QString Class Reference |
Note for C ProgrammersDue to C++'s type system and the fact that QString is implicitly shared, QStrings may be treated like ints or other basic types. For example: QString Widget.boolToString(bool b) { QString result; if (b) result = "True"; else result = "False"; return result; } The result variable, is a normal variable allocated on the stack. When return is called, and 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. |
For historical reasons, QString distinguishes between a null string and an empty string. A null string is a string that is initialized using QString's default constructor or by passing (const char *)0 to the constructor. An empty string is any string with size 0. A null string is always empty, but an empty string isn't necessarily null:
QString().isNull(); // returns true QString().isEmpty(); // returns true QString("").isNull(); // returns false QString("").isEmpty(); // returns true QString("abc").isNull(); // returns false QString("abc").isEmpty(); // returns false
All functions except isNull() treat null strings the same as empty strings. For example, toAscii().constData() returns a pointer to a '\0' character for a null string (not a null pointer), and QString() compares equal to QString(""). We recommend that you always use the isEmpty() function and avoid isNull().
See also fromRawData(), QChar, QLatin1String, QByteArray, and QStringRef.
This enum describes the various normalized forms of Unicode text.
Constant | Value | Description |
---|---|---|
QString.NormalizationForm_D | 0 | Canonical Decomposition |
QString.NormalizationForm_C | 1 | Canonical Decomposition followed by Canonical Composition |
QString.NormalizationForm_KD | 2 | Compatibility Decomposition |
QString.NormalizationForm_KC | 3 | Compatibility Decomposition followed by Canonical Composition |
See also normalized() and Unicode Standard Annex #15.
This enum specifies flags that can be used to affect various aspects of the section() function's behavior with respect to separators and empty fields.
Constant | Value | Description |
---|---|---|
QString.SectionDefault | 0x00 | Empty fields are counted, leading and trailing separators are not included, and the separator is compared case sensitively. |
QString.SectionSkipEmpty | 0x01 | Treat empty fields as if they don't exist, i.e. they are not considered as far as start and end are concerned. |
QString.SectionIncludeLeadingSep | 0x02 | Include the leading separator (if any) in the result string. |
QString.SectionIncludeTrailingSep | 0x04 | Include the trailing separator (if any) in the result string. |
QString.SectionCaseInsensitiveSeps | 0x08 | Compare the separator case-insensitively. |
The SectionFlags type is a typedef for QFlags<SectionFlag>. It stores an OR combination of SectionFlag values.
See also section().
This enum specifies how the split() function should behave with respect to empty strings.
Constant | Value | Description |
---|---|---|
QString.KeepEmptyParts | 0 | If a field is empty, keep it in the result. |
QString.SkipEmptyParts | 1 | If a field is empty, don't include it in the result. |
See also split().
Constructs a null string. Null strings are also empty.
See also isEmpty().
This method is only available if the QtGui module is imported.
Constructs a null string. Null strings are also empty.
See also isEmpty().
This method is only available if the QtScript module is imported.
Constructs a null string. Null strings are also empty.
See also isEmpty().
Constructs a string initialized with the first size characters of the QChar array unicode.
QString makes a deep copy of the string data.
Constructs a string of size 1 containing the character ch.
Constructs a string of the given size with every character set to ch.
See also fill().
Constructs a copy of the Latin-1 string str.
See also fromLatin1().
Constructs a copy of other.
This operation takes constant time, because QString is implicitly shared. This makes returning a QString from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes linear time.
See also operator=().
Appends the string str onto the end of this string.
Example:
QString x = "free";
QString y = "dom";
x.append(y);
// x == "freedom"
This is the same as using the insert() function:
x.insert(x.size(), y);
The append() function is typically very fast (constant time), because QString preallocates extra space at the end of the string data so it can grow without reallocating the entire string each time.
See also operator+=(), prepend(), and insert().
This is an overloaded member function, provided for convenience.
Appends the given string reference to this string and returns the result.
This function was introduced in Qt 4.4.
This is an overloaded member function, provided for convenience.
Appends the Latin-1 string str to this string.
This function returns a copy of this string where a replaces the lowest numbered occurrence of %1, %2, ..., %99.
The fieldWidth value specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value will produce right-aligned text, whereas a negative value will produce left-aligned text.
