| Home | All Classes | Main Classes | Annotated | Grouped Classes | Functions | |
The QString class provides an abstraction of Unicode text and the classic C null-terminated char array. More...
#include <qstring.h>
The QString class provides an abstraction of Unicode text and the classic C null-terminated char array.
QString uses implicit sharing, which makes it very efficient and easy to use.
In all of the QString methods that take const char * parameters, the const char * is interpreted as a classic C-style 0-terminated ASCII string. It is legal for the const char * parameter to be 0. If the const char * is not 0-terminated, the results are undefined. Functions that copy classic C strings into a QString will not copy the terminating 0 character. The QChar array of the QString (as returned by unicode()) is generally not terminated by a null.
A QString that has not been assigned to anything is null, i.e. both the length and data pointer is 0. A QString that references the empty string ("", a single '\0' char) is empty. Both null and empty QStrings are legal parameters to the methods. Assigning (const char *) 0 to QString gives a null QString. For convenience, QString::null is a null QString. When sorting, empty strings come first, followed by non-empty strings, followed by null strings. We recommend using if ( !str.isNull() ) to check for a non-null string rather than if ( !str ); see operator!() for an explanation.
Note that if you find that you are mixing usage of QCString, QString, and QByteArray, this causes lots of unnecessary copying and might indicate that the true nature of the data you are dealing with is uncertain. If the data is 0-terminated 8-bit data, use QCString; if it is unterminated (i.e. contains 0s) 8-bit data, use QByteArray; if it is text, use QString.
Lists of strings are handled by the QStringList class. You can split a string into a list of strings using QStringList::split(), and join a list of strings into a single string with an optional separator using QStringList::join(). You can obtain a list of strings from a string list that contain a particular substring or that match a particular regex using QStringList::grep().
Note for C programmers
Due to C++'s type system and the fact that QString is implicitly shared, QStrings may be treated like ints or other simple base types. For example:
QString boolToString( bool b )
{
QString result;
if ( b )
result = "True";
else
result = "False";
return result;
}
The variable, result, is an auto variable allocated on the stack. When return is called, because we're returning by value, The copy constructor is called and a copy of the string is returned. (No actual copying takes place thanks to the implicit sharing, see below.)
Throughout Qt's source code you will encounter QString usages like this:
QString func( const QString& input )
{
QString output = input;
// process output
return output;
}
The 'copying' of input to output is almost as fast as copying a pointer because behind the scenes copying is achieved by incrementing a reference count. QString operates on a copy-on-write basis, only copying if an instance is actually changed.
If you wish to create a deep copy of a QString without loosing any Unicode information then you should use the QString constructor that takes a QChar*. For example:
QString a("abcd");
QString b( a.unicode(), b.length() );
Otherwise, using the QString constructor that takes a const char* will be sufficent. For example:
QString a("abcd");
QString b( a.latin1() );
See also QChar, QCString, QByteArray, QConstString, Implicitly and Explicitly Shared Classes, Text Related Classes and Non-GUI Classes.
Any of the last four values can be OR-ed together to form a flag.
See also section().
Constructs a null string. This is a string that has not been assigned to anything, i.e. both the length and data pointer is 0.
See also isNull().
If unicode and length are 0, then a null string is created.
If only unicode is 0, the string is empty but has length characters of space preallocated - QString expands automatically anyway, but this may speed up some cases a little. We recommend using the plain constructor and setLength() for this purpose since it will result in more readable code.
See also isNull() and setLength().
If str is 0, then a null string is created.
This is a cast constructor, but it is perfectly safe: converting a Latin1 const char* to QString preserves all the information. You can disable this constructor by defining QT_NO_CAST_ASCII when you compile your applications. You can also make QString objects by using setLatin1(), fromLatin1(), fromLocal8Bit(), and fromUtf8(). Or whatever encoding is appropriate for the 8-bit data you have.
See also isNull().
