我们可以在ios7中使用identifierForVendor，

-(NSString*)uniqueIDForDevice
{
    NSString* uniqueIdentifier = nil;
    if( [UIDevice instancesRespondToSelector:@selector(identifierForVendor)] ) { // >=iOS 7
        uniqueIdentifier = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
    } else { //<=iOS6, Use UDID of Device       
            CFUUIDRef uuid = CFUUIDCreate(NULL);
            //uniqueIdentifier = ( NSString*)CFUUIDCreateString(NULL, uuid);- for non- ARC
            uniqueIdentifier = ( NSString*)CFBridgingRelease(CFUUIDCreateString(NULL, uuid));// for ARC
            CFRelease(uuid);
         }
    }
return uniqueIdentifier;
}

——重要提示——

UDID和identifierForVendor是不同的:——

1.) On uninstalling  and reinstalling the app identifierForVendor will change.

2.) The value of identifierForVendor remains the same for all the apps installed from the same vendor on the device.

3.) The value of identifierForVendor also changes for all the apps if any of the app (from same vendor) is reinstalled.

iOS 11引入了DeviceCheck框架。它有一个完整的解决方案，唯一地识别设备。

如果有人在寻找替代方案时偶然发现了这个问题。我在IDManager课上就采用了这种方法， 这是不同解的集合。KeyChainUtil是一个从keychain读取的包装器。 您还可以使用散列MAC地址作为一种唯一ID。

/*  Apple confirmed this bug in their system in response to a Technical Support Incident 
    request. They said that identifierForVendor and advertisingIdentifier sometimes 
    returning all zeros can be seen both in development builds and apps downloaded over the 
    air from the App Store. They have no work around and can't say when the problem will be fixed. */
#define kBuggyASIID             @"00000000-0000-0000-0000-000000000000"

+ (NSString *) getUniqueID {
    if (NSClassFromString(@"ASIdentifierManager")) {
        NSString * asiID = [[[ASIdentifierManager sharedManager] advertisingIdentifier] UUIDString];
        if ([asiID compare:kBuggyASIID] == NSOrderedSame) {
            NSLog(@"Error: This device return buggy advertisingIdentifier.");
            return [IDManager getUniqueUUID];
        } else {
            return asiID;
        }

    } else {
        return [IDManager getUniqueUUID];
    }
}


+ (NSString *) getUniqueUUID {
    NSError * error;
    NSString * uuid = [KeychainUtils getPasswordForUsername:kBuyassUser andServiceName:kIdOgBetilngService error:&error];
    if (error) {
        NSLog(@"Error geting unique UUID for this device! %@", [error localizedDescription]);
        return nil;
    }
    if (!uuid) {
        DLog(@"No UUID found. Creating a new one.");
        uuid = [IDManager GetUUID];
        uuid = [Util md5String:uuid];
        [KeychainUtils storeUsername:USER_NAME andPassword:uuid forServiceName:SERVICE_NAME updateExisting:YES error:&error];
        if (error) {
            NSLog(@"Error getting unique UUID for this device! %@", [error localizedDescription]);
            return nil;
        }
    }
    return uuid;
}

/* NSUUID is after iOS 6. */
+ (NSString *)GetUUID
{
    CFUUIDRef theUUID = CFUUIDCreate(NULL);
    CFStringRef string = CFUUIDCreateString(NULL, theUUID);
    CFRelease(theUUID);
    return [(NSString *)string autorelease];
}