The following example shows how we could create a 'status' string when processing a list of files:
QString i; // current file's number QString total; // number of files to process QString fileName; // current file's name QString status = QString("Processing file %1 of %2: %3") .arg(i).arg(total).arg(fileName);
One advantage of using arg() over sprintf() is that the order of arguments may need to change in other languages, when the application is translated.
If there is no place marker (%1, %2, etc.), a warning message is output and the result is undefined. Note that only placeholders between %1 and %99 are supported.
This is an overloaded member function, provided for convenience.
This is the same as str.arg(a1).arg(a2), except that the strings a1 and a2 are replaced in one pass. This can make a difference if a1 contains e.g. %1:
QString str; str = "%1 %2"; str.arg("%1f", "Hello"); // returns "%1f Hello" str.arg("%1f").arg("Hello"); // returns "Hellof %2"
This is an overloaded member function, provided for convenience.
This is the same as calling str.arg(a1).arg(a2).arg(a3), except that the strings a1, a2 and a3 are replaced in one pass.
This is an overloaded member function, provided for convenience.
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4), except that the strings a1, a2, a3 and a4 are replaced in one pass.
This is an overloaded member function, provided for convenience.
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5), except that the strings a1, a2, a3, a4, and a5 are replaced in one pass.
This is an overloaded member function, provided for convenience.
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6)), except that the strings a1, a2, a3, a4, a5, and a6 are replaced in one pass.
This is an overloaded member function, provided for convenience.
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7), except that the strings a1, a2, a3, a4, a5, a6, and a7 are replaced in one pass.
This is an overloaded member function, provided for convenience.
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7).arg(a8), except that the strings a1, a2, a3, a4, a5, a6, a7, and a8 are replaced in one pass.
This is an overloaded member function, provided for convenience.
This is the same as calling str.arg(a1).arg(a2).arg(a3).arg(a4).arg(a5).arg(a6).arg(a7).arg(a8).arg(a9), except that the strings a1, a2, a3, a4, a5, a6, a7, a8, and a9 are replaced in one pass.
This is an overloaded member function, provided for convenience.
The a argument is expressed in base base, which is 10 by default and must be between 2 and 36. For bases other than 10, a is treated as an unsigned integer.
The fieldWidth value specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value will produce a right-aligned number, whereas a negative value will produce a left-aligned number.
The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale, set by QLocale.setDefault(). If no default locale was specified, the "C" locale is used. The 'L' flag is ignored if base is not 10.
QString str; str = QString("Decimal 63 is %1 in hexadecimal") .arg(63, 0, 16); // str == "Decimal 63 is 3f in hexadecimal" QLocale.setDefault(QLocale(QLocale.English, QLocale.UnitedStates)); str = QString("%1 %L2 %L3") .arg(12345) .arg(12345) .arg(12345, 0, 16); // str == "12345 12,345 3039"
This is an overloaded member function, provided for convenience.
The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36.
This is an overloaded member function, provided for convenience.
The fieldWidth value specifies the minimum amount of space that a is padded to and filled with the character fillChar. A positive value will produce a right-aligned number, whereas a negative value will produce a left-aligned number.
The a argument is expressed in the given base, which is 10 by default and must be between 2 and 36.
The '%' can be followed by an 'L', in which case the sequence is replaced with a localized representation of a. The conversion uses the default locale. The default locale is determined from the system's locale settings at application startup. It can be changed using QLocale.setDefault(). The 'L' flag is ignored if base is not 10.
QString str; str = QString("Decimal 63 is %1 in hexadecimal") .arg(63, 0, 16); // str == "Decimal 63 is 3f in hexadecimal" QLocale.setDefault(QLocale(QLocale.English, QLocale.UnitedStates)); str = QString("%1 %L2 %L3") .arg(12345) .arg(12345) .arg(12345, 0, 16); // str == "12345 12,345 3039"
This is an overloaded member function, provided for convenience.
The base argument specifies the base to use when converting the integer a into a string. The base must be between 2 and 36, with 8 giving octal, 10 decimal, and 16 hexadecimal numbers.
Returns the character at the given index position in the string.
The position must be a valid index position in the string (i.e., 0 <= position < size()).
See also operator[]().
Returns the maximum number of characters that can be stored in the string without forcing a reallocation.
