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iOS Swift 2.0 Enumerations and Optionals Introduction to Enumerations Enums with Associated Values

Ryan Maneo
Ryan Maneo
4,342 Points
Posted by Ryan Maneo
Ryan Maneo
4,342 Points

Where did I mess up?

As you can see, I tried several ways of returning a String, and the instance just won't work.

enums.swift 
enum MobilePhone /* I tried this */ -> String {
    // I tried all 4 options I could think of too
    case iPhone: return String
    case Android return: String
    case Blackberry: String
    case WindowsPhone -> String

    // Including this
    return String
}

let iPhone = MobilePhone(iPhone: "6S")

2 Answers

Ryan Anderson
Ryan Anderson
2,920 Points
Ryan Anderson
Ryan Anderson
2,920 Points

When you're using an enum, you need to specify that you using a specific enum, and a specific case within the enum because the cases contain the information - the enum is kind of the container. The container can do some more advanced things, and it can specify what goes in the container, but it doesn't specifically have a value of its own.

So, let phone = MobilePhone doesn't really tell us anything, so you'll get an error. It's like saying direction = All the Directions instead of direction = north.

The stuff that comes after the dot is the "argument." So you're saying let this thing = the enumeration "MobilePhone" and within that, the case "iPhone." Kind of like a dropdown menu where you choose MobilePhone, and then select iPhone from the list. You can't just select MobilePhone, because it's just a container.

There is a chance at some point you'd want to refer to the type case with MobilePhone.self, but I wouldn't worry about that for now.

Hope that helps.

Ryan Maneo
Ryan Maneo
4,342 Points
Ryan Maneo
Ryan Maneo
4,342 Points

Great explanation... definitely helped. Thanks!

Ryan Anderson
Ryan Anderson
2,920 Points
Ryan Anderson
Ryan Anderson
2,920 Points

You're close - the syntax for an associated value is:

case Thing(Type)

In this case, you want to declare an associated value of type String for the iPhone case.

enum MobilePhone {
    case iPhone(String)
    case Android
    case Blackberry
    case WindowsPhone
}

Then, to assign it to a constant, you need to add the string after the instance of MobilePhone with case iPhone:

let iPhone = MobilePhone.iPhone("6S")

Hope that helps.

Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points
Martin Wildfeuer
Martin Wildfeuer
Courses Plus Student 11,071 Points

Just to follow up on this: the syntax for creating an enum that returns a String (or any other type) would be:

enum MobilePhone: String {
    case iPhone = "iPhone"
    case Android = "Android"
    ...
}

let iPhone = MobilePhone.iPhone.rawValue // "iPhone"

Not related to the challenge and not a solution ;)

Ryan Maneo
Ryan Maneo
4,342 Points
Ryan Maneo
Ryan Maneo
4,342 Points

Why dot notation? I thought you would call an instance of it... really confused now in general. Thanks for explaining though.