Updated from Swift 1 to Swift 2 - xcode

Question

I wrote this code in the previous version of Swift and Xcode and now when I updated xcode to 7.0.1 and updated swift to another version I got a lot of errors. This is something I can't solve and it would be so nice if you could help me. The fat text is the error. The part from >>> to <<< is the part that I need help with so the > and < is not in the real code.
extension SKNode {
class func unarchiveFromFile(file : String) -> SKNode? {
if let path = NSBundle.mainBundle().pathForResource(file, ofType: "sks") {
>>> var sceneData = NSData(contentsOfFile: path, options: .DataReadingMappedIfSafe, error: nil)! <<<
var archiver = NSKeyedUnarchiver(forReadingWithData: sceneData)
archiver.setClass(self.classForKeyedUnarchiver(), forClassName: "SKScene")
let scene = archiver.decodeObjectForKey(NSKeyedArchiveRootObjectKey) as! GameScene
archiver.finishDecoding()
return scene
} else {
return nil
}
}
}

Answer 1

Here, I made your code nicer and safe. This code (in theory) cannot crash whatever happens:
extension SKNode {
class func unarchiveFromFile(file : String) -> SKNode? {
guard let
path = NSBundle.mainBundle().pathForResource(file, ofType: "sks"),
sceneData = try? NSData(contentsOfFile: path, options: .DataReadingMappedIfSafe) else {
return nil
}
let archiver = NSKeyedUnarchiver(forReadingWithData: sceneData)
archiver.setClass(self.classForKeyedUnarchiver(), forClassName: "SKScene")
guard let scene = archiver.decodeObjectForKey(NSKeyedArchiveRootObjectKey) as? GameScene else {
return nil
}
archiver.finishDecoding()
return scene
}
}
If you don't know how the new error handling and guard works, you should check online.
Also if you really want to be fancy, you can use the new defer:
extension SKNode {
class func unarchiveFromFile(file : String) -> SKNode? {
guard let
path = NSBundle.mainBundle().pathForResource(file, ofType: "sks"),
sceneData = try? NSData(contentsOfFile: path, options: .DataReadingMappedIfSafe) else {
return nil
}
let archiver = NSKeyedUnarchiver(forReadingWithData: sceneData)
defer { archiver.finishDecoding() }
archiver.setClass(self.classForKeyedUnarchiver(), forClassName: "SKScene")
return archiver.decodeObjectForKey(NSKeyedArchiveRootObjectKey) as? GameScene
}
}

Answer 2

In swift 2.0 you have to manage errors thrown:
do {
var sceneData = try NSData(contentsOfFile: path, options: .DataReadingMappedIfSafe)
} catch let error as NSError {
// manage error case
}

Answer 3

There is no longer an NSData.init(contentsOfFile:options:error:) constructor. Most Cocoa calls that returned an error this way are now throwing. The new way to do what you've done here is:
var sceneData = try! NSData(contentsOfFile: path, options: .DataReadingMappedIfSafe)
Rather than getting back an optional and then force-unwrapping it, this uses a force-try to do the same thing. In both cases, this will crash if the read fails. Generally a normal try inside of a do/catch is preferred (just like you generally should not force-unwrap optionals).

Answer 4

You need to download the new version of the Swift language book. Enums that consist of bits that should be combined are now represented as sets, not as integer values. Everything is nicely explained in Apple's documentation.
Reading release notes is also very, very useful. At this point in time, Apple doesn't have the slightest scruples to modify the language in a way that breaks existing code. You need to keep up with it yourself.