我是用来标识唯一设备的，因为苹果不让用udid了，所以用的open udid的第三方一个类。
OpenUDID的类比较长就不在这里发了，需要的可以去网上下，实在搜不到可以找我要。
下面说下用keychain来存取。
参考网站：http://blog.csdn.net/sqq521/article/details/11988995。尊重原创。
我自己写的类如下：
头文件：
#import <Foundation/Foundation.h>
@interface Keychain : NSObject
+ (void)save:(NSString *)service data:(id)data;
+ (id)load:(NSString *)service;
//+ (void)delete:(NSString *)service;
@end
.m文件：
#import "Keychain.h"
@implementation Keychain
+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service {
return [NSMutableDictionary dictionaryWithObjectsAndKeys:
(id)kSecClassGenericPassword,(id)kSecClass,
service, (id)kSecAttrService,
service, (id)kSecAttrAccount,
(id)kSecAttrAccessibleAfterFirstUnlock,(id)kSecAttrAccessible,
nil];
}
+ (void)save:(NSString *)service data:(id)data {
//Get search dictionary
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
//Delete old item before add new item
SecItemDelete((CFDictionaryRef)keychainQuery);
//Add new object to search dictionary(Attention:the data format)
[keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(id)kSecValueData];
//Add item to keychain with the search dictionary
SecItemAdd((CFDictionaryRef)keychainQuery, NULL);
}
+ (id)load:(NSString *)service {
id ret = nil;
NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
//Configure the search setting
//Since in our simple case we are expecting only a single attribute to be returned (the password) we can set the attribute kSecReturnData to kCFBooleanTrue
[keychainQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];
[keychainQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];
CFDataRef keyData = NULL;
if (SecItemCopyMatching((CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) {
@try {
ret = [NSKeyedUnarchiver unarchiveObjectWithData:(NSData *)keyData];
} @catch (NSException *e) {
NSLog(@"Unarchive of %@ failed: %@", service, e);
} @finally {
}
}
if (keyData)
CFRelease(keyData);
return ret;
}
@end
具体调用如下：
NSString * const KEY_UDID = @"uuid4Pet";
NSString * uuid = [Keychain load:KEY_UDID];
NSLog(@"%@", uuid);
if (uuid == nil || uuid.length == 0) {
[Keychain save:KEY_UDID data:[OpenUDID value]];
}
NSLog(@"%@", [Keychain load:KEY_UDID]);
[USER setObject:[Keychain load:KEY_UDID] forKey:@"UDID"];
USER是我定义的宏，里面是NSUserDefaults。