NSFileManager unique file names

Question

I need a quick and easy way to store files with unique file names on iOS. I need to prefix the file with a string, and then append the generated unique identifier to the end. I was hoping NSFileManager had some convenient method to do this, but I can't seem to find it.

I was looking at createFileAtPath:contents:attributes:, but am unsure if the attributes will give me that unique file name.

Answer 1

Create your own file name:

CFUUIDRef uuid = CFUUIDCreate(NULL); CFStringRef uuidString = CFUUIDCreateString(NULL, uuid); CFRelease(uuid); NSString *uniqueFileName = [NSString stringWithFormat:@"%@%@", prefixString, (NSString *)uuidString]; CFRelease(uuidString); 

A simpler alternative proposed by @darrinm in the comments:

NSString *prefixString = @"MyFilename";  NSString *guid = [[NSProcessInfo processInfo] globallyUniqueString] ; NSString *uniqueFileName = [NSString stringWithFormat:@"%@_%@", prefixString, guid];  NSLog(@"uniqueFileName: '%@'", uniqueFileName); 

NSLog output:
uniqueFileName: 'MyFilename_680E77F2-20B8-444E-875B-11453B06606E-688-00000145B460AF51'

Note: iOS6 introduced the NSUUID class which can be used in place of CFUUID.

NSString *guid = [[NSUUID new] UUIDString]; 

Answer 2

I use current date to generate random file name with a given extension. This is one of the methods in my NSFileManager category:

 + (NSString*)generateFileNameWithExtension:(NSString *)extensionString {     // Extenstion string is like @".png"      NSDate *time = [NSDate date];     NSDateFormatter* df = [NSDateFormatter new];     [df setDateFormat:@"dd-MM-yyyy-hh-mm-ss"];     NSString *timeString = [df stringFromDate:time];     NSString *fileName = [NSString stringWithFormat:@"File-%@%@", timeString, extensionString];      return fileName; }