Manipulating Mutable String Objects
You can choose from a variety of string object functions to add to and modify the contents of mutable CFString
objects. These functions, as one might expect, do not work on immutable CFString
objects. If you want to change the contents of a CFString
object, you must either start with a content-less mutable CFString
object or make a mutable copy of an immutable CFString
object. See Creating Mutable String Objects for information on creating objects of this kind.
Forms of Mutation
The functions that manipulate mutable CFString
objects fall into several categories, described in the following sections.
Appending
You can append strings in a variety of formats to a mutable CFString
object: other CFString
objects (CFStringAppend
), C strings (CFStringAppendCString
), Unicode characters (CFStringAppendCharacters
), and formatted strings (CFStringAppendFormat
and CFStringAppendFormatAndArguments
).
Inserting, deleting, replacing
The functions CFStringInsert
, CFStringDelete
, and CFStringReplace
perform the corresponding operations. These functions require you to specify a zero-based index into, or range of, the string to be modified.
Padding and trimming
The CFStringPad
function extends or truncates a mutable CFString
to a given length; if it extends the string, it pads with a specified character or characters. The CFStringTrim
function trims a specific character from both sides of the string. For example, the call:
CFStringTrim(CFStringCreateMutableCopy(NULL, NULL, CFSTR("xxxabcx")), CFSTR("x")); |
would result in the string “abc”. A related function, CFStringTrimWhitespace
, does the same thing with whitespace characters, which include such characters as tabs and carriage returns.
Case operations
Three functions modify the case of a mutable string, making it all uppercase (CFStringUppercase
), all lowercase (CFStringLowercase
), or just the first character of each word in a string uppercase (CFStringCapitalize
).
Code Examples
Listing 1 exemplifies several of the functions that manipulate mutable CFString
objects:
Listing 1 Various operations on a mutable string
void mutableStringOperations() { |
CFMutableStringRef mstr; |
CFRange range; |
StringPtr pbuf; |
CFIndex length; |
mstr = CFStringCreateMutable(NULL, 0); |
CFStringAppend(mstr, CFSTR("Now is the time for all good men to come to the aid of their ")); |
CFStringAppend(mstr, CFSTR("party.")); |
CFShow(CFSTR("Mutable String 1 - Appended CFStrings")); |
CFShow(mstr); |
range = CFStringFind(mstr, CFSTR("good"), 0); |
if (range.length > 0) { |
CFStringReplace(mstr, range, CFSTR("bad")); |
CFShow(CFSTR("Mutable String 2 - Replaced substring")); |
CFShow(mstr); |
} |
CFStringUppercase(mstr, NULL); |
CFShow(CFSTR("Mutable String 3 - Convert to uppercase:")); |
CFShow(mstr); |
} |
When compiled and run, this code generates the following output:
Mutable String 1 - Appended CFStrings |
Now is the time for all good men to come to the aid of their party. |
Mutable String 2 - Replaced substring |
Now is the time for all bad men to come to the aid of their party. |
Mutable String 3 - Convert to uppercase: |
NOW IS THE TIME FOR ALL BAD MEN TO COME TO THE AID OF THEIR PARTY. |
Copyright © 2003, 2014 Apple Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2014-02-11