Swift Programming: The Big Nerd Ranch Guide, 3rd Edition

Optional Binding

Optional binding is a useful pattern to detect whether an optional contains a value. If there is a value, you assign it to a temporary constant or variable and make it available within a conditional’s first branch of execution. This can make your code more concise while also retaining its expressive nature. Here is the basic syntax:

    if let temporaryConstant = anOptional {
        // Do something with temporaryConstant
     } else {
        // There was no value in anOptional - anOptional is nil
    }

With this syntax in hand, refactor the example above to use optional binding.

Example 9.6. Optional binding

var errorCodeString: String?                               nil
errorCodeString = "404"                                    "404"
if errorCodeString != nil {
    let theError = errorCodeString!
if let theError = errorCodeString ...