It is always different. UUID includes timestamps, so every time you call this function, you will get a different (random) one.
I have followed this approach in IDManager
class,
This is a collection from different solutions. KeyChainUtil is a wrapper to read from keychain. A similar keychain util is found in github.
// IDManager.m
/*
A replacement for deprecated uniqueIdentifier API. Apple restrict using this from 1st May, 2013.
We have to consider,
* iOS <6 have not the ASIIdentifer API
* When the user upgrade from iOS < 6 to >6
- Check if there is a UUID already stored in keychain. Then use that.
- In that case, this UUID is constant for whole device lifetime. Keychain item is not deleted with application deletion.
*/
#import "IDManager.h"
#import "KeychainUtils.h"
#import "CommonUtil.h"
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 60000
#import <AdSupport/AdSupport.h>
#endif
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <net/if.h>
#include <net/if_dl.h>
/* 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"
#pragma mark
#pragma mark
@implementation IDManager
+ (NSString *) getUniqueID {
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 60000
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 {
#endif
return [IDManager getUniqueUUID];
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 60000
}
#endif
}
+ (NSString *) getUniqueUUID
{
NSError * error;
NSString * uuid = [KeychainUtils getPasswordForUsername:@"UserName" andServiceName:@"YourServiceName" 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 = [CommonUtil md5String:uuid]; // create md5 hash for security reason
[KeychainUtils storeUsername:@"UserName" andPassword:uuid forServiceName:@"YourServiceName" updateExisting:YES error:&error];
if (error) {
NSLog(@"Error geting unique UUID for this device! %@", [error localizedDescription]);
return nil;
}
}
return uuid;
}
+ (NSString *) readUUIDFromKeyChain {
NSError * error;
NSString * uuid = [KeychainUtils getPasswordForUsername:@"UserName" andServiceName:@"YourServiceName" error:&error];
if (error) {
NSLog(@"Error geting unique UUID for this device! %@", [error localizedDescription]);
return nil;
}
return uuid;
}
/* NSUUID is after iOS 6. So we are using CFUUID for compatibility with iOS 4.3 */
+ (NSString *)getUUID
{
CFUUIDRef theUUID = CFUUIDCreate(NULL);
CFStringRef string = CFUUIDCreateString(NULL, theUUID);
CFRelease(theUUID);
return [(NSString *)string autorelease];
}
#pragma mark - MAC address
/* THIS WILL NOT WORK IN iOS 7. IT WILL RETURN A CONSTANT MAC ADDRESS ALL THE TIME.
SEE - https://developer.apple.com/news/?id=8222013a
*/
// Return the local MAC address
// 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 [CommonUtil md5String:mac];
}
@end