How to generate a unique identifier?

Question

I need to generate some int value that would never repeat (at least theoretically). I know there is arc4random() fnc but I'm not sure how to use it with some current date or smth :(

Answer 1

This returns a unique key very similar to UUID generated in MySQL.

+ (NSString *)uuid {     CFUUIDRef uuidRef = CFUUIDCreate(NULL);     CFStringRef uuidStringRef = CFUUIDCreateString(NULL, uuidRef);     CFRelease(uuidRef);     return [(NSString *)uuidStringRef autorelease]; } 

ARC version:

+ (NSString *)uuid {     CFUUIDRef uuidRef = CFUUIDCreate(NULL);     CFStringRef uuidStringRef = CFUUIDCreateString(NULL, uuidRef);     CFRelease(uuidRef);     return (__bridge_transfer NSString *)uuidStringRef; } 

Answer 2

A simple version to generate UUID (iOS 6 or later).

Objective-C:

NSString *UUID = [[NSUUID UUID] UUIDString]; 

Swift 3+:

let uuid = UUID().uuidString 

It will generate something like 68753A44-4D6F-1226-9C60-0050E4C00067, which is unique every time you call this function, even across multiple devices and locations.

Reference: https://developer.apple.com/library/ios/documentation/Foundation/Reference/NSUUID_Class/Reference/Reference.html