Testing file existence using NSURL

Question

Snow Leopard introduced many new methods to use NSURL objects to refer to files, not pathnames or Core Services\' FSRefs.

However, there\'s one task I can\'t find a

Answer 1

In Swift you can use the checkResourceIsReachable() method, which unfortunately will either return true (if the file is reachable) or throw an error (explaining why it cannot be reached).

To get a bool true/false value instead, use this syntax:

let exists = (try? inputFile.checkResourceIsReachable()) ?? false

If you'd like to log the error:

let exists: Bool
do {
  exists = try inputFile.checkResourceIsReachable()
} catch {
  exists = false
  print(error.localizedDescription)
}

Keep in mind this is an expensive operation and it could be out of date immediately after (if some other process is deleting a or unmounts a disk file while you're checking if it exists).

In general the preferred approach is not to check wether a file exists, instead simply attempt to read or write to a file and handle any error afterwards if it fails.