标签：dealloc atom lin imp src start elf int pen
NSUserDefaults可以存取一些短小的信息。
比如存入再读出一个字符串到NSUserDefaults：
- NSString *string = [NSString stringWithString @"hahaha"]; - NSUserDefaults *ud = [NSUserDefaults standardUserDefaults]; - [ud setObject:string forKey:@"myKey"]; - NSString *value; - value = [ud objectForKey:"myKey"];
但是并不是所有的东西都能往里放的。NSUserDefaults只支持： NSString, NSNumber, NSDate, NSArray, NSDictionary.
如果把一个自定义的类存到一个NSArray里，然后再存到NSUserDefaults里也是不能成功的。不信可以试试，如果你成功的请告诉我。
那怎么办呢？
我找到的方法是，让这个自定义类实现<NSCoding>协议中的- (id) initWithCoder: (NSCoder *)coder方法和- (void) encodeWithCoder: (NSCoder *)coder方法（obj-c的协议protocol就是java的接口interface，就是C++的纯虚函数），然后把该自定义的类对象编码到NSData中，再从NSUserDefaults中进行读取。
粘代码：
假设有这样一个简单的类对象
- @interface BusinessCard : NSObject <NSCoding>{ - NSString *_firstName; - NSString *_lastName; - } - @property (nonatomic, retain) NSString *_firstName; - @property (nonatomic, retain) NSString *_lastName; - @end; - - @implementation BusinessCard - @synthesize _firstName, _lastName; - - (void)dealloc{ - [_firstName release]; - [_lastName release]; - [super dealloc]; - } - - (id) initWithCoder: (NSCoder *)coder - { - if (self = [super init]) - { - self._firstName = [coder decodeObjectForKey:@"_firstName"]; - self._lastName = [coder decodeObjectForKey:@"_lastName"]; - } - return self; - } - - (void) encodeWithCoder: (NSCoder *)coder - { - [coder encodeObject:_firstName forKey:@"_firstName"]; - [coder encodeObject:_lastName forKey:@"_lastName"]; - - } - - @end
然后再存取时通过NSData做载体：
BusinessCard *bc = [[BusinessCard alloc] init]; NSUserDefaults *ud = [NSUserDefaults standardUserDefaults]; NSData *udObject = [NSKeyedArchiver archivedDataWithRootObject:bc]; [ud setObject:udObject forKey:@"myBusinessCard"]; [bc release]; udObject = nil; udObject = [ud objectForKey:@"myBusinessCard"]; bc = [NSKeyedUnarchiver unarchiveObjectWithData:udObject] ;
标签：dealloc atom lin imp src start elf int pen
原文地址：http://www.cnblogs.com/IT-jqm/p/NSUserDefaults.html
