Swift Programming: The Big Nerd Ranch Guide

Optional Binding

Optional binding is a useful pattern to detect whether an optional contains a value. If there is a value, then you can 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; i.e., anOptional is nil
}

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

Listing 8.5  Optional binding

import Cocoa

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