//
// Swift 3, Optional
//

// Defining
let possibleNumber = "123"
let convertedNumber = possibleNumber.toInt() // convertedNumber is inferred to be of type 'Int?' or 'Optional<Int>"


// Nil
var serverResponseCode: Int? = 404 // serverResponseCode contains an actual Int value of 404
serverResponseCode = nil           // serverResponseCode now contains no value


// if Statements and Forced Unwrapping
if convertedNumber != nil {
    println("convertedNumber contains some integer value.")
}
// prints "convertedNumber contains some integer value."


// Optional Binding
if let actualNumber = possibleNumber.toInt() {
    println("\'\(possibleNumber)\' has an integer value of \(actualNumber)")
} else {
    println("\'\(possibleNumber)\' could not be converted to an integer")
}
// prints "'123' has an integer value of 123"


// Implicitly Unwrapped Optionals
let possibleString: String? = "An optional string."
let forcedString: String = possibleString! // requires an exclamation mark

let assumedString: String! = "An implicitly unwrapped optional string."
let implicitString: String = assumedString // no need for an exclamation mark


// Nil-Coalescing Operator (Optional<AType> ?? AType)
let notOptionalString = possibleString ?? "default value"