Introduction to Optionals (Part 2)

The second part of optionals! I get Optional Binding so we'll see what we have next...

Downsides to using If Let

Optional binding is used with the if let. The example Pasan gives highlights a couple of flaws - what if we don't have the data? Well, we would have to use else and nil.

struct Friend {

    

    let name: String

    let age: String

    let address: String?

}

func new(friendDictionary: [String: String]) -> Friend? {

    

    let name = friendDictionary["name"]

    

    if name == nil {

        

        return nil

    }

    

    let address = friendDictionary["address"]

}

The issue here is we would have to return the values using ! which is not recommended. The main point Pasan makes is that optional binding is laborious but it was necessary in Swift 1. From Swift 2 onwards there is supposed to be a better way....

Early Exits Using Guard

There is a Guard statement....

func newFriend(friendDictionary: [String: String]) -> Friend? {

    guard let name = friendDictioary["name"], let age = friendDictionary["age"] {

        

        else return nil

    }

    

    let address = friendDictionary["address"]

    

    return Friend(name: name, age: age, address: address)

So there is no need for 'nested' code - brackets within brackets etc. 

Challenge - had to use help to figure this out. Not too sure about the use of the guard statement - need more practice with this!

Recap

You have to be prepared for 'nil' to be returned - otherwise the program will crash. 

In Swift, you can use ? to make a clear optional type, if a value can return nil. 

If the type is not an optional, the compiler will warn you - more safety with the code!

We have to unwrap (a type of enum) - using if/let - an expression to evaluate if an optional is returned. This is laborious and has nested values though. 

Guard statement is preferable - can lead to an 'early exit'. Else clause is used inside. 

Forced unwrapping - not use this as a valid option for now!

Optionals is something that I've always found difficult but I honestly feel like I can see the purpose of them now. Let's say you have a database of values but one of them may not contain anything, nil has to be an option. The whole unwrapping process is long-winded so I will need some practice with that at some point. The next set of videos are to do with Objects and Optionals. Once I've done that, then that's the enum/optional course complete. Definitely the hardest so far, so I know that it is something to get more practice with when I'm using the Udemy courses.