[iOS Keychain本地长期键值存储]

目前本地存储方式大致有：Sqlite,Coredata,NSUserdefaults。但他们都是在删除APP后就会被删除，如果长期使用存储，可以使用Keychain钥匙串来实现。

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:
            (__bridge id)kSecClassGenericPassword,(__bridge id)kSecClass,
            service, (__bridge id)kSecAttrService,
            service, (__bridge id)kSecAttrAccount,
            (__bridge id)kSecAttrAccessibleAfterFirstUnlock,(__bridge 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((__bridge CFDictionaryRef)keychainQuery);
    //Add new object to search dictionary(Attention:the data format)
    [keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(__bridge id)kSecValueData];
    //Add item to keychain with the search dictionary
    SecItemAdd((__bridge 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:(__bridge id)kSecReturnData];
    [keychainQuery setObject:(__bridge id)kSecMatchLimitOne forKey:(__bridge id)kSecMatchLimit];
    CFDataRef keyData = NULL;
    if (SecItemCopyMatching((__bridge CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) {
        @try {
            ret = [NSKeyedUnarchiver unarchiveObjectWithData:(__bridge 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((__bridge CFDictionaryRef)keychainQuery);
}
@end

调用：（以生成UUID为例）

#define UUIDKEY @"UUID"
#pragma mark--获取设备UUID
-(NSString*)uuid{
    if ([CHKeychain load:UUIDKEY]) {
        NSString *result = [CHKeychain load:UUIDKEY];
        _PhoneUUID=result;
        NSLog(@"已存在手机UUID：%@",result);
        return result;
    }
    else
    {
        CFUUIDRef puuid = CFUUIDCreate( nil );
        CFStringRef uuidString = CFUUIDCreateString( nil, puuid );
        NSString * result = (NSString *)CFBridgingRelease(CFStringCreateCopy( NULL, uuidString));
        CFRelease(puuid);
        CFRelease(uuidString);
        [CHKeychain save:UUIDKEY data:result];
        NSLog(@"初次创建手机UUID：%@",result);
        _PhoneUUID=result;
        return result;
    }
    return nil;
}

以前貌似一定要通过自己新建Plist文件配置开发者账号来实现，现在好像已经有接口了，比较简单。

GITHUB:https://github.com/rayshen/ShenUUIDDemo