内容

• 公共函数
• 相关非成员
• 详细描述

QLatin1String 类

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

头：	#include <QLatin1String>
qmake:	QT += core

• 所有成员列表，包括继承成员

注意： 此类的所有函数 可重入 .

公共函数

	QLatin1String ()
	QLatin1String (const char * str )
	QLatin1String (const char * str , int size )
	QLatin1String (const QByteArray & str )
QLatin1Char	at (int pos ) const
const char *	data () const
const char *	latin1 () const
QLatin1String	left (int length ) const
QLatin1String	mid (int start ) const
QLatin1String	mid (int start , int length ) const
QLatin1String	right (int length ) const
int	size () 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
bool	operator>= (const QString & other ) const
bool	operator>= (const char * other ) const
bool	operator>= (const QByteArray & other ) const
QLatin1Char	operator[] (int pos ) const

相关非成员

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 )

详细描述

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

很多 QString 's member functions are overloaded to accept const char * 而不是 QString . This includes the copy constructor, the assignment operator, the comparison operators, and various other functions such as insert() , replace() ，和 indexOf() . These functions are usually optimized to avoid constructing a QString 对象为 const char * data. For example, assuming str 是 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 * 。使用 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);
					

注意： 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.

另请参阅 QString , QLatin1Char ，和 QStringLiteral .

成员函数文档编制

QLatin1String:: QLatin1String ()

构造 QLatin1String object that stores a nullptr.

该函数在 Qt 5.6 引入。

QLatin1String:: QLatin1String (const char * str )

构造 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.

另请参阅 latin1 ().

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

构造 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.

另请参阅 latin1 ().

QLatin1String:: QLatin1String (const QByteArray & str )

构造 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.

另请参阅 latin1 ().

QLatin1Char QLatin1String:: at ( int pos ) const

返回字符位于位置 pos 在此对象。

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

该函数在 Qt 5.8 引入。

另请参阅 operator[] ().

const char *QLatin1String:: data () const

Returns the Latin-1 string stored in this object.

const char *QLatin1String:: latin1 () const

Returns the Latin-1 string stored in this object.

QLatin1String QLatin1String:: left ( int length ) const

返回子字符串长度 length starting at position 0 in this object.

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

该函数在 Qt 5.8 引入。

另请参阅 mid () 和 right ().

QLatin1String QLatin1String:: mid ( int start ) const

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

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

该函数在 Qt 5.8 引入。

另请参阅 left () 和 right ().

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

这是重载函数。

返回子字符串长度 length 起始于位置 start 在此对象。

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

该函数在 Qt 5.8 引入。

另请参阅 left () 和 right ().

QLatin1String QLatin1String:: right ( int length ) const

返回子字符串长度 length 起始于位置 size () - length 在此对象。

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

该函数在 Qt 5.8 引入。

另请参阅 mid () 和 left ().

int QLatin1String:: size () const

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

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

返回 true if this string is not equal to string other ；否则返回 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

此函数重载 operator!= ().

The other const char pointer is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 4.3 引入。

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

此函数重载 operator!= ().

The other byte array is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 5.0 引入。

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

返回 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 () 函数。

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

这是重载函数。

The other const char pointer is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 4.3 引入。

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

这是重载函数。

The other const char pointer is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 5.0 引入。

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

返回 true if this string is lexically less than or equal to string other ；否则返回 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

这是重载函数。

The other const char pointer is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 4.3 引入。

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

这是重载函数。

The other array is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 5.0 引入。

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

返回 true if this string is equal to string other ；否则返回 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

这是重载函数。

The other const char pointer is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 4.3 引入。

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

这是重载函数。

The other byte array is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 5.0 引入。

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

返回 true if this string is lexically greater than string other ；否则返回 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

这是重载函数。

The other const char pointer is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 4.3 引入。

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

这是重载函数。

The other const char pointer is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 5.0 引入。

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

返回 true if this string is lexically greater than or equal to string other ；否则返回 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

这是重载函数。

The other const char pointer is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 4.3 引入。

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

这是重载函数。

The other array is converted to a QString 使用 QString::fromUtf8 () 函数。

可以禁用此运算符通过定义 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.

该函数在 Qt 5.0 引入。

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

返回字符位于位置 pos 在此对象。

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

该函数在 Qt 5.8 引入。

另请参阅 at ().

相关非成员

bool operator!= ( QLatin1String s1 , QLatin1String s2 )

返回 true 若字符串 s1 is lexically unequal to string s2 ；否则返回 false .

bool operator< ( QLatin1String s1 , QLatin1String s2 )

返回 true 若字符串 s1 is lexically smaller than string s2 ；否则返回 false .

bool operator<= ( QLatin1String s1 , QLatin1String s2 )

返回 true 若字符串 s1 is lexically smaller than or equal to string s2 ；否则返回 false .

bool operator== ( QLatin1String s1 , QLatin1String s2 )

返回 true 若字符串 s1 is lexically equal to string s2 ；否则返回 false .

bool operator> ( QLatin1String s1 , QLatin1String s2 )

返回 true 若字符串 s1 词法上大于字符串 s2 ；否则返回 false .

bool operator>= ( QLatin1String s1 , QLatin1String s2 )

返回 true 若字符串 s1 词法上大于等于字符串 s2 ；否则返回 false .