Destroys the string and frees the "real" string if this is the last copy of that string.
string = "Test";
string.append( "ing" ); // string == "Testing"
Equivalent to operator+=().
Example: dirview/dirview.cpp.
Appends character ch to the string and returns a reference to the result.
Equivalent to operator+=().
Appends character ch to the string and returns a reference to the result.
Equivalent to operator+=().
This function will return a string that replaces the lowest occurrence of %i (i being '1' or '2' or ... or '9') with a.
The fieldwidth value specifies the minimum amount of space that a is padded to. A positive value will produce right-aligned text, whereas a negative value will produce left-aligned text.
QString firstName( "Joe" );
QString lastName( "Bloggs" );
QString fullName;
fullName = QString( "First name is '%1', last name is '%2'" )
.arg( firstName )
.arg( lastName );
// fullName == First name is 'Joe', last name is 'Bloggs'
Warning: If you use arg() to construct "real" sentences like the one shown in the examples above, then this may cause problems with translation (when you use the tr() function).
If there is no %i pattern, a warning message (qWarning()) is outputted and the text is appended at the end of the string. This is error recovery done by the function and should not occur in correct code.
See also QObject::tr().
The fieldwidth value specifies the minimum amount of space that a is padded to. A positive value will produce a right-aligned number, whereas a negative value will produce a left-aligned number.
a is expressed in base base, which is 10 by default and must be between 2 and 36.
QString str;
str = QString( "Decimal 63 is %1 in hexadecimal" )
.arg( 63, 0, 16 );
// str == "Decimal 63 is 3f in hexadecimal"
a is expressed in base base, which is 10 by default and must be between 2 and 36.
a is expressed in base base, which is 10 by default and must be between 2 and 36.
a is expressed in base base, which is 10 by default and must be between 2 and 36.
a is expressed in base base, which is 10 by default and must be between 2 and 36.
a is expressed in base base, which is 10 by default and must be between 2 and 36.
a is assumed to be in the Latin1 character set.
Argument a is formatted according to the fmt format specified, which is g by default and can be any of the following:
In all cases the number of digits after the decimal point is equal to the precision specified in prec.
double d = 12.34;
QString ds = QString( "'E' format, precision 3, gives %1" )
.arg( d, 0, 'E', 3 );
// ds == "1.234E+001"
This function simply calls latin1() and returns the result.
Example: network/networkprotocol/nntp.cpp.
Returns the character at index i, or 0 if i is beyond the length of the string.
const QString string( "abcdefgh" );
QChar ch = string.at( 4 );
// ch == 'e'
If the QString is not const (i.e. const QString) or const& (i.e. const QString &), then the non-const overload of at() will be used instead.
The function returns a reference to the character at index i. The resulting reference can then be assigned to, or used immediately, but it will become invalid once further modifications are made to the original string.
If i is beyond the length of the string then the string is expanded with QChar::null.
Lexically compares s1 with s2 and returns an integer less than, equal to, or greater than zero if s1 is less than, equal to, or greater than s2.
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().
int a = QString::compare( "def", "abc" ); // a > 0
int b = QString::compare( "abc", "def" ); // b < 0
int c = QString::compare(" abc", "abc" ); // c == 0
Lexically compares this string with s and returns an integer less than, equal to, or greater than zero if it is less than, equal to, or greater than s.
Applies possible ligatures to a QString. Useful when composition-rich text requires rendering with glyph-poor fonts, but it also makes compositions such as QChar(0x0041) ('A') and QChar(0x0308) (Unicode accent diaresis), giving QChar(0x00c4) (German A Umlaut).
Returns the QChar at index i by value.
Equivalent to at(i).
See also ref().
If cs is TRUE then the match is case sensitive. If cs is FALSE, then the match is case insensitive.
QString string( "Trolltech and Qt" );
int i = string.contains( 't', FALSE ); // i == 3
Examples: fileiconview/qfileiconview.cpp and mdi/application.cpp.
Returns the number of times the string str occurs in the string.
