The QString class provides an abstraction of the classic C zero-terminated char array (char*). More...
#include <qstring.h>
Inherits QByteArray.
QString inherits QByteArray, which is defined as QArray<char>.
Since QString is a QArray, it uses explicit sharing with a reference count.
Note that for the QString methods that take a const char * parameter the results are undefined if the QString is not zero-terminated. It is legal for the const char * parameter to be 0.
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.
See also: Shared classes
Examples: table/table.cpp dclock/dclock.cpp grapher/grapher.cpp forever/forever.cpp dirview/dirview.cpp desktop/desktop.cpp tooltip/tooltip.cpp drawdemo/drawdemo.cpp movies/main.cpp picture/picture.cpp xform/xform.cpp application/application.cpp pref/pref.cpp progress/progress.cpp layout/layout.cpp qmag/qmag.cpp showimg/showimg.cpp biff/biff.cpp widgets/widgets.cpp
Constructs a null string.
See also: isNull().
Constructs a shallow copy s.
See also: assign().
Constructs a string that is a deep copy of str.
If str is 0 a null string is created.
See also: isNull().
Constructs a string that is a deep copy of str, that is no more than maxlen bytes long including the '\0'-terminator.
Example:
QString str("helloworld",6); // Assigns "hello" to str.
If str contains a 0 byte within the first maxlen bytes, the resulting QString will be terminated by the 0. If str is 0 a null string is created.
See also: isNull().
Constructs a string with room for size characters, including the '\0'-terminator. Makes a null string if size == 0.
If size > 0, then the first and last characters in the string are initialized to '\0'. All other characters are uninitialized.
See also: resize() and isNull().
Returns the string data.
Appends str to the string and returns a reference to the string. Equivalent to operator+=().
Examples: dirview/dirview.cpp
Returns the number of times the character c occurs in the string.
The match is case sensitive if cs is TRUE, or case insensitive if cs if FALSE.
Counts the number of overlapping occurrences of rx in the string.
Example:
QString s = "banana and panama";
QRegExp r = QRegExp("a[nm]a", TRUE, FALSE);
s.contains( r ); // 4 matches
See also: find() and findRev().
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 substrings, for example, "banana" contains two occurrences of "ana".
See also: findRev().
Returns a deep copy of this string.
See also: detach().
Fills the string with len bytes of value c, followed by a '\0'-terminator.
If len is negative, then the current string length is used.
Returns FALSE is len is nonnegative and there is no memory to resize the string, otherwise TRUE is returned.
Finds the first occurrence of the character c, starting at position index.
The search is case sensitive if cs is TRUE, or case insensitive if cs is FALSE.
Returns the position of c, or -1 if c could not be found.
Finds the first occurrence of the regular expression rx, starting at position index.
Returns the position of the next match, or -1 if rx was not found.
Finds the first occurrence of the string str, starting at position index.
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.
Finds the first occurrence of the character c, starting at position index and searching backwards.
The search is case sensitive if cs is TRUE, or case insensitive if cs is FALSE.
Returns the position of c, or -1 if c could not be found.
Finds the first occurrence of the regular expression rx, starting at position index and searching backwards.
The search will start from the end of the string if index is negative.
Returns the position of the next match (backwards), or -1 if rx was not found.
Finds the first occurrence of the string str, starting at position index and 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.
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.
Example:
QString s = "Yes";
s.insert( 3, '!'); // s == "Yes!"
See also: remove() and replace().
Insert s into the string before position index.
If index is beyond the end of the string, the string is extended with spaces (ASCII 32) to length index and s is then appended.
QString s = "I like fish";
s.insert( 2, "don't "); // s == "I don't like fish"
s = "x";
s.insert( 3, "yz" ); // s == "x yz"
Examples: xform/xform.cpp
Returns TRUE if the string is empty, i.e. if length() == 0. An empty string is not always a null string.
See example in isNull().
See also: isNull(), length() and size().
Examples: application/application.cpp qmag/qmag.cpp showimg/showimg.cpp
Returns TRUE if the string is null, i.e. if data() == 0. A null string is also an empty string.
