const char pointer is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 4.3.

### bool QLatin1String::operator==(const QByteArray &other) const

This is an overloaded function.

The other byte array is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 5.0.

### bool QLatin1String::operator>(const QString &other) const

Returns `true` if this string is lexically greater than string other; otherwise returns `false`.

The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with QString::localeAwareCompare().

### bool QLatin1String::operator>(const char *other) const

This is an overloaded function.

The other const char pointer is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 4.3.

### bool QLatin1String::operator>(const QByteArray &other) const

This is an overloaded function.

The other const char pointer is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 5.0.

### bool QLatin1String::operator>=(const QString &other) const

Returns `true` if this string is lexically greater than or equal to string other; otherwise returns `false`.

The comparison is based exclusively on the numeric Unicode values of the characters and is very fast, but is not what a human would expect. Consider sorting user-interface strings with QString::localeAwareCompare().

### bool QLatin1String::operator>=(const char *other) const

This is an overloaded function.

The other const char pointer is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 4.3.

### bool QLatin1String::operator>=(const QByteArray &other) const

This is an overloaded function.

The other array is converted to a QString using the QString::fromUtf8() function.

You can disable this operator by defining `QT_NO_CAST_FROM_ASCII` when you compile your applications. This can be useful if you want to ensure that all user-visible strings go through QObject::tr(), for example.

This function was introduced in Qt 5.0.

### QLatin1Char QLatin1String::operator[](int pos) const

Returns the character at position pos in this object.

Note: This function performs no error checking. The behavior is undefined when pos < 0 or pos >= size().

This function was introduced in Qt 5.8.

See also at().

## Related Non-Members

### bool operator!=(QLatin1String s1, QLatin1String s2)

Returns `true` if string s1 is lexically unequal to string s2; otherwise returns `false`.

### bool operator<(QLatin1String s1, QLatin1String s2)

Returns `true` if string s1 is lexically smaller than string s2; otherwise returns `false`.

### bool operator<=(QLatin1String s1, QLatin1String s2)

Returns `true` if string s1 is lexically smaller than or equal to string s2; otherwise returns `false`.

### bool operator==(QLatin1String s1, QLatin1String s2)

Returns `true` if string s1 is lexically equal to string s2; otherwise returns `false`.

### bool operator>(QLatin1String s1, QLatin1String s2)

Returns `true` if string s1 is lexically greater than string s2; otherwise returns `false`.

### bool operator>=(QLatin1String s1, QLatin1String s2)

Returns `true` if string s1 is lexically greater than or equal to string s2; otherwise returns `false`.