iOS UUID配合keychain的替换方案实现 - Herooic

参考：http://blog.youkuaiyun.com/u011439689/article/details/18707387

iOS的keychain服务提供了一种安全的保存私密信息（密码，序列号，证书等）的方式，每个iOS程序都有一个独立的keychain存储。相对于NSUserDefaults、文件保存等一般方式，keychain保存更为安全，而且keychain里保存的信息不会因App被删除而丢失，所以在重装App后，keychain里的数据还能使用。

在应用里使用使用keyChain，我们需要导入Security.framework

要先声明公共区的名称，官方文档管这个名称叫“keychain access group”，声明的方法是新建一个plist文件，名字随便起，内容如下： 

“yourAppID.com.yourCompany.whatever”就是你要起的公共区名称

获取UUID 并保存到keychain中：

#pragma mark--获取设备UUID
-(NSString*) uuid {
   
  if ([CHKeychain load:UUIDKEY]) {
    
     NSString *result = [CHKeychain load:UUIDKEY];
    
    return result;
  }
  else
  {
    CFUUIDRef puuid = CFUUIDCreate( nil );
    CFStringRef uuidString = CFUUIDCreateString( nil, puuid );
    NSString * result = (NSString *)CFStringCreateCopy( NULL, uuidString);
    CFRelease(puuid);
    CFRelease(uuidString);
    
    [CHKeychain save:UUIDKEY data:result];
    
    return [result autorelease];
  }
  
 
  return nil;
}

CHKeychain 的实现代码（需要导入Security.framework）：

CHKeychain.h

#import <Foundation/Foundation.h>

@interface CHKeychain : NSObject

+ (void)save:(NSString *)service data:(id)data;
+ (id)load:(NSString *)service;
+ (void)deleteData:(NSString *)service;


@end

CHKeychain.m

#import "CHKeychain.h"

@implementation CHKeychain
+ (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;
}

+ (void)delete:(NSString *)service {
  NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
  SecItemDelete((CFDictionaryRef)keychainQuery);
}

@end