Swift Optionals

Swift Optional is used at that place where variable can be nil. To set a variable as Optional, question mark is added to the type. For example,

    var optionalExample : Int?

Now by default optionalExample variable will have nil means no value.

    optionalExample = 5

Now optionalExample variable has a value 5.

You can assign nil to optional variable at any time using assignment operator. For example,

    optionalExample = nil

If there is possibility that value can nil then variable is automatically set to optional type. For example, initializing a variable with type conversion from String to Int. So there is possibility that there comes a String value that could not be converted to an integer. For example,

    let myValue =  "123"
    var  myNumber = Int(myValue)

So now myNumber is declared as Int? (optional Int) and it has currently value 123.

Forced Unwrapping

If you are sure that an optional definitely has a value then you can force unwrap it to use that value using exclamation mark after that constant or variable. For example,

    let defNumber : Int? = 345
    if(defNumber != nil)
    {
	    print(“Value : \(defNumber!)”)
    }

Note that "\( )" has been used to write a number in the String. It has nothing to do with Forced Unwrapping.

Optional Binding

Optional Binding is to find out that either optional has a value or not. If the optional has value only then if’s block of statements in curly brackets will be executed.

    if let myNumber =  myOptional
    {
    	// Set of statement to be executed if myOptional is not nil.
    }

Not that if myOptional is not nil then its value would be assigned to a temporary constant myNumber.