Example:
QString a; // a.data() == 0, a.size() == 0, a.length() == 0
QString b == ""; // b.data() == "", b.size() == 1, b.length() == 0
a.isNull(); // TRUE, because a.data() == 0
a.isEmpty(); // TRUE, because a.length() == 0
b.isNull(); // FALSE, because b.data() == ""
b.isEmpty(); // TRUE, because b.length() == 0
See also: isEmpty(), length() and size().
Returns a substring that contains the len leftmost characters of the string.
The whole string is returned if len exceeds the length of the string.
Example:
QString s = "Pineapple";
QString t = s.left( 4 ); // t == "Pine"
Returns a string of length width (plus '\0') that contains this string and padded by the fill character.
If the length of the string exceeds width and truncate is FALSE, then the returned string is a copy of the string. If the length of the string exceeds width and truncate is TRUE, then the returned string is a left(width).
Example:
QString s("apple");
QString t = s.leftJustify(8, '.'); // t == "apple..."
See also: rightJustify().
Returns the length of the string, excluding the '\0'-terminator.
Equivalent to calling strlen(data()).
Null strings and empty strings have zero length.
See also: size(), isNull() and isEmpty().
Examples: showimg/showimg.cpp
Returns a new string that is the string converted to lower case.
Presently it only handles 7-bit ASCII, or whatever tolower() handles (if $LC_CTYPE is set, most UNIX systems do the Right Thing).
Example:
QString s("TeX");
QString t = s.lower(); // t == "tex"
See also: upper().
Returns a substring that contains the len characters of this string, starting at position index.
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.
Example:
QString s = "Two pineapples";
QString t = s.mid( 4, 4 ); // t == "pine"
Examples: qmag/qmag.cpp
Appends c to the string and returns a reference to the string.
Appends str 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.
Assigns a deep copy of str to this string and returns a reference to this string.
If str is 0 a null string is created.
See also: isNull().
Prepend \s to the string. Equivalent to insert(0,s).
See also: insert().
Removes len characters starting at position index from the string and returns a reference to the string.
If index is too big, nothing happens. If index is valid, but len is too large, the rest of the string is removed.
QString s = "Montreal";
s.remove( 1, 4 );
// s == "Meal"
See also: insert() and replace().
Replaces every occurrence of rx in the string with str. Returns a reference to the string.
Example:
QString s = "banana";
s.replace( QRegExp("a.*a"), "" ); // becomes "b"
QString s = "banana";
s.replace( QRegExp("^[bn]a"), " " ); // becomes " nana"
QString s = "banana";
s.replace( QRegExp("^[bn]a"), "" ); // NOTE! becomes ""
Examples: qmag/qmag.cpp
Replaces len characters starting at position index from the string with s, and returns a reference to the string.
If index is too big, nothing is deleted and s is inserted at the end of the string. If index is valid, but len is too large, str replaces the rest of the string.
QString s = "Say yes!";
s.replace( 4, 3, "NO" ); // s == "Say NO!"
See also: insert() and remove().
Extends or shrinks the string to len bytes, including the '\0'-terminator.
A \0-terminator is set at position len - 1 unless
len == 0.
Example:
QString s = "resize this string";
s.resize( 7 ); // s == "resize"
See also: truncate().
Returns a substring that contains the len rightmost characters of the string.
The whole string is returned if len exceeds the length of the string.
Example:
QString s = "Pineapple";
QString t = s.right( 5 ); // t == "apple"
Returns a string of length width (plus '\0') that contains pad characters followed by the string.
If the length of the string exceeds width and truncate is FALSE, then the returned string is a copy of the string. If the length of the string exceeds width and truncate is TRUE, then the returned string is a right(width).
Example:
QString s("pie");
QString t = s.rightJustify(8, '.'); // t == ".....pie"
See also: leftJustify().
Sets the character at position index to c and expands the string if necessary, filling with spaces.
Returns FALSE if this index was out of range and the string could not be expanded, otherwise TRUE.
Sets the string to the printed value of n.
Arguments:
Sets the string to the printed value of n.
Arguments:
Sets the string to the printed value of n and returns a reference to the string.
Sets the string to the printed value of n and returns a reference to the string.
Sets the string to the printed value of n and returns a reference to the string.