The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function. If you want to know how many characters are in the string, call size().
See also reserve() and squeeze().
Removes n characters from the end of the string.
If n is greater than size(), the result is an empty string.
Example:
QString str("LOGOUT\r\n");
str.chop(2);
// str == "LOGOUT"
If you want to remove characters from the beginning of the string, use remove() instead.
See also truncate(), resize(), and remove().
Clears the contents of the string and makes it empty.
See also resize() and isEmpty().
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.
If cs is Qt.CaseSensitive, the comparison is case sensitive; otherwise the comparison is case insensitive.
Case sensitive 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-visible strings with localeAwareCompare().
int x = QString.compare("aUtO", "AuTo", Qt.CaseInsensitive); // x == 0 int y = QString.compare("auto", "Car", Qt.CaseSensitive); // y > 0 int z = QString.compare("auto", "Car", Qt.CaseInsensitive); // z < 0
This function was introduced in Qt 4.2.
See also operator==(), operator<(), and operator>().
This is an overloaded member function, provided for convenience.
Performs a case sensitive compare of s1 and s2.
This is an overloaded member function, provided for convenience.
Performs a comparison of s1 and s2, using the case sensitivity setting cs.
This function was introduced in Qt 4.2.
This is an overloaded member function, provided for convenience.
Performs a comparison of s1 and s2, using the case sensitivity setting cs.
This function was introduced in Qt 4.2.
This is an overloaded member function, provided for convenience.
Lexically compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.
Equivalent to compare(*this, other).
This is an overloaded member function, provided for convenience.
Same as compare(*this, other, cs).
This function was introduced in Qt 4.2.
This is an overloaded member function, provided for convenience.
Same as compare(*this, other, cs).
This function was introduced in Qt 4.2.
Returns true if this string contains an occurrence of the string str; otherwise returns false.
If cs is Qt.CaseSensitive (the default), the search is case sensitive; otherwise the search is case insensitive.
Example:
QString str = "Peter Pan";
str.contains("peter", Qt.CaseInsensitive); // returns true
See also indexOf() and count().
Returns the number of (potentially overlapping) occurrences of the string str in this string.
If cs is Qt.CaseSensitive (the default), the search is case sensitive; otherwise the search is case insensitive.
See also contains() and indexOf().
This is an overloaded member function, provided for convenience.
Returns the number of occurrences of character ch in the string.
This is an overloaded member function, provided for convenience.
Returns the number of times the regular expression rx matches in the string.
This function counts overlapping matches, so in the example below, there are four instances of "ana" or "ama":
QString str = "banana and panama";
str.count(QRegExp("a[nm]a")); // returns 4
Returns true if the string ends with s; otherwise returns false.
If cs is Qt.CaseSensitive (the default), the search is case sensitive; otherwise the search is case insensitive.
QString str = "Bananas"; str.endsWith("anas"); // returns true str.endsWith("pple"); // returns false
See also startsWith().
Sets every character in the string to character ch. If size is different from -1 (the default), the string is resized to size beforehand.
Example:
QString str = "Berlin"; str.fill('z'); // str == "zzzzzz" str.fill('A', 2); // str == "AA"
See also resize().
Returns a QString initialized with the first size characters of the 8-bit ASCII string str.
If size is -1 (the default), it is taken to be qstrlen(str).
If a codec has been set using QTextCodec.setCodecForCStrings(), it is used to convert str to Unicode; otherwise this function does the same as fromLatin1().
See also toAscii(), fromLatin1(), fromUtf8(), and fromLocal8Bit().
Returns a QString initialized with the first size characters of the Latin-1 string str.
If size is -1 (the default), it is taken to be qstrlen(str).
See also toLatin1(), fromAscii(), fromUtf8(), and fromLocal8Bit().
Returns a QString initialized with the first size characters of the 8-bit string str.
If size is -1 (the default), it is taken to be qstrlen(str).
QTextCodec.codecForLocale() is used to perform the conversion from Unicode.
See also toLocal8Bit(), fromAscii(), fromLatin1(), and fromUtf8().
Returns a QString initialized with the first size bytes of the UTF-8 string str.
If size is -1 (the default), it is taken to be qstrlen(str).
See also toUtf8(), fromAscii(), fromLatin1(), and fromLocal8Bit().
