JSON Parser

gistfile1.swift

import Foundation

public class JSON: Printable {
    private let object: JSONObject
    init(_ object: AnyObject?) {
        self.object = JSONObject.parse(object)
    }
    private init(_ object: JSONObject) {
        self.object = object
    }
    private class var error: JSON { return JSON(.Err(JSONObject.parseError)) }
    
    subscript(k: String) -> JSON {
        switch self.object {
        case .Obj(let obj) where obj[k] != nil: return JSON(obj[k]!)
        default: return JSON.error
        }
    }
    subscript(n: Int) -> JSON {
        switch self.object {
        case .Arr(let arr): return JSON(arr[n])
        default: return JSON.error
        }
    }
    var string: String {
        switch self.object {
        case .Str(let str): return str
        default: abort()
        }
    }
    var number: NSNumber {
        switch self.object {
        case .Num(let num): return num
        default: abort()
        }
    }
    
    public var description: String { return "JSON(\(object))" }
    
    private enum JSONObject: Printable {
        case Obj([String: JSONObject])
        case Arr([JSONObject])
        case Str(String)
        case Num(NSNumber)
        case Null
        case Err(NSError)

        static var parseError: NSError {
            return NSError(domain: "JSONObject parse error", code: -100, userInfo: nil)
        }

        static func parse(JSON: AnyObject?) -> JSONObject {
            switch JSON {
            case let obj as [String: AnyObject]:
                var object: [String: JSONObject] = [:]
                map(obj) { object[$0] = self.parse($1) }
                return .Obj(object)
            case let arr as [AnyObject]: return .Arr(arr.map { self.parse($0) })
            case let str as String: return .Str(str)
            case let num as NSNumber: return .Num(num)
            case let null as NSNull: return .Null
            default: return .Err(parseError)
            }
        }

        private var description: String {
            switch self {
            case .Obj(let obj): return "Obj(\(obj))"
            case .Arr(let arr): return "Arr(\(arr))"
            case .Str(let str): return "Str(\(str))"
            case .Num(let num): return "Num(\(num))"
            case .Null: return "Null"
            case .Err(let e): return "Err\(e)"
            default: "abon"
            }
        }

    }
}

let obj = [
    "Alfa":    ["age": 20, "gender": "male"],
    "Bravo":   ["age": 21, "gender": "male"],
    "Charlie": ["age": 23, "gender": "male"],
]
let json = JSON(obj)
json["Alfa"]["age"].number
json["Bravo"]["age"].number
json["Charlie"]["age"].number