The supplementary Swift Playground to Swift 101 - Optionals.
/*:
# Swift 101 - nil
https://medium.com/pretty-swifty/optionals-b8d1e6bcddd
Today I’ll be blogging about another fundamental concept in Swift — Optional variables.
*/
// The following variables are all optional
var optionalInt: Int?
var optionalBool: Bool?
var optionalString: String?
// Uncomment the next line to how optional variables must not be declared `let`
//let optionalLetString: String?