UIDevice+deviceToken+UUID (iOS < 6)

KMDevice.h

#import <Foundation/Foundation.h>

@interface KMDevice : NSObject

@property (nonatomic, readonly) NSString *uuid;
@property (nonatomic, readonly) NSString *deviceToken;

+ (KMDevice *)sharedDevice;

- (void)registerDeviceToken:(NSData *)devToken;

@end

KMDevice.m

#import "KMDevice.h"
#import "STKeychain.h"

#define APP_RELEASE_SAFELY(__POINTER) { [__POINTER release]; __POINTER = nil; }

static NSString * const UIApplication_UUID_Key = @"UniversallyUniqueIdentifier";

@interface KMDevice ()
- (NSString *)generateUUID;
- (void)loadUUIDFromKeychain;
- (void)saveUUIDToKeychain:(NSString *)uuid;
@end


@implementation KMDevice

@synthesize uuid = _uuid;

+ (KMDevice *)sharedDevice
{
    static KMDevice *_instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        _instance = [[self alloc] init];
        [_instance loadUUIDFromKeychain];
    });
    return _instance;
}

- (void)dealloc
{
    APP_RELEASE_SAFELY(_uuid);
    APP_RELEASE_SAFELY(_deviceToken);
    [super dealloc];
}

- (void)registerDeviceToken:(NSData *)devToken
{
    if (_deviceToken) {
        APP_RELEASE_SAFELY(_deviceToken);
    }
    NSString *deviceToken = [[[[devToken description]
                               stringByReplacingOccurrencesOfString:@"<" withString:@""]
                              stringByReplacingOccurrencesOfString:@">" withString:@""]
                             stringByReplacingOccurrencesOfString:@" " withString: @""];
    NSLog(@"deviceToken: %@", deviceToken);
    _deviceToken = [deviceToken copy];
}

- (NSString *)uuid
{
    if (_uuid && [_uuid length]) return _uuid;
    if (_uuid) APP_RELEASE_SAFELY(_uuid);

    NSString *gUUID = [self generateUUID];
    [self saveUUIDToKeychain:gUUID];
    _uuid = [gUUID copy];
    return _uuid;
}

- (NSString *)generateUUID
{
	// Create universally unique identifier (object)
	CFUUIDRef uuidObject = CFUUIDCreate(kCFAllocatorDefault);

	// Get the string representation of CFUUID object.
	// NSString *uuidStr = [(NSString *)CFUUIDCreateString(kCFAllocatorDefault, uuidObject) autorelease];
	CFStringRef uuidString = CFUUIDCreateString( kCFAllocatorDefault, uuidObject );
	NSString *uuidStr = (NSString *)CFStringCreateCopy( NULL, uuidString);

	// If needed, here is how to get a representation in bytes, returned as a structure
	// typedef struct {
	//   UInt8 byte0;
	//   UInt8 byte1;
	//   ...
	//   UInt8 byte15;
	// } CFUUIDBytes;
	// CFUUIDBytes bytes = CFUUIDGetUUIDBytes(uuidObject);

	CFRelease(uuidObject);
	CFRelease(uuidString);

    return [uuidStr autorelease];
}

- (void)loadUUIDFromKeychain
{
    NSError *error;

    NSString *identifier = [NSBundle mainBundle].bundleIdentifier;
    NSString *uuid = [STKeychain getPasswordForUsername:UIApplication_UUID_Key andServiceName:identifier error:&error];
    if ([uuid length]) {
        _uuid = [uuid copy];
    }
}

- (void)saveUUIDToKeychain:(NSString *)uuid
{
    NSError *error;

    NSString *identifier = [NSBundle mainBundle].bundleIdentifier;
    [STKeychain storeUsername:UIApplication_UUID_Key andPassword:uuid forServiceName:identifier updateExisting:YES error:&error];
}

@end