Unwrapping with guard

An alternative to if let is guard let, which also unwraps optionals. guard let will unwrap an optional for you, but if it finds nil inside it expects you to exit the function, loop, or condition you used it in.

However, the major difference between if let and guard let is that your unwrapped optional remains usable after the guard code.

Let’s try it out with a greet() function. This will accept an optional string as its only parameter and try to unwrap it, but if there’s nothing inside it will print a message and exit. Because optionals unwrapped using guard let stay around after the guard finishes, we can print the unwrapped string at the end of the function:

func greet(_ name: String?) {
    guard let unwrapped = name else {
        print("You didn't provide a name!")
        return
    }

    print("Hello, \(unwrapped)!")
}

Using guard let lets you deal with problems at the start of your functions, then exit immediately. This means the rest of your function is the happy path – the path your code takes if everything is correct.