CFUUIDRef theUUID = CFUUIDCreate(NULL);
CFStringRef guid = CFUUIDCreateString(NULL, theUUID);
CFRelease(theUUID);
NSString *uuidString = [((NSString *)guid) stringByReplacingOccurrencesOfString:@"-" withString:@""];
CFRelease(guid);
为了能标识该字符串，所以一般使用一个固定的字符串来标志
- (NSString *)pathForTemporaryFileWithPrefix:(NSString *)prefix
{
NSString * result;
CFUUIDRef uuid;
CFStringRef uuidStr;
uuid = CFUUIDCreate(NULL);
assert(uuid != NULL);
uuidStr = CFUUIDCreateString(NULL, uuid);
assert(uuidStr != NULL);
result = [NSTemporaryDirectory()stringByAppendingPathComponent:[NSStringstringWithFormat:@"%@-%@", prefix, uuidStr]];
assert(result != nil);
CFRelease(uuidStr);
CFRelease(uuid);
return result;
}