CFMutableString manages dynamic strings. The basic interface for managing strings is provided by CFString. CFMutableString adds functions to modify the contents of a string.
CFMutableString is “toll-free bridged” with its Cocoa Foundation counterpart,
NSMutable. This means that the Core Foundation type is interchangeable in function or method calls with the bridged Foundation object. Therefore, in a method where you see an
NSMutable parameter, you can pass in a
CFMutable, and in a function where you see a
CFMutable parameter, you can pass in an NSMutableString instance. This also applies to concrete subclasses of NSMutableString. See Toll-Free Bridged Types for more information on toll-free bridging.