JSONType.swift

// overloading on function return values to 
// enable destructuring a JSON-like type 

import Foundation

enum JSONType {
  case JBool(Bool)
  case JNumber(Int)
  case JString(String)
}

extension JSONType {
  func value() -> Bool? {
    guard case let .JBool(v) = self else { return nil }
    return v
  }

  func value() -> Int? {
    guard case let .JNumber(v) = self else { return nil }
    return v
  }

  func value() -> String? {
    guard case let .JString(v) = self else { return nil }
    return v
  }
}

let jString:JSONType = JSONType.JString("hello")

if let s:String = jString.value() {
  print("found a string")
}
else {
  print("did not find a string")
}

if let s:Int = jString.value() {
  print("found a string")
}
else {
  print("did not find a string")
}