If cs is TRUE then the match is case sensitive. If cs is FALSE, then the match is case insensitive.
Returns the number of times str occurs in the string.
The match is case sensitive if cs is TRUE or case insensitive if cs if FALSE.
This function counts overlapping strings, so in the example below, there are two instances of "ana" in "bananas".
QString str( "bananas" );
int i = str.contains( "ana" ); // i == 2
See also findRev().
Returns the number of times the regexp, rx, occurs in the string.
This function counts overlapping occurrences, so in the example below, there are four instances of "ana" or "ama".
QString str = "banana and panama";
QRegExp rxp = QRegExp( "a[nm]a", TRUE, FALSE );
int i = str.contains( rxp ); // i == 4
See also find() and findRev().
This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.
In Qt 2.0 and later, all calls to this function are needless. Just remove them.
This function is obsolete. It is provided to keep old source working. We strongly advise against using it in new code.
Returns a pointer to a 0-terminated classic C string.
In Qt 1.x, this returned a char* allowing direct manipulation of the string as a sequence of bytes. In Qt 2.x where QString is a Unicode string, char* conversion constructs a temporary string, and hence direct character operations are meaningless.
See also startsWith().
If len is negative (the default), the current string length is used.
QString str;
str.fill( 'g', 5 ); // string == "ggggg"
Returns the position of the first occurrence of rx or -1 if rx was not found.
QString string( "bananas" );
int i = string.find( QRegExp("an"), 0 ); // i == 1
See also findRev(), replace() and contains().
Example: network/mail/smtp.cpp.
Finds the first occurrence of the character c, starting at position index. If index is -1, the search starts at the last character; if -2, at the next to last character and so on. (See findRev() for searching backwards.)
If cs is TRUE, then the search is case sensitive. If cs is FALSE, then the search is case insensitive.
Returns the position of c or -1 if c could not be found.
Find character c starting from position index. If cs is TRUE then the match is case sensitive. If cs is FALSE, then the match is case insensitive.
Finds the first occurrence of the string str, starting at position index. If index is -1, the search starts at the last character, if it is -2, at the next to last character and so on. (See findRev() for searching backwards.)
The search is case sensitive if cs is TRUE or case insensitive if cs is FALSE.
Returns the position of str or -1 if str could not be found.
Equivalent to find(QString(str), index).
Equivalent to findRev(QString(str), index).
Finds the first occurrence of the character c, starting at position index and searching backwards. If the index is -1, the search starts at the last character, if it is -2, at the next to last character and so on.
Returns the position of c or -1 if c could not be found.
If cs is TRUE then the search is case sensitive. If cs is FALSE then the search is case insensitive.
QString string( "bananas" );
int i = string.findRev( 'a' ); // i == 5
Find character c starting from position index and working backwards. If cs is TRUE then the match is case sensitive. If cs is FALSE, then the match is case insensitive.
Finds the first occurrence of the string str, starting at position index and searching backwards. If the index is -1, the search starts at the last character, if it is -2, at the next to last character and so on.
Returns the position of str or -1 if str could not be found.
If cs is TRUE then the search is case sensitive. If cs is FALSE then the search is case insensitive.
QString string("bananas");
int i = string.findRev( "ana" ); // i == 3
Finds the first occurrence of the regexp rx, starting at position index and searching backwards. If the index is -1, the search starts at the last character, if it is -2, at the next to last character and so on. (See findRev() for searching backwards.)
Returns the position of rx or -1 if rx could not be found.
QString string( "bananas" );
int i = string.findRev( QRegExp("an") ); // i == 3
See also find().
This is the same as the QString(const char*) constructor, but you can make that constructor invisible if you compile with the define QT_NO_CAST_ASCII, in which case you can explicitly create a QString from Latin-1 text using this function.
QString str = QString::fromLatin1( "123456789", 5 );
// str == "12345"
Examples: listbox/listbox.cpp and network/mail/smtp.cpp.
QString str = QString::fromLocal8Bit( "123456789", 5 );
// str == "12345"
local8Bit is assumed to be encoded in a locale-specific format.