Returns the index position of the first occurrence of the string str in this string, searching forward from index position from. Returns -1 if str is not found.
If cs is Qt.CaseSensitive (the default), the search is case sensitive; otherwise the search is case insensitive.
Example:
QString x = "sticky question"; QString y = "sti"; x.indexOf(y); // returns 0 x.indexOf(y, 1); // returns 10 x.indexOf(y, 10); // returns 10 x.indexOf(y, 11); // returns -1
If from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.
See also lastIndexOf(), contains(), and count().
This is an overloaded member function, provided for convenience.
Returns the index position of the first occurrence of the character ch in the string, searching forward from index position from. Returns -1 if ch could not be found.
Inserts the string str at the given index position and returns a reference to this string.
Example:
QString str = "Meal";
str.insert(1, QString("ontr"));
// str == "Montreal"
If the given position is greater than size(), the array is first extended using resize().
See also append(), prepend(), replace(), and remove().
This is an overloaded member function, provided for convenience.
Inserts the Latin-1 string str at the given index position.
Returns true if the string has no characters; otherwise returns false.
Example:
QString().isEmpty(); // returns true QString("").isEmpty(); // returns true QString("x").isEmpty(); // returns false QString("abc").isEmpty(); // returns false
See also size().
Returns true if this string is null; otherwise returns false.
Example:
QString().isNull(); // returns true QString("").isNull(); // returns false QString("abc").isNull(); // returns false
Qt makes a distinction between null strings and empty strings for historical reasons. For most applications, what matters is whether or not a string contains any data, and this can be determined using the isEmpty() function.
See also isEmpty().
Returns the index position of the last occurrence of the string str in this string, searching backward from index position from. If from is -1 (the 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 (the default), the search is case sensitive; otherwise the search is case insensitive.
Example:
QString x = "crazy azimuths"; QString y = "az"; x.lastIndexOf(y); // returns 6 x.lastIndexOf(y, 6); // returns 6 x.lastIndexOf(y, 5); // returns 2 x.lastIndexOf(y, 1); // returns -1
See also indexOf(), contains(), and count().
This is an overloaded member function, provided for convenience.
Returns the index position of the last occurrence of the character ch, searching backward from position from.
Returns a substring that contains the n leftmost characters of the string.
The entire string is returned if n is greater than size() or less than zero.
QString x = "Pineapple";
QString y = x.left(4); // y == "Pine"
See also right(), mid(), and startsWith().
Returns a string of size width that contains this string padded by the fill character.
If truncate is false and the size() of the string is more than width, then the returned string is a copy of the string.
QString s = "apple";
QString t = s.leftJustified(8, '.'); // t == "apple..."
If truncate is true and the size() of the string is more than width, then any characters in a copy of the string after position width are removed, and the copy is returned.
QString str = "Pineapple";
str = str.leftJustified(5, '.', true); // str == "Pinea"
See also rightJustified().
Returns the number of characters in this string. Equivalent to size().
See also setLength().
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.
On Mac OS X since Qt 4.3, this function compares according the "Order for sorted lists" setting in the International prefereces panel.
See also compare() and QTextCodec.locale().
This is an overloaded member function, provided for convenience.
Compares this string with the other string and returns an integer less than, equal to, or greater than zero if this string is less than, equal to, or greater than the other string.
Same as localeAwareCompare(*this, other).
Returns a string that contains n characters of this string, starting at the specified position index.
Returns a null string if the position index exceeds the length of the string. If there are less than n characters available in the string starting at the given position, or if n is -1 (the default), the function returns all characters that are available from the specified position.
Example:
QString x = "Nine pineapples"; QString y = x.mid(5, 4); // y == "pine" QString z = x.mid(5); // z == "pineapples"
Returns the string in the given Unicode normalization mode.
This is an overloaded member function, provided for convenience.
Returns the string in the given Unicode normalization mode, according to the given version of the Unicode standard.
Returns a string equivalent of the number n according to the specified base.
The base is 10 by default and must be between 2 and 36. For bases other than 10, n is treated as an unsigned integer.
long a = 63; QString s = QString.number(a, 16); // s == "3f" QString t = QString.number(a, 16).toUpper(); // t == "3F"
See also setNum().
This is an overloaded member function, provided for convenience.