Sets the string to the printed unsigned value of n and returns a reference to the string.
Sets the string to the printed unsigned value of n and returns a reference to the string.
Sets the string to the printed unsigned value of n and returns a reference to the string.
Makes a deep copy of str. Returns a reference to the string.
Returns a new string that has white space removed from the start and the end, plus any sequence of internal white space replaced with a single space (ASCII 32).
White space means any ASCII code 9, 10, 11, 12, 13 or 32.
QString s = " lots\t of\nwhite space ";
QString t = s.simplifyWhiteSpace(); // t == "lots of white space"
See also: stripWhiteSpace().
Implemented as a call to the native vsprintf() (see your C-library manual).
If your string is shorter than 256 characters, this sprintf() calls resize(256) to decrease the chance of memory corruption. The string is resized back to its natural length before sprintf() returns.
Example:
QString s;
s.sprintf( "%d - %s", 1, "first" ); // result < 256 chars
QString big( 25000 ); // very long string
big.sprintf( "%d - %s", 2, longString ); // result < 25000 chars
Warning: All vsprintf() implementations will write past the end of the target string (*this) if the format specification and arguments happen to be longer than the target string, and some will also fail if the target string is longer than some arbitrary implementation limit.
Giving user-supplied arguments to sprintf() is begging for trouble. Sooner or later someone will paste a 3000-character line into your application.
Examples: dclock/dclock.cpp forever/forever.cpp tooltip/tooltip.cpp drawdemo/drawdemo.cpp movies/main.cpp picture/picture.cpp xform/xform.cpp application/application.cpp pref/pref.cpp progress/progress.cpp layout/layout.cpp qmag/qmag.cpp showimg/showimg.cpp widgets/widgets.cpp
Returns a new string that has white space removed from the start and the end.
White space means any ASCII code 9, 10, 11, 12, 13 or 32.
Example:
QString s = " space ";
QString t = s.stripWhiteSpace(); // t == "space"
See also: simplifyWhiteSpace().
Returns the string converted to a double value.
If ok is non-null, *ok is set to TRUE if there are no conceivable errors, and FALSE if the string is not a number at all, or if it has trailing garbage.
Returns the string converted to a float value.
If ok is non-null, *ok is set to TRUE if there are no conceivable errors, and FALSE if the string is not a number at all, or if it has trailing garbage.
Returns the string converted to a int value.
If ok is non-null, *ok is set to TRUE if there are no conceivable errors, and FALSE if the string is not a number at all, or if it has trailing garbage.
Returns the string converted to a long value.
If ok is non-null, *ok is set to TRUE if there are no conceivable errors, and FALSE if the string is not a number at all, or if it has trailing garbage.
Returns the string converted to a short value.
If ok is non-null, *ok is set to TRUE if there are no conceivable errors, and FALSE if the string is not a number at all, or if it has trailing garbage.
Returns the string converted to an unsigned int value.
If ok is non-null, *ok is set to TRUE if there are no conceivable errors, and FALSE if the string is not a number at all, or if it has trailing garbage.
Returns the string converted to an unsigned long
value.
If ok is non-null, *ok is set to TRUE if there are no conceivable errors, and FALSE if the string is not a number at all, or if it has trailing garbage.
Returns the string converted to an unsigned short value.
If ok is non-null, *ok is set to TRUE if there are no conceivable errors, and FALSE if the string is not a number at all, or if it has trailing garbage.
Truncates the string at position pos.
Equivalent to calling resize(pos+1).
Example:
QString s = "truncate this string";
s.truncate( 5 ); // s == "trunc"
See also: resize().
Returns a new string that is the string converted to upper case.
Presently it only handles 7-bit ASCII, or whatever toupper() handles (if $LC_CTYPE is set, most UNIX systems do the Right Thing).
Example:
QString s("TeX");
QString t = s.upper(); // t == "TEX"
See also: lower().
This function is normally part of the C library. Qt implements memmove() for platforms that do not have it.
memmove() copies len bytes from src into dst. The data is copied correctly even if src and dst overlap.
Returns a duplicate string.
Allocates space for a copy of str (using new), copies it, and returns
a pointer to the copy.
If src is null, it immediately returns 0.
