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Once you’ve created an optional, you’ll want to be able to access the value inside. However, if you just try to use the optional, you will get a compile-time error:

var a = 4 var b: Int? = 3 let sum = a + b // ERROR: Value of optional type 'Int?' must be unwrapped to a value of type 'Int'

The easiest way to wrap an optional is using the ! operator. This process is called force unwrapping and will break open the optional and let you use the underlying value:

var a = 4 var b: Int? = 3 let sum = a + b! print(sum) // Prints 7

But be careful! If the underlying value is nil, your program will crash:

var a = 4 var b: Int? = nil let sum = a + b! // Fatal error: Unexpectedly found nil while unwrapping an Optional value print(sum)

Make sure to only use the ! operator if you are absolutely sure that the value isn’t nil. To be safe, you can check using an if statement:

var a = 4 var b: Int? = nil if b != nil { let sum = a + b! print(sum) Prints 7 }

Instructions

1.

Define a variable flightDistance of type Int with a value of 1000, and a variable connectingFlightDistance of type Int? with a value of 2000.

2.

Write an if statement that checks if connectingFlightDistance is not nil.

3.

In the body of the if statement, define a constant totalFlightDistance assigned to the sum of flightDistance and connectingFlightDistance. Then, print the totalFlightDistance.

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