Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS Swift 2.0 Enumerations and Optionals Introduction to Enumerations Enum Methods

Brad Forsyth
Brad Forsyth
7,623 Points
Posted by Brad Forsyth
Brad Forsyth
7,623 Points

Why do I need a default case in this situation?

So in previous videos, such as with the ColorComponents enum, when Pasan wrote the switch statement in the function, he didn't use or even need a default case because every case in the enum was used in the switch statement. I tried that here, but it still says I need a default case. Why do I need it here, but we didn't need it in the ColorComponents enum?

buttons.swift 
import Foundation

enum UIBarButtonStyle {
    case Done
    case Plain
    case Bordered
}

class UIBarButtonItem {

    var title: String?
    let style: UIBarButtonStyle
    var target: AnyObject?
    var action: Selector

    init(title: String?, style: UIBarButtonStyle, target: AnyObject?, action: Selector) {
        self.title = title
        self.style = style
        self.target = target
        self.action = action
    }
}
enums.swift 
enum Button {
    case Done(String)
    case Edit(String)

    func toUIBarButtonItem() -> UIBarButtonItem {
        switch self {
        case Done("Done"):
            return UIBarButtonItem(title: "Done", style: .Done, target: nil, action: nil)
        case Edit("Edit"):
            return UIBarButtonItem(title: "Edit", style: .Plain, target: nil, action: nil)
        default:
            return UIBarButtonItem(title: "Default", style: .Bordered, target: nil, action: nil)
        }
    }
}

let done = Button.Done("Done")
let doneButton = done.toUIBarButtonItem()

1 Answer

Steven Deutsch
Steven Deutsch
21,046 Points
Steven Deutsch
Steven Deutsch
21,046 Points

Hey Brad Forsyth,

You need the default case because your switch is not exhaustive. You are checking for the cases where those enum members have the specific titles of "Done" or "Edit". It's possible for another Done button to exist with a title of "Finished" for example. If you want to remove the default case, you need to extract the associated values using a local constant:

enum Button {
    case Done(String)
    case Edit(String)

    func toUIBarButtonItem() -> UIBarButtonItem {
        switch self {
        // Now our switch will match these button types with any String associated value
        case Done(let title):
            return UIBarButtonItem(title: title, style: .Done, target: nil, action: nil)
        case Edit(let title):
            return UIBarButtonItem(title: title, style: .Plain, target: nil, action: nil)
        }
    }
}

let done = Button.Done("Done")
let doneButton = done.toUIBarButtonItem()

Hope this helps! Good Luck!