SafeJSON.playground

import Cocoa
import Foundation

let jsonString = "{\"username\": \"josh\"}"
let data = jsonString.dataUsingEncoding(NSUTF8StringEncoding)!

// UNSAFE JSON PARSING

//var jsonError: NSError?
//let json = NSJSONSerialization.JSONObjectWithData(data, options: nil, error: &jsonError) as NSDictionary
//
//if let unwrappedError = jsonError {
//    println("json error: \(unwrappedError)")
//} else {
//    let username = json.valueForKeyPath("username") as String
//    println("username: \(username)")
//}

// SAFE JSON PARSING

var jsonError: NSError?
if let json = NSJSONSerialization.JSONObjectWithData(data, options: nil, error: &jsonError) as? [String: AnyObject] {
    if let unwrappedError = jsonError {
        println("json error: \(unwrappedError)")
    } else {
        if let username = json["username"] as? String {
            println("username: \(username)")
        }
    }
}

Hello, in "safe json parsing" section: should not you move out jsonError from successful "if let" as below?

if let json = NSJSONSerialization.JSONObjectWithData(data, options: nil, error: &jsonError) as? [String: AnyObject] {
if let username = json["username"] as? String {
println("username: (username)")
}
} else {
if let unwrappedError = jsonError {
println("json error: (unwrappedError)")
}
}