给你一个小技巧:

/**
 @method uniqueDeviceIdentifier
 @abstract A unique device identifier is a hash value composed from various hardware identifiers such
 as the device’s serial number. It is guaranteed to be unique for every device but cannot 
 be tied to a user account. [UIDevice Class Reference]
 @return An 1-way hashed identifier unique to this device.
 */
+ (NSString *)uniqueDeviceIdentifier {      
    NSString *systemId = nil;
    // We collect it as long as it is available along with a randomly generated ID.
    // This way, when this becomes unavailable we can map existing users so the
    // new vs returning counts do not break.
    if (([[[UIDevice currentDevice] systemVersion] floatValue] < 6.0f)) {
        SEL udidSelector = NSSelectorFromString(@"uniqueIdentifier");
        if ([[UIDevice currentDevice] respondsToSelector:udidSelector]) {
            systemId = [[UIDevice currentDevice] performSelector:udidSelector];
        }
    }
    else {
        systemId = [NSUUID UUID];
    }
    return systemId;
}

使用上面提到的SSKeychain和代码。下面是复制/粘贴(添加SSKeychain模块)的代码:

+(NSString *) getUUID {

//Use the bundle name as the App identifier. No need to get the localized version.

NSString *Appname = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleName"];    

//Check if we have UUID already

NSString *retrieveuuid = [SSKeychain passwordForService:Appname account:@"user"];

if (retrieveuuid == NULL)
{

    //Create new key for this app/device

    CFUUIDRef newUniqueId = CFUUIDCreate(kCFAllocatorDefault);

    retrieveuuid = (__bridge_transfer NSString*)CFUUIDCreateString(kCFAllocatorDefault, newUniqueId);

    CFRelease(newUniqueId);

    //Save key to Keychain
    [SSKeychain setPassword:retrieveuuid forService:Appname account:@"user"];
}

return retrieveuuid;

}

获得UDID的有效方法:

Launch a web server inside the app with two pages: one should return specially crafted MobileConfiguration profile and another should collect UDID. More info here, here and here. You open the first page in Mobile Safari from inside the app and it redirects you to Settings.app asking to install configuration profile. After you install the profile, UDID is sent to the second web page and you can access it from inside the app. (Settings.app has all necessary entitlements and different sandbox rules).

一个使用RoutingHTTPServer的例子:

import UIKit
import RoutingHTTPServer

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var bgTask = UIBackgroundTaskInvalid
    let server = HTTPServer()

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        application.openURL(NSURL(string: "http://localhost:55555")!)
        return true
    }

    func applicationDidEnterBackground(application: UIApplication) {
        bgTask = application.beginBackgroundTaskWithExpirationHandler() {
            dispatch_async(dispatch_get_main_queue()) {[unowned self] in
                application.endBackgroundTask(self.bgTask)
                self.bgTask = UIBackgroundTaskInvalid
            }
        }
    }
}

class HTTPServer: RoutingHTTPServer {
    override init() {
        super.init()
        setPort(55555)
        handleMethod("GET", withPath: "/") {
            $1.setHeader("Content-Type", value: "application/x-apple-aspen-config")
            $1.respondWithData(NSData(contentsOfFile: NSBundle.mainBundle().pathForResource("udid", ofType: "mobileconfig")!)!)
        }
        handleMethod("POST", withPath: "/") {
            let raw = NSString(data:$0.body(), encoding:NSISOLatin1StringEncoding) as! String
            let plistString = raw.substringWithRange(Range(start: raw.rangeOfString("<?xml")!.startIndex,end: raw.rangeOfString("</plist>")!.endIndex))
            let plist = NSPropertyListSerialization.propertyListWithData(plistString.dataUsingEncoding(NSISOLatin1StringEncoding)!, options: .allZeros, format: nil, error: nil) as! [String:String]

            let udid = plist["UDID"]! 
            println(udid) // Here is your UDID!

            $1.statusCode = 200
            $1.respondWithString("see https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/iPhoneOTAConfiguration/ConfigurationProfileExamples/ConfigurationProfileExamples.html")
        }
        start(nil)
    }
}

下面是udid.mobileconfig的内容:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
    <dict>
        <key>PayloadContent</key>
        <dict>
            <key>URL</key>
            <string>http://localhost:55555</string>
            <key>DeviceAttributes</key>
            <array>
                <string>IMEI</string>
                <string>UDID</string>
                <string>PRODUCT</string>
                <string>VERSION</string>
                <string>SERIAL</string>
            </array>
        </dict>
        <key>PayloadOrganization</key>
        <string>udid</string>
        <key>PayloadDisplayName</key>
        <string>Get Your UDID</string>
        <key>PayloadVersion</key>
        <integer>1</integer>
        <key>PayloadUUID</key>
        <string>9CF421B3-9853-9999-BC8A-982CBD3C907C</string>
        <key>PayloadIdentifier</key>
        <string>udid</string>
        <key>PayloadDescription</key>
        <string>Install this temporary profile to find and display your current device's UDID. It is automatically removed from device right after you get your UDID.</string>
        <key>PayloadType</key>
        <string>Profile Service</string>
    </dict>
</plist>

配置文件安装将失败(我没有费心实现预期的响应，请参阅文档)，但应用程序将获得正确的UDID。你还应该在mobileconfig上签名。

+ (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;
}

给你一个小技巧:

/**
 @method uniqueDeviceIdentifier
 @abstract A unique device identifier is a hash value composed from various hardware identifiers such
 as the device’s serial number. It is guaranteed to be unique for every device but cannot 
 be tied to a user account. [UIDevice Class Reference]
 @return An 1-way hashed identifier unique to this device.
 */
+ (NSString *)uniqueDeviceIdentifier {      
    NSString *systemId = nil;
    // We collect it as long as it is available along with a randomly generated ID.
    // This way, when this becomes unavailable we can map existing users so the
    // new vs returning counts do not break.
    if (([[[UIDevice currentDevice] systemVersion] floatValue] < 6.0f)) {
        SEL udidSelector = NSSelectorFromString(@"uniqueIdentifier");
        if ([[UIDevice currentDevice] respondsToSelector:udidSelector]) {
            systemId = [[UIDevice currentDevice] performSelector:udidSelector];
        }
    }
    else {
        systemId = [NSUUID UUID];
    }
    return systemId;
}

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。