pathExtension is unavailable: Use pathExtension on NSURL instead. Swift 2.0

Or you can use this extension:

extension String {    var ns: NSString {        return self as NSString    }    var pathExtension: String {        return ns.pathExtension    }    var lastPathComponent: String {        return ns.lastPathComponent    }}

Base on this link, this extension will help you in many case.

extension String {    var lastPathComponent: String {        get {            return (self as NSString).lastPathComponent        }    }    var pathExtension: String {        get {            return (self as NSString).pathExtension        }    }    var stringByDeletingLastPathComponent: String {        get {            return (self as NSString).stringByDeletingLastPathComponent        }    }    var stringByDeletingPathExtension: String {        get {            return (self as NSString).stringByDeletingPathExtension        }    }    var pathComponents: [String] {        get {            return (self as NSString).pathComponents        }    }    func stringByAppendingPathComponent(path: String) -> String {        let nsSt = self as NSString        return nsSt.stringByAppendingPathComponent(path)    }    func stringByAppendingPathExtension(ext: String) -> String? {        let nsSt = self as NSString        return nsSt.stringByAppendingPathExtension(ext)    }}

Xcode 8.3.2 • Swift 3.1

extension String {    var fileURL: URL {        return URL(fileURLWithPath: self)    }    var pathExtension: String {        return fileURL.pathExtension    }    var lastPathComponent: String {        return fileURL.lastPathComponent    }}