将数据保存在系统钥匙串里，即使应用被删除，数据还会被保存

@interface SaveObject : NSObject

// 保存数据

+ (void)save:(NSString *)key data:(id)data;

// 加载数据

+ (id)load:(NSString *)key;

// 删除数据

+ (void)delete:(NSString *)key;

@end

@implementation SaveObject

// 获取数据

+ (NSMutableDictionary *)keychainQuery:(NSString *)key

{

if (key) {

return [NSMutableDictionary dictionaryWithObjectsAndKeys:

(__bridge_transfer id)kSecClassGenericPassword, (__bridge_transfer id)kSecClass,

key, (__bridge_transfer id)kSecAttrService,

key, (__bridge_transfer id)kSecAttrAccount,

(__bridge_transfer id)kSecAttrAccessibleAfterFirstUnlock, (__bridge_transfer id)kSecAttrAccessible,

nil];

}

return nil;

}

// 保存数据

+ (void)save:(NSString *)key data:(id)data

{

if (key && data != nil) {

//Get search dictionary

NSMutableDictionary *keychainQuery = [self keychainQuery:key];

//Delete old item before add new item

SecItemDelete((__bridge_retained CFDictionaryRef)keychainQuery);

//Add new object to search dictionary(Attention:the data format)

[keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(__bridge_transfer id)kSecValueData];

//Add item to keychain with the search dictionary

SecItemAdd((__bridge_retained CFDictionaryRef)keychainQuery, NULL);

}

}

// 加载数据

+ (id)load:(NSString *)key

{

id ret = nil;

if (key) {

NSMutableDictionary *keychainQuery = [self keychainQuery:key];

//Configure the search setting

[keychainQuery setObject:(id)kCFBooleanTrue forKey:(__bridge_transfer id)kSecReturnData];

[keychainQuery setObject:(__bridge_transfer id)kSecMatchLimitOne forKey:(__bridge_transfer id)kSecMatchLimit];

CFDataRef keyData = NULL;

if (SecItemCopyMatching((__bridge_retained CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) {

@try {

ret = [NSKeyedUnarchiver unarchiveObjectWithData:(__bridge_transfer NSData *)keyData];

}

@catch (NSException *e) {

NSLog(@"Unarchive of %@ failed: %@", key, e);

}

@finally {}

}

}

return ret;

}

// 删除数据

+ (void)delete:(NSString *)key

{

NSMutableDictionary *keychainQuery = [self keychainQuery:key];

SecItemDelete((__bridge_retained CFDictionaryRef)keychainQuery);

}

@end