Error-Handling in Swift

At link(http://stackoverflow.com/a/24185109), he shows three ways to handle errors.
1. using enum

enum ServerResponse {
    case Result(String, String)
    case Error(String)
}

let success = ServerResponse.Result("6:00 am", "8:09 pm")
let failure = ServerResponse.Error("Out of cheese.")

switch success {
case let .Result(sunrise, sunset):
    let serverResponse = "Sunrise is at \(sunrise) and sunset is at \(sunset)."
case let .Error(error):
    let serverResponse = "Failure...  \(error)"
}

2. use option chaining 

let myLength = myObject.length?
let myChar = myObject.characterAtIndex?(5)
if let fifthCharacter = myObject.characterAtIndex(5) {
    println("Found \(fifthCharacter) at index 5")
}

3. use cocoa error pattern from Objective-C (NSError Object)

var writeError : NSError?
let written = myString.writeToFile(path, atomically: false,
    encoding: NSUTF8StringEncoding,
    error: &writeError)
if !written {
    if let error = writeError {
        println("write failure: \(error.localizedDescription)")
    }
}

or, the snipcode at http://stackoverflow.com/a/26749528

func write(path: String)(#error: NSErrorPointer) -> Bool { // Useful to curry error parameter for retrying (see below)!
    return "Hello!".writeToFile(path, atomically: false, encoding: NSUTF8StringEncoding, error: error)
}

var writeError: NSError?
let written = write("~/Error1")(error: &writeError)
if !written {
    println("write failure 1: \(writeError!.localizedDescription)")
    // assert(false) // Terminate program
}

At other links, you can see some ways to handle.
http://blog.scottlogic.com/2015/01/27/swift-exception-handling.html

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