Chapter 1

SetLength() allows the length to be specified to anything within range 0 to MaxLength(),
and SetMax() sets the length to the maximum length.
Various Fill() functions allow a descriptor to be filled with data quickly.
5.3.6 Manipulating Data
TDes's Copy() function copies data to the descriptor, starting at the beginning, while
Append() can copy additional data to the descriptor, starting where the existing data stops.
There are variants of the Copy()function that perform case or accent folding.
Insert() inserts data into any position, pushing up subsequent characters toward the end
of the string. Delete() deletes any sequence of characters, moving down subsequent
characters to close the gap. Replace() overwrites characters in the middle of a string.
5.3.7 Letter Manipulation
TDes's Fold(), Collate(), LowerCase(), UpperCase(), and Capitalize() functions all
manipulate characters in place.
Note
Collating an individual string isn't very useful, and TDes::Collate() is
therefore deprecated.
5.3.8 Trimming and Justification
TDes's Trim() functions shave whitespace from either or both ends of a string.
Justify() performs left, right, center, or no justification and allows the fill character to be
overridden. Various AppendJustify()functions append and justify simultaneously.
Note
Justify() is not really very useful, since real text justification is done at the
GUI level, not the individual string level.
5.3.9 Formatting
TDes::AppendFormat() is a bit like C sprintf(): it takes a format string and a variable
argument list and appends the result to an existing descriptor. Functions such as Format()
are implemented in terms of this one as was CConsoleBase::Printf(), which we saw in
hellotext and strings.
Many lower-level functions exist to support AppendFormat(): various Num() functions
convert numbers into text, and corresponding AppendNum() functions append converted
numbers onto an existing descriptor. For simple conversions, the AppendNum() functions
are much more efficient than using AppendFormat() with a suitable format string.
In C, scanning functions are provided by sscanf() and packaged variants such as
scanf(), fscanf() and so on. Similar functions are available in Symbian OS, through
TLex and associated classes, which scan data held in TDesCs. These functions are
relatively specialized and it was not thought appropriate to implement them directly in
TDesC.