This is an overloaded member function, provided for convenience.
This is an overloaded member function, provided for convenience.
Prepends the string str to the beginning of this string and returns a reference to this string.
Example:
QString x = "ship";
QString y = "air";
x.prepend(y);
// x == "airship"
See also append() and insert().
This is an overloaded member function, provided for convenience.
Prepends the Latin-1 string str to this string.
This is an overloaded member function, provided for convenience.
Prepends the byte array ba to this string. The byte array is converted to Unicode using the fromAscii() function.
You can disable this function 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 is provided for STL compatibility, appending the given other string onto the end of this string. It is equivalent to append(other).
See also append().
This function is provided for STL compatibility, prepending the given other string to the beginning of this string. It is equivalent to prepend(other).
See also prepend().
Removes n characters from the string, starting at the given position index, and returns a reference to the string.
If the specified position index is within the string, but position + n is beyond the end of the string, the string is truncated at the specified position.
QString s = "Montreal";
s.remove(1, 4);
// s == "Meal"
See also insert() and replace().
Replaces n characters from the specified index position with the string after, and returns a reference to this string.
Example:
QString x = "Say yes!";
QString y = "no";
x.replace(4, 3, y);
// x == "Say no!"
See also insert() and remove().
Attempts to allocate memory for at least size characters. If you know in advance how large the string will be, you can call this function, and if you resize the string often you are likely to get better performance. If size is an underestimate, the worst that will happen is that the QString will be a bit slower.
The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function. If you want to change the size of the string, call resize().
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 large enough to make a call to reserve() worthwhile:
QString result; int maxSize; bool condition; QChar nextChar; result.reserve(maxSize); while (condition) result.append(nextChar); result.squeeze();
See also squeeze() and capacity().
Sets the size of the string to size characters.
If size is greater than the current size, the string is extended to make it size characters long with the extra characters added to the end. The new characters are uninitialized.
If size is less than the current size, characters are removed from the end.
Example:
QString s = "Hello world"; s.resize(5); // s == "Hello" s.resize(8); // s == "Hello???" (where ? stands for any character)
If you want to append a certain number of identical characters to the string, use operator+=() as follows rather than resize():
QString t = "Hello";
t += QString(10, 'X');
// t == "HelloXXXXXXXXXX"
If you want to expand the string so that it reaches a certain width and fill the new positions with a particular character, use the leftJustified() function:
If size is negative, it is equivalent to passing zero.
QString r = "Hello";
r = r.leftJustified(10, ' ');
// r == "Hello "
See also truncate() and reserve().
Returns a substring that contains the n rightmost characters of the string.
The entire string is returned if n is greater than size() or less than zero.
QString x = "Pineapple";
QString y = x.right(5); // y == "apple"
See also left(), mid(), and endsWith().
Returns a string of size() width that contains the fill character followed by the string. For example:
QString s = "apple";
QString t = s.rightJustified(8, '.'); // t == "...apple"
If truncate is false and the size() of the string is more than width, then the returned string is a copy of the string.
If truncate is true and the size() of the string is more than width, then the resulting string is truncated at position width.
QString str = "Pineapple";
str = str.rightJustified(5, '.', true); // str == "Pinea"
See also leftJustified().
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. Fields are numbered 0, 1, 2, etc., counting from the left, and -1, -2, etc., counting from right to left.
The flags argument can be used to affect some aspects of the function's behavior, e.g. whether to be case sensitive, whether to skip empty fields and how to deal with leading and trailing separators; see SectionFlags.
QString str; QString csv = "forename,middlename,surname,phone"; QString path = "/usr/local/bin/myapp"; // First field is empty QString.SectionFlag flag = QString.SectionSkipEmpty; str = csv.section(',', 2, 2); // str == "surname" str = path.section('/', 3, 4); // str == "bin/myapp" str = path.section('/', 3, 3, flag); // str == "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.
str = csv.section(',', -3, -2); // str == "middlename,surname" str = path.section('/', -1); // str == "myapp"
See also split().
This is an overloaded member function, provided for convenience.
QString str; QString data = "forename**middlename**surname**phone"; str = data.section("**", 2, 2); // str == "surname" str = data.section("**", -3, -2); // str == "middlename**surname"
See also split().
