Optionals

Optionals:

which handles the absence of a value.

Ex: var perhapsStr: String?

The above declaration is equivalent to explicitly initializing it to nil which means no value −

var perhapsStr: String? = nil

var myString:String? = nil

if myString != nil {

   print(myString)

} else {

   print("myString has nil value")

}

Forced Unwrapping : just means putting an exclamation mark at the end of the variable.

Automatic Unwrapping : You can declare optional variables using exclamation mark instead of a question mark. 

Optional Binding : Use optional binding to find out whether an optional contains a value , and to make that value available as a temporary constant or variable. 

Ex: 

if let constantName = someOptional {

   statements

}

var myString:String?

myString = "Hello, Swift 4!"

if let yourString = myString {

   print("Your string has - \(yourString)")

} else {

   print("Your string does not have a value")

}

Output : Your string has - Hello, Swift 4!