optional-literal-gotcha.swift

import UIKit

let nonOptionalVar: [String] = ["a", "b", "c"]
let optionalVar:String? = "jimmy"

// this compiles OK with import UIKit present
let ex1: [String: AnyObject] = ["key" : nonOptionalVar, "notherkey": ["content": optionalVar!]]

// Here we forget the ! character that unwraps the optional
// error: contextual type 'AnyObject' cannot be used with dictionary literal
let ex2: [String: AnyObject] = ["key" : nonOptionalVar, "notherkey": ["content": optionalVar]]

/*
 If we omit import UIKit both both cases error with a different message
 
 error: value of type '[String]' does not conform to expected dictionary value type 'AnyObject'
 
 [Sratches head]
*/