Sets the string to the printed value of n in the specified base, and returns a reference to the string.
The base is 10 by default and must be between 2 and 36. For bases other than 10, n is treated as an unsigned integer.
QString str;
str.setNum(1234); // str == "1234"
The formatting follows the current locale.
This is an overloaded member function, provided for convenience.
This is an overloaded member function, provided for convenience.
This is an overloaded member function, provided for convenience.
Returns a string that has whitespace removed from the start and the end, and that has each sequence of internal whitespace replaced with a single space.
Whitespace means any character for which QChar.isSpace() returns true. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.
Example:
QString str = " lots\t of\nwhitespace\r\n ";
str = str.simplified();
// str == "lots of whitespace";
See also trimmed().
Returns the number of characters in this string.
The last character in the string is at position size() - 1. In addition, QString ensures that the character at position size() is always '\0', so that you can use the return value of data() and constData() as arguments to functions that expect '\0'-terminated strings.
Example:
QString str = "World"; int n = str.size(); // n == 5 str.data()[0]; // returns 'W' str.data()[4]; // returns 'd' str.data()[5]; // returns '\0'
See also isEmpty() and resize().
Splits the string into substrings wherever sep occurs, and returns the list of those strings. If sep does not match anywhere in the string, split() returns a single-element list containing this string.
cs specifies whether sep should be matched case sensitively or case insensitively.
If behavior is QString.SkipEmptyParts, empty entries don't appear in the result. By default, empty entries are kept.
Example:
QString str = "a,,b,c"; QStringList list1 = str.split(","); // list1: [ "a", "", "b", "c" ] QStringList list2 = str.split(",", QString.SkipEmptyParts); // list2: [ "a", "b", "c" ]
See also QStringList.join() and section().
This is an overloaded member function, provided for convenience.
Releases any memory not required to store the character data.
The sole purpose of this function is to provide a means of fine tuning QString's memory usage. In general, you will rarely ever need to call this function.
See also reserve() and capacity().
Returns true if the string starts with s; otherwise returns false.
If cs is Qt.CaseSensitive (the default), the search is case sensitive; otherwise the search is case insensitive.
QString str = "Bananas"; str.startsWith("Ban"); // returns true str.startsWith("Car"); // returns false
See also endsWith().
Returns an 8-bit ASCII representation of the string as a QByteArray.
If a codec has been set using QTextCodec.setCodecForCStrings(), it is used to convert Unicode to 8-bit char; otherwise this function does the same as toLatin1().
See also fromAscii(), toLatin1(), toUtf8(), toLocal8Bit(), and QTextCodec.
Returns the case folded equivalent of the string. For most Unicode characters this is the same as toLower().
Returns the string converted to a double value.
Returns 0.0 if the conversion fails.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true.
QString str = "1234.56";
double val = str.toDouble(); // val == 1234.56
Various string formats for floating point numbers can be converted to double values:
bool ok;
double d;
d = QString( "1234.56e-02" ).toDouble(&ok); // ok == true, d == 12.3456
This function tries to interpret the string according to the current locale. The current locale is determined from the system at application startup and can be changed by calling QLocale.setDefault(). If the string cannot be interpreted according to the current locale, this function falls back on the "C" locale.
QLocale.setDefault(QLocale.C); d = QString( "1234,56" ).toDouble(&ok); // ok == false d = QString( "1234.56" ).toDouble(&ok); // ok == true, d == 1234.56 QLocale.setDefault(QLocale.German); d = QString( "1234,56" ).toDouble(&ok); // ok == true, d == 1234.56 d = QString( "1234.56" ).toDouble(&ok); // ok == true, d == 1234.56
Due to the ambiguity between the decimal point and thousands group separator in various locales, this function does not handle thousands group separators. If you need to convert such numbers, see QLocale.toDouble().
QLocale.setDefault(QLocale.C);
d = QString( "1234,56" ).toDouble(&ok); // ok == false
See also number(), QLocale.setDefault(), QLocale.toDouble(), and trimmed().
Returns the string converted to a float value.
If a conversion error occurs, *ok is set to false; otherwise *ok is set to true. Returns 0.0 if the conversion fails.
Example:
QString str1 = "1234.56"; str1.toFloat(); // returns 1234.56 bool ok; QString str2 = "R2D2"; str2.toFloat(&ok); // returns 0.0, sets ok to false
See also number(), toDouble(), and toInt().