See QTextCodec for more diverse coding/decoding of Unicode strings.
QString str = QString::fromUtf8( "123456789", 5 );
// str == "12345"
See QTextCodec for more diverse coding/decoding of Unicode strings.
Example: fonts/simple-qfont-demo/viewer.cpp.
If index is beyond the end of the string, the string is extended with spaces to length index and s is then appended and returns a reference to the string.
QString string( "I like fish" );
str = string.insert( 2, "don't " );
// str == "I don't like fish"
See also remove() and replace().
Examples: themes/themes.cpp and xform/xform.cpp.
Inserts the character in s into the string before the position index len number of times and returns a reference to the string.
Insert c into the string at (before) position index and returns a reference to the string.
If index is beyond the end of the string, the string is extended with spaces (ASCII 32) to length index and c is then appended.
Insert character c at position index.
Returns TRUE if the string is empty, i.e., if length() == 0. Thus, null strings are empty strings.
QString a( "" );
a.isEmpty(); // TRUE
a.isNull(); // FALSE
QString b;
b.isEmpty(); // TRUE
b.isNull(); // TRUE
See also isNull() and length().
Examples: addressbook/mainwindow.cpp, application/application.cpp, hello/main.cpp, mdi/application.cpp, network/networkprotocol/nntp.cpp, qmag/qmag.cpp and qwerty/qwerty.cpp.
Returns TRUE if the string is null. A null string is always empty.
QString a; // a.unicode() == 0, a.length() == 0
a.isNull(); // TRUE, because a.unicode() == 0
a.isEmpty(); // TRUE
See also isEmpty() and length().
Examples: i18n/main.cpp and qdir/qdir.cpp.
This function is mainly useful for boot-strapping legacy code to use Unicode.
The result remains valid so long as one unmodified copy of the source string exists.
See also utf8() and local8Bit().
Examples: fileiconview/qfileiconview.cpp and network/networkprotocol/nntp.cpp.
The whole string is returned if len exceeds the length of the string.
QString s = "Pineapple";
QString t = s.left( 4 ); // t == "Pine"
See also right(), mid() and isEmpty().
Example: themes/themes.cpp.
If truncate is FALSE and the length of the string is more than width, then the returned string is a copy of the string.
If truncate is TRUE and the length of the string is more than width, then any characters in a copy of the string after length width are removed, and the copy is returned.
QString s( "apple" );
QString t = s.leftJustify( 8, '.' ); // t == "apple..."
See also rightJustify().
Returns the length of the string.
Null strings and empty strings have zero length.
See also isNull() and isEmpty().
Examples: fileiconview/qfileiconview.cpp, network/networkprotocol/nntp.cpp, rot13/rot13.cpp and themes/themes.cpp.
See QTextCodec for more diverse coding/decoding of Unicode strings.
See also QString::fromLocal8Bit(), latin1() and utf8().
Compares s1 with s2 and returns an integer less than, equal to, or greater than zero if s1 is less than, equal to, or greater than s2.
The comparison is performed in a locale- and also platform-dependent manner. Use this function to present sorted lists of strings to the user.
See also QString::compare() and QTextCodec::locale().
Compares this string with s.
QString string( "TROlltECH" );
str = string.lower(); // str == "trolltech"
See also upper().
Example: scribble/scribble.cpp.
Returns a null string if the string is empty or index is out of range. Returns the whole string from index if index+len exceeds the length of the string.
QString s( "Five pineapples" );
QString t = s.mid( 5, 4 ); // t == "pine"
Examples: network/mail/smtp.cpp, qmag/qmag.cpp and themes/themes.cpp.
long a = 63;
QString str = QString::number( a, 16 ); // str == "3f"
QString str = QString::number( a, 16 ).upper(); // str == "3F"
See also setNum().
Examples: action/application.cpp, application/application.cpp, fonts/simple-qfont-demo/viewer.cpp, helpviewer/helpwindow.cpp, mdi/application.cpp and sql/overview/extract/main.cpp.