A safe strlen() function that overrides the one defined by the C library. The original strlen() function has been renamed cstrlen().
Returns the number of characters in str, or 0 if str is null.
A safe strcpy() function that overrides the one defined by the C library. The original strcpy() function has been renamed cstrcpy().
Copies all characters (including \0) from str into dst and returns a pointer to dst. If src is null, it immediately returns 0.
See also: qstrncpy().
A safe strncpy() function.
Copies all characters up to len bytes from str into dst and returns a pointer to dst. Guarantees that dst is \0-terminated. If src is null, it immediately returns 0.
See also: strcpy().
A safe strcmp() function that overrides the one defined by the C library. The original strcmp() function has been renamed cstrcmp().
Compares str1 and str2. Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.
Special case I: Returns 0 if str1 and str2 are both null.
Special case II: Returns a random nonzero value if str1 is null or str2 is null (but not both).
See also: strncmp(), stricmp() and strnicmp().
Examples: desktop/desktop.cpp
A safe strncmp() function that overrides the one defined by the C library. The original strncmp() function has been renamed cstrncmp().
Compares str1 and str2 up to len bytes.
Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.
Special case I: Returns 0 if str1 and str2 are both null.
Special case II: Returns a random nonzero value if str1 is null or str2 is null (but not both).
See also: strcmp(), stricmp() and strnicmp().
A safe stricmp() function that overrides the one defined by the C library, if the C library has one.
Compares str1 and str2 ignoring the case.
Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.
Special case I: Returns 0 if str1 and str2 are both null.
Special case II: Returns a random nonzero value if str1 is null or str2 is null (but not both).
See also: strcmp(), strncmp() and strnicmp().
A safe strnicmp() function that overrides the one defined by the C library, if the C library has one.
Compares str1 and str2 up to len bytes ignoring the case.
Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.
Special case I: Returns 0 if str1 and str2 are both null.
Special case II: Returns a random nonzero value if str1 is null or str2 is null (but not both).
See also: strcmp(), strncmp() and stricmp().
Writes a string to the stream.
Output format: [length (Q_UINT32) data...].
Reads a string from the stream.
Returns TRUE if the two strings are equal, or FALSE if they are different.
Equivalent to strcmp(s1,s2) == 0
Returns TRUE if the two strings are equal, or FALSE if they are different.
Equivalent to strcmp(s1,s2) == 0
Returns TRUE if the two strings are equal, or FALSE if they are different.
Equivalent to strcmp(s1,s2) == 0
Returns TRUE if the two strings are different, or FALSE if they are equal.
Equivalent to strcmp(s1,s2) != 0
Returns TRUE if the two strings are different, or FALSE if they are equal.
Equivalent to strcmp(s1,s2) != 0
Returns TRUE if the two strings are different, or FALSE if they are equal.
Equivalent to strcmp(s1,s2) != 0
Returns TRUE if s1 is alphabetically less than s2, otherwise FALSE.
Equivalent to strcmp(s1,s2) < 0
Returns TRUE if s1 is alphabetically less than s2, otherwise FALSE.
Equivalent to strcmp(s1,s2) < 0
Returns TRUE if s1 is alphabetically less than or equal to s2, otherwise FALSE.
Equivalent to strcmp(s1,s2) <= 0
Returns TRUE if s1 is alphabetically less than or equal to s2, otherwise FALSE.
Equivalent to strcmp(s1,s2) <= 0
Returns TRUE if s1 is alphabetically greater than s2, otherwise FALSE.
Equivalent to strcmp(s1,s2) > 0
Returns TRUE if s1 is alphabetically greater than s2, otherwise FALSE.
Equivalent to strcmp(s1,s2) > 0
Returns TRUE if s1 is alphabetically greater than or equal to s2, otherwise FALSE.
Equivalent to strcmp(s1,s2) >= 0
Returns TRUE if s1 is alphabetically greater than or equal to s2, otherwise FALSE.
Equivalent to strcmp(s1,s2) >= 0
Returns the concatenated string of s1 and s2.
Returns the concatenated string of s1 and s2.
Returns the concatenated string of s1 and s2.
Returns the concatenated string of s and c.
Returns the concatenated string of c and s.
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