很多的應用都需要用到手機的唯一標示，而且要求這個唯一標示不能因為應用app的卸載或者改變而變化。

在iOS7以前是可以通過Mac地址來實現這個功能的，但是iOS7(包含)以後是無法獲得Mac地址的；蘋果官方推薦使用UUID，但是每次隨著APP的卸載重裝，UUID會隨之發生變化，那該如何處理呢？

我們需要一個能在app卸載重裝後不會改變的值，而keyChain恰巧就可以做到。配合UUID就可以實現了！讓我們來分析下：

1.我們首先需要導入Security.frameWork（keychain依賴它），然後需要一個keychain管理器，一個uuid管理器，文件組成如下：

 

2.首先來看MyKeychainManager,其實就是對keychain的增、刪、改、查，類似於數據庫的處理。

先通過.h文件來開放下增、刪、改、查四個接口：

 

#import 

@interface MyKeyChainManager : NSObject

+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service;

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

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

+ (void)delete:(NSString *)service;
    
@end

 

.m文件實現接口，keychain的使用網上很多，直接貼代碼了：

 

#import MyKeyChainManager.h

@implementation MyKeyChainManager : NSObject 

+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service {
    return [NSMutableDictionary dictionaryWithObjectsAndKeys:
            (__bridge_transfer id)kSecClassGenericPassword,(__bridge_transfer id)kSecClass,
            service, (__bridge_transfer id)kSecAttrService,
            service, (__bridge_transfer id)kSecAttrAccount,
            (__bridge_transfer id)kSecAttrAccessibleAfterFirstUnlock,(__bridge_transfer 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_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);
}

+ (id)load:(NSString *)service {
    id ret = nil;
    NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
    //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: %@, service, e);
        } @finally {
        }
    }
    return ret;
}

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

@end

3.再來看下MyUUIDManager文件，實現的是對UUID的增、刪、改、查，其中save既是贈也是改：

 

 

#import 

@interface MyUUIDManager: NSObject

+(void)saveUUID:(NSString *)uuid;

+(NSString *)getUUID;

+(void)deleteUUID;

@end

.m文件來實現它：

 

 

#import MyUUIDManager.h
#import MyKeyChainManager.h

@implementation MyUUIDManager

static NSString * const KEY_IN_KEYCHAIN = @com.myuuid.uuid;


+(void)saveUUID:(NSString *)uuid{
    if (uuid && uuid.length > 0) {
        [MyKeyChainManager save:KEY_IN_KEYCHAIN data:uuid];
    }
}


+(NSString *)getUUID{
    //先獲取keychain裡面的UUID字段，看是否存在
    NSString *uuid = (NSString *)[MyKeyChainManager load:KEY_IN_KEYCHAIN];
    
    //如果不存在則為首次獲取UUID，所以獲取保存。
    if (!uuid || uuid.length == 0) {
        CFUUIDRef puuid = CFUUIDCreate( nil );
        
        CFStringRef uuidString = CFUUIDCreateString( nil, puuid );
        
        uuid = [NSString stringWithFormat:@%@, uuidString];
        
        [self saveUUID:uuid];
        
        CFRelease(puuid);
        
        CFRelease(uuidString);
    }
    
    return uuid;
}



+(void)deleteUUID{
    [MyKeyChainManager delete:KEY_IN_KEYCHAIN];
}


@end

4.測試一下：

 

 

    NSString *uuid = [MyUUIDManager getUUID];
    NSLog(@uuid: %@,uuid);

2015-08-10 18:14:07.641 MyTest[3190:220331] uuid: 839E055B-09A5-42E1-A46C-DF4481E23333

5.把app刪除掉重新安裝一下，再打印一下：

 

 

2015-08-10 18:22:37.122 MyTest[3214:222053] uuid: 839E055B-09A5-42E1-A46C-DF4481E23333

結果是一樣的，搞定！稍後再發下swift版本的。