See also setNum().
See also setNum().
A convenience factory function that returns a string representation of the number n to the base base, which is 10 by default and must be between 2 and 36.
See also setNum().
Argument n is formatted according to the f format specified, which is g by default, and can be any of the following:
In all cases the number of digits after the decimal point is equal to the precision specified in prec.
double d = 12.34;
QString ds = QString( "'E' format, precision 3, gives %1" )
.arg( d, 0, 'E', 3 );
// ds == "1.234E+001"
See also setNum().
Returns latin1(). Be sure to see the warnings documented there. Note that for new code which you wish to be strictly Unicode-clean, you can define the macro QT_NO_ASCII_CAST when compiling your code to hide this function so that automatic casts are not done. This has the added advantage that you catch the programming error described under operator!().
QString name = getName();
if ( !name )
name = "Rodney";
Note that if you say
QString name = getName();
if ( name )
doSomethingWith(name);
It will call "operator const char*()", which is inefficent; you may wish to define the macro QT_NO_ASCII_CAST when writing code which you wish to remain Unicode-clean.
When you want the above semantics, use:
QString name = getName();
if ( !name.isNull() )
doSomethingWith(name);
Appends c to the string and returns a reference to the string.
Appends c to the string and returns a reference to the string.
Assigns a shallow copy of s to this string and returns a reference to this string. This is very fast because the string isn't actually copied.
Assigns a deep copy of str, interpreted as a classic C string to this string and returns a reference to this string.
If str is 0, then a null string is created.
See also isNull().
Assigns a deep copy of cs, interpreted as a classic C string, to this string and returns a reference to this string.
Sets the string to contain just the single character c.
Returns the character at index i, or QChar::null if i is beyond the length of the string.
If the QString is not const (i.e., const QString) or const& (i.e., const QString&), then the non-const overload of operator[] will be used instead.
The function returns a reference to the character at index i. The resulting reference can then be assigned to, or used immediately, but it will become invalid once further modifications are made to the original string.
If i is beyond the length of the string then the string is expanded with QChar::nulls, so that the QCharRef references a valid (null) character in the string.
The QCharRef internal class can be used much like a constant QChar, but if you assign to it, you change the original string (which will detach itself because of QString's copy-on-write semantics). You will get compilation errors if you try to use the result as anything but a QChar.
Inserts s at the beginning of the string and returns a reference to the string.
Equivalent to insert(0, s).
QString string = "42";
string.prepend( "The answer is " );
// string == "The answer is 42"
See also insert().
Inserts ch at the beginning of the string and returns a reference to the string.
Equivalent to insert(0, ch).
See also insert().
Inserts ch at the beginning of the string and returns a reference to the string.
Equivalent to insert(0, ch).
See also insert().
Returns the QChar at index i by reference, expanding the string with QChar::null if necessary. The resulting reference can be assigned to, or otherwise used immediately, but becomes invalid once furher modifications are made to the string.
QString string("ABCDEF");
QChar ch = string.ref( 3 ); // ch == 'D'
See also constref().
If index is beyond the length of the string, nothing happens. If index is within the string, but index plus len is beyond the end of the string, the string is truncated at position index.
QString string( "Montreal" );
string.remove( 1, 4 ); // string == "Meal"
See also insert() and replace().
If index is beyond the length of the string, nothing is deleted and s is appended at the end of the string. If index is valid, but index plus len is beyond the end of the string, the string is truncated at position index, then s is appended at the end.
QString string( "Say yes!" );
string = string.replace( 4, 3, "NO" );
// string == "Say NO!"
See also insert() and remove().
Examples: listviews/listviews.cpp, network/networkprotocol/nntp.cpp and qmag/qmag.cpp.
Replaces len characters starting at position index by slen characters of QChar data from s, and returns a reference to the string.
See also insert() and remove().
Replaces every occurrence of the regexp rx in the string with str. Returns a reference to the string.