#pragma mark - MAC address
// Return the local MAC addy
// Courtesy of FreeBSD hackers email list
// Last fallback for unique identifier
+ (NSString *) getMACAddress
{
    int                 mib[6];
    size_t              len;
    char                *buf;
    unsigned char       *ptr;
    struct if_msghdr    *ifm;
    struct sockaddr_dl  *sdl;

    mib[0] = CTL_NET;
    mib[1] = AF_ROUTE;
    mib[2] = 0;
    mib[3] = AF_LINK;
    mib[4] = NET_RT_IFLIST;

    if ((mib[5] = if_nametoindex("en0")) == 0) {
        printf("Error: if_nametoindex error\n");
        return NULL;
    }

    if (sysctl(mib, 6, NULL, &len, NULL, 0) < 0) {
        printf("Error: sysctl, take 1\n");
        return NULL;
    }

    if ((buf = malloc(len)) == NULL) {
        printf("Error: Memory allocation error\n");
        return NULL;
    }

    if (sysctl(mib, 6, buf, &len, NULL, 0) < 0) {
        printf("Error: sysctl, take 2\n");
        free(buf); // Thanks, Remy "Psy" Demerest
        return NULL;
    }

    ifm = (struct if_msghdr *)buf;
    sdl = (struct sockaddr_dl *)(ifm + 1);
    ptr = (unsigned char *)LLADDR(sdl);
    NSString *outstring = [NSString stringWithFormat:@"%02X:%02X:%02X:%02X:%02X:%02X", *ptr, *(ptr+1), *(ptr+2), *(ptr+3), *(ptr+4), *(ptr+5)];

    free(buf);
    return outstring;
}

+ (NSString *) getHashedMACAddress
{
    NSString * mac = [IDManager getMACAddress];
    return [Util md5String:mac];
}

+ (NSString *)md5String:(NSString *)plainText
{
    if(plainText == nil || [plainText length] == 0)
        return nil;

    const char *value = [plainText UTF8String];
    unsigned char outputBuffer[CC_MD5_DIGEST_LENGTH];
    CC_MD5(value, strlen(value), outputBuffer);

    NSMutableString *outputString = [[NSMutableString alloc] initWithCapacity:CC_MD5_DIGEST_LENGTH * 2];
    for(NSInteger count = 0; count < CC_MD5_DIGEST_LENGTH; count++){
        [outputString appendFormat:@"%02x",outputBuffer[count]];
    }
    NSString * retString = [NSString stringWithString:outputString];
    [outputString release];
    return retString;
}

我相信苹果公司的这一变化惹恼了很多人。我开发了一个iOS的簿记应用程序，并有一个在线服务来同步不同设备上的更改。该服务维护所有设备的数据库以及需要传播到这些设备的更改。因此，了解哪种设备是哪种设备很重要。我使用UIDevice uniqueIdentifier跟踪设备，为了它的价值，这里是我的想法。

Generate a UUID and store in user defaults? No good because this does not persist when the user deletes the app. If they install again later the online service should not create a new device record, that would waste resources on the server and give a list of devices containing the same one two or more times. Users would see more than one "Bob's iPhone" listed if they re-installed the app. Generate a UUID and store in the keychain? This was my plan, since it persists even when the app is uninstalled. But when restoring an iTunes backup to a new iOS device, the keychain is transferred if the backup is encrypted. This could lead to two devices containing the same device id if the old and new devices are both in service. These should be listed as two devices in the online service, even if the device name is the same. Generate a hash the MAC address and bundle id? This looks like the best solution for what I need. By hashing with the bundle id, the generated device id is not going to enable the device to be tracked across apps and I get a unique ID for the app+device combination.

有趣的是，苹果自己的文档提到通过计算系统Mac地址加上bundle id和版本的哈希来验证Mac App Store收据。所以这似乎是政策允许的，但是否通过应用审查我还不知道。

iOS 6中引入的UIDevice identifierForVendor可以满足你的需求。

identifierForVendor是一个字母数字字符串，用于唯一标识应用程序供应商的设备。(只读)

@property(nonatomic, readonly, retain) NSUUID *identifierForVendor

对于运行在同一设备上的来自同一供应商的应用程序，此属性的值是相同的。对于同一设备上来自不同供应商的应用程序返回不同的值，对于不同设备上的应用程序返回不同的值，与供应商无关。

在iOS 6.0及更高版本中可用，在UIDevice.h中声明

对于iOS 5，请参考此链接UIDevice-with-UniqueIdentifier-for-iOS-5

下面的代码有助于获得UDID:

        udid = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
        NSLog(@"UDID : %@", udid);