ios - Preventing Overwrite When Calling writeToFile: -

i'm trying save image disk every time save button pressed. code i'm using:

nsarray* documentdirectories = nssearchpathfordirectoriesindomains(nsdocumentdirectory, nsuserdomainmask,yes);  nsstring* documentdirectory = [documentdirectories objectatindex:0]; nsstring* documentdirectoryfilename = [documentdirectory stringbyappendingpathcomponent:@"piclogs"];  [pdfdata writetofile:documentdirectoryfilename atomically:yes]; 

now, file saved overwrite saved file every time method called. i'm trying find way store every picture taken in there, rather have overwritten every time. know if there simple solution achieve this? browsed through docs couldn't find relevant.

use nsuuid or cfuuidcreate create unique name can use file.