QString string = "banana";
string = string.replace( QRegExp("an"), "" ); // string == "ba"
See also find() and findRev().
If len is greater than the length of the string then the whole string is returned.
QString string( "Pineapple" );
QString t = string.right( 5 ); // t == "apple"
See also left(), mid() and isEmpty().
Example: fileiconview/qfileiconview.cpp.
If truncate is FALSE and the length of the string is more than width, then the returned string is a copy of the string.
If truncate is TRUE and the length of the string is more than width, then the resulting string is truncated at position width.
QString string( "apple" );
QString t = string.rightJustify( 8, '.' ); // t == "...apple"
See also leftJustify().
This function returns a section of the string.
This string is treated as a sequence of fields separated by the character, sep. The returned string consists of the fields from position start to position end inclusive. If end is not specified, all fields from position start to the end of the string are included.
The flags argument can be used to affect some aspects of the function's behaviour, e.g. whether to be case sensitive, whether to skip empty fields and how to deal with leading and trailing separators; see SectionFlags.
QString csv( "forename,middlename,surname,phone" );
QString s = csv.section( ',', 2, 2 ); // s == "surname"
QString path( "/usr/local/bin/myapp" ); // First field is empty
QString s = path.section( '/', 3, 4 ); // s == "bin/myapp"
QString s = path.section( '/', 3, 3, SectionSkipEmpty ); // s == "myapp"
If start or end is negative, we count fields from the right of the string, the right-most field being -1, the one from right-most field being -2, and so on.
QString csv( "forename,middlename,surname,phone" );
QString s = csv.section( ',', -3, -2 ); // s == "middlename,surname"
QString path( "/usr/local/bin/myapp" ); // First field is empty
QString s = path.section( '/', -1 ); // s == "myapp"
See also QStringList::split().
This function returns a section of the string.
This string is treated as a sequence of fields separated by the string, sep. The returned string consists of the fields from position start to position end inclusive. If end is not specified, all fields from position start to the end of the string are included.
The flags argument can be used to affect some aspects of the function's behaviour, e.g. whether to be case sensitive, whether to skip empty fields and how to deal with leading and trailing separators; see SectionFlags.
QString data( "forename**middlename**surname**phone" );
QString s = data.section( "**", 2, 2 ); // s == "surname"
If start or end is negative, we count fields from the right of the string, the right-most field being -1, the one from right-most field being -2, and so on.
QString data( "forename**middlename**surname**phone" );
QString s = data.section( "**", -3, -2 ); // s == "middlename**surname"
See also QStringList::split().
This function returns a section of the string.
This string is treated as a sequence of fields separated by the regular expression, reg. The returned string consists of the fields from position start to position end inclusive. If end is not specified, all fields from position start to the end of the string are included.
The flags argument can be used to affect some aspects of the function's behaviour, e.g. whether to be case sensitive, whether to skip empty fields and how to deal with leading and trailing separators; see SectionFlags.
QString line( "forename\tmiddlename surname \t \t phone" );
QRegExp sep( "\s+" );
QString s = line.section( sep, 2, 2 ); // s == "surname"
If start or end is negative, we count fields from the right of the string, the right-most field being -1, the one from right-most field being -2, and so on.
QString line( "forename\tmiddlename surname \t \t phone" );
QRegExp sep( "\\s+" );
QString s = line.section( sep, -3, -2 ); // s == "middlename surname"
Warning: Section on QRegExp is much more expensive than the overloaded string and character versions.
See also QStringList::split() and simplifyWhiteSpace().
Sets the character at position index to c and expands the string if necessary, filling with spaces.
This method is redundant in Qt 3.x, because operator[] will expand the string as necessary.
If str is 0 a null string is created. If str is "", an empty string is created.
See also isNull() and isEmpty().
If newLen is 0, then the string becomes empty, unless the string is null, in which case it remains null.
This function always detaches the string from other references to the same data.
