IOS 中NSUserDefaults读取和写入自定义对象的实现方法

NSString *string = [NSString stringWithString @"hahaha"]; 
NSUserDefaults *ud = [NSUserDefaults standardUserDefaults]; 
[ud setObject:string forKey:@"myKey"]; 
NSString *value; 
value = [ud objectForKey:"myKey"]; 
 

@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 

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] ;