iOS 基础类解析 - NSCharacterSet

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NSCharacterSet Class Reference

Inherits from	NSObject
Conforms to	NSCoding NSCopying NSMutableCopying NSObject (NSObject)
Framework	/System/Library/Frameworks/Foundation.framework
Availability	Available in iOS 2.0 and later.
Companion guide	String Programming Guide
Declared in	NSCharacterSet.h NSURL.h
Related sample code	Advanced UISearchBar KMLViewer MVCNetworking SimpleURLConnections Using NSXMLParser to parse XML documents

Overview

An NSCharacterSet object represents a set of Unicode-compliant characters. NSString and NSScanner objects
use NSCharacterSet objects to group characters together for searching operations, so that they can find any of a particular set of characters during a search. The cluster’s
two public classes, NSCharacterSet andNSMutableCharacterSet, declare the programmatic interface
for static and dynamic character sets, respectively.

The objects you create using these classes are referred to as character set objects (and when no confusion will result, merely as character sets). Because of the nature of class clusters, character set objects
aren’t actual instances of the NSCharacterSet or NSMutableCharacterSet classes but of one
of their private subclasses. Although a character set object’s class is private, its interface is public, as declared by these abstract superclasses, NSCharacterSet and NSMutableCharacterSet.
The character set classes adopt the NSCopying and NSMutableCopying protocols, making it
convenient to convert a character set of one type to the other.

The NSCharacterSet class declares the programmatic interface for an object that manages a set of Unicode characters (see the NSString class
cluster specification for information on Unicode). NSCharacterSet’s principal primitive method, characterIsMember:,
provides the basis for all other instance methods in its interface. A subclass of NSCharacterSet needs only to implement this method, plus mutableCopyWithZone:,
for proper behavior. For optimal performance, a subclass should also override bitmapRepresentation,
which otherwise works by invoking characterIsMember: for
every possible Unicode value.

NSCharacterSet is “toll-free bridged” with its Core Foundation counterpart, CFCharacterSetRef.
See “Toll-Free
Bridging” for more information on toll-free bridging.

The mutable subclass of NSCharacterSet is NSMutableCharacterSet.