This function is useful for code that needs to build up a long string and wants to avoid repeated reallocation. In this example, we want to add to the string until some condition is true, and we're fairly sure that size is big enough:
QString result;
int resultLength = 0;
result.setLength( newLen ) // allocate some space
while ( ... ) {
result[resultLength++] = ... // fill (part of) the space with data
}
result.truncate[resultLength]; // and get rid of the undefined junk
If newLen is an underestimate, the worst that will happen is that the loop will slow down.
See also truncate(), isNull(), isEmpty() and length().
The base is 10 by default and must be between 2 and 36.
QString string;
string = string.setNum( 1234 ); // string == "1234"
Sets the string to the printed value of n in base base and returns a reference to the string.
The base is 10 by default and must be between 2 and 36.
Sets the string to the printed value of n in base base and returns a reference to the string.
The base is 10 by default and must be between 2 and 36.
Sets the string to the printed value of n in base base and returns a reference to the string.
The base is 10 by default and must be between 2 and 36.
Sets the string to the printed value of n in base base and returns a reference to the string.
The base is 10 by default and must be between 2 and 36.
Sets the string to the printed value of n in base base and returns a reference to the string.
The base is 10 by default and must be between 2 and 36.
Sets the string to the printed value of n, formatted in format f with precision prec, and returns a reference to the string.
The format f can be 'f', 'F', 'e', 'E', 'g' or 'G'. See arg() for an explanation of the formats.
Sets the string to the printed value of n, formatted in format f with precision prec, and returns a reference to the string.
The format f can be 'f', 'F', 'e', 'E', 'g' or 'G'. See arg() for an explanation of the formats.
See also setLatin1() and isNull().
If unicode_as_ushorts is null, nothing is copied, but the string is still resized to len. If len is zero, the string becomes a null string.
See also setLatin1() and isNull().
Whitespace means any character for which QChar::isSpace() returns TRUE. This includes UNICODE characters with decimal values 9 (TAB), 10 (LF), 11 (VT), 12 (FF), 13 (CR), and 32 (Space).
QString string = " lots\t of\nwhite space ";
QString t = string.simplifyWhiteSpace();
// t == "lots of white space"
See also stripWhiteSpace().
The %s escape sequence expects a utf8() encoded string. The format string cformat is expected to be in latin1. If you need a unicode format string, use arg() instead. For typesafe string building, with full Unicode support, you can use QTextOStream like this:
QString str;
QString s = ...;
int x = ...;
QTextOStream( &str ) << s << " : " << x;
For translations, especially if the strings contains more than one escape sequence, you should consider using the arg() function instead. This allows the order of the replacements to be controlled by the translator, and has Unicode support.
See also arg().
Examples: dclock/dclock.cpp, forever/forever.cpp, layout/layout.cpp, qmag/qmag.cpp, scrollview/scrollview.cpp, tooltip/tooltip.cpp and xform/xform.cpp.
QString string("Bananas");
bool a = string.startsWith("Ban"); // a == TRUE
See also endsWith().
Whitespace means any character for which QChar::isSpace() returns TRUE. This includes UNICODE characters with decimal values 9 (TAB), 10 (LF), 11 (VT), 12 (FF), 13 (CR) and 32 (Space), and may also include other Unicode characters.
QString string = " white space ";
QString s = string.stripWhiteSpace(); // s == "white space"
See also simplifyWhiteSpace().
If a conversion error occurs, *ok is set to FALSE (unless ok is null, the default) and 0 is returned. Otherwise, *ok is set to true.
QString string( "1234.56" );
double a = string.toDouble(); // a == 1234.56
See also number().
If a conversion error occurs, *ok is set to FALSE (unless ok is null, the default) and 0 is returned. Otherwise, *ok is set to true.
See also number().
If *ok is nonnull, and is TRUE then there have been no errors in the conversion. If *ok is nonnull, and is FALSE, then the string is not a number at all or it has invalid characters at the end.
