Let’s see some useful method about NSURL

Return the name of a file (with or without extension) from NSURLRequest:

- (NSString *)getFilenameFromRequest:(NSURLRequest *)request avoidExtension:(BOOL)avoidExtension 
{
  NSString *filePath = [[[request URL] path] lastPathComponent];
    if (avoidExtension) {
      NSArray *a = [filePath componentsSeparatedByString:@"."];
      return [a objectAtIndex:0];
    }
  return filePath;
}

Return the file extension from NSURLRequest:

- (NSString *)getExtensionFromRequest:(NSURLRequest *)request 
{
  NSString *filePath = [[[request URL] path] lastPathComponent];
  NSArray *a = [filePath componentsSeparatedByString:@"."];
  return [a objectAtIndex:1];
}

Finally, How to convert an address from NSString to NSURL and vice versa:

// filename
NSString *filePath = @"/path/filetext.txt";

// NSString to NSURL
NSURL *fileURL = [[NSURL alloc] initFileURLWithPath: filePath]; // do release

// or
NSURL fileURL = [NSURL fileURLWithPath: filePath]; // autorelease

// NSURL to NSString
NSString *filePath = [fileUrl absoluteString];