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 a conversion error occurs, *ok is set to false; otherwise *ok is set 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.
Example:
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(), toUInt(), and toDouble().
Returns a Latin-1 representation of the string as a QByteArray. The returned byte array is undefined if the string contains non-Latin1 characters.
See also fromLatin1(), toAscii(), toUtf8(), toLocal8Bit(), and QTextCodec.
Returns the local 8-bit representation of the string as a QByteArray. The returned byte array is undefined if the string contains characters not supported by the local 8-bit encoding.
QTextCodec.codecForLocale() is used to perform the conversion from Unicode.
See also fromLocal8Bit(), toAscii(), toLatin1(), toUtf8(), and QTextCodec.
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 a conversion error occurs, *ok is set to false; otherwise *ok is set 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.
Example:
QString str = "FF"; bool ok; long hex = str.toLong(&ok, 16); // hex == 255, ok == true long dec = str.toLong(&ok, 10); // dec == 0, ok == false
See also number(), toULong(), and toInt().
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 a conversion error occurs, *ok is set to false; otherwise *ok is set 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.
Example:
QString str = "FF"; bool ok; long hex = str.toLongLong(&ok, 16); // hex == 255, ok == true long dec = str.toLongLong(&ok, 10); // dec == 0, ok == false
See also number(), toULongLong(), and toInt().
Returns a lowercase copy of the string.
QString str = "TROlltECH";
str = str.toLower(); // str == "trolltech"
See also toUpper().
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 a conversion error occurs, *ok is set to false; otherwise *ok is set 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.
Example:
QString str = "FF"; bool ok; short hex = str.toShort(&ok, 16); // hex == 255, ok == true short dec = str.toShort(&ok, 10); // dec == 0, ok == false
See also number(), toUShort(), and toInt().
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 a conversion error occurs, *ok is set to false; otherwise *ok is set 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.
Example:
QString str = "FF"; bool ok; uint hex = str.toUInt(&ok, 16); // hex == 255, ok == true uint dec = str.toUInt(&ok, 10); // dec == 0, ok == false
See also number() and toInt().
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 a conversion error occurs, *ok is set to false; otherwise *ok is set 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.
Example:
QString str = "FF"; bool ok; ulong hex = str.toULong(&ok, 16); // hex == 255, ok == true ulong dec = str.toULong(&ok, 10); // dec == 0, ok == false
See also number().
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 a conversion error occurs, *ok is set to false; otherwise *ok is set 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.
Example:
QString str = "FF"; bool ok; unsigned long hex = str.toULongLong(&ok, 16); // hex == 255, ok == true unsigned long dec = str.toULongLong(&ok, 10); // dec == 0, ok == false
See also number() and toLongLong().
Returns an uppercase copy of the string.
QString str = "TeXt";
str = str.toUpper(); // str == "TEXT"
See also toLower().
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 a conversion error occurs, *ok is set to false; otherwise *ok is set 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.
Example:
QString str = "FF"; bool ok; ushort hex = str.toUShort(&ok, 16); // hex == 255, ok == true ushort dec = str.toUShort(&ok, 10); // dec == 0, ok == false
See also number() and toShort().
Returns a UTF-8 representation of the string as a QByteArray.
See also fromUtf8(), toAscii(), toLatin1(), toLocal8Bit(), and QTextCodec.
Returns a string that has whitespace removed from the start and the end.
Whitespace means any character for which QChar.isSpace() returns true. This includes the ASCII characters '\t', '\n', '\v', '\f', '\r', and ' '.
Example:
QString str = " lots\t of\nwhitespace\r\n ";
str = str.trimmed();
// str == "lots\t of\nwhitespace"
Unlike simplified(), trimmed() leaves internal whitespace alone.
See also simplified().
Truncates the string at the given position index.
If the specified position index is beyond the end of the string, nothing happens.
Example:
QString str = "Vladivostok";
str.truncate(4);
// str == "Vlad"
If position is negative, it is equivalent to passing zero.
See also chop(), resize(), and left().
PyQt 4.4.4 for Windows | Copyright © Riverbank Computing Ltd and Trolltech AS 2008 | Qt 4.4.2 |