QString str( "FF" );
bool ok;
int hex = str.toInt( &ok, 16 ); // hex == 255, ok == TRUE
int dec = str.toInt( &ok, 10 ); // dec == 0, ok == FALSE
See also number().
If a conversion error occurs, *ok is set to FALSE (unless ok is null, the default) and 0 is returned. Otherwise, *ok is set to true.
See also number().
If a conversion error occurs, *ok is set to FALSE (unless ok is null, the default) and 0 is returned. Otherwise, *ok is set to true.
If a conversion error occurs, *ok is set to FALSE (unless ok is null, the default) and 0 is returned. Otherwise, *ok is set to true.
See also number().
If a conversion error occurs, *ok is set to FALSE (unless ok is null, the default) and 0 is returned. Otherwise, *ok is set to true.
See also number().
If a conversion error occurs, *ok is set to FALSE (unless ok is null, the default) and 0 is returned. Otherwise, *ok is set to true.
QString s = "truncate me";
s.truncate( 5 ); // s == "trunc"
See also setLength().
Example: network/mail/smtp.cpp.
Returns the Unicode representation of the string. The result remains valid until the string is modified.
QString string( "TeXt" );
str = string.upper(); // t == "TEXT"
See also lower().
Examples: scribble/scribble.cpp and sql/overview/custom1/main.cpp.
See QTextCodec for more diverse coding/decoding of Unicode strings.
See also QString::fromUtf8(), local8Bit() and latin1().
Equivalent to compare(s1, s2) != 0.
Returns TRUE if s1 is not equal to s2 or FALSE if they are equal. Note that a null string is not equal to an empty string which is nonnull.
Equivalent to compare(s1, s2) != 0.
Returns TRUE if s1 is not equal to s2 or FALSE if they are equal. Note that a null string is not equal to an empty string which is nonnull.
Equivalent to compare(s1, s2) != 0.
Equivalent to s1.append(s2).
Returns a string which is the result of concatenating the string s1 and character s2.
Equivalent to s1.append(s2).
Returns a string which is the result of concatenating the character s1 and string s2.
Returns a string which is the result of concatenating the string s and character c.
Equivalent to s.append(c).
Returns a string which is the result of concatenating the character c and string s.
Equivalent to s.prepend(c).
Equivalent to compare(s1, s2) < 0.
Returns TRUE if s1 is lexically less than s2 or FALSE if it is not. The comparison is case sensitive. Note that a null string is not equal to an empty string which is nonnull.
Equivalent to compare(s1, s2) < 0.
See also Format of the QDataStream operators
Equivalent to compare(s1,s2) <= 0.
Returns TRUE if s1 is lexically less than or equal to s2 or FALSE if it is not. The comparison is case sensitive. Note that a null string is not equal to an empty string which is nonnull.
Equivalent to compare(s1, s2) <= 0.
Equivalent to compare(s1, s2) != 0.
Returns TRUE if s1 is equal to s2 or FALSE if they are different. Note that a null string is not equal to an empty string which is nonnull.
Equivalent to compare(s1, s2) == 0.
Returns TRUE if s1 is equal to s2 or FALSE if they are different. Note that a null string is not equal to an empty string which is nonnull.
Equivalent to compare(s1, s2) == 0.
Equivalent to compare(s1, s2) > 0.
Returns TRUE if s1 is lexically greater than s2 or FALSE if it is not. The comparison is case sensitive. Note that a null string is not equal to an empty string which is nonnull.
Equivalent to compare(s1, s2) > 0.
Equivalent to compare(s1, s2) >= 0.
Returns TRUE if s1 is lexically greater than or equal to s2 or FALSE if it is not. The comparison is case sensitive. Note that a null string is not equal to an empty string which is nonnull.
Equivalent to compare(s1, s2) >= 0.
See also Format of the QDataStream operators
This file is part of the Qt toolkit. Copyright © 1995-2002 Trolltech. All Rights Reserved.
| Copyright © 2002 Trolltech | Trademarks | Qt version 3.0.4
|