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iOS Enumerations and Optionals in Swift Introduction to Enumerations Enum Methods

Posted by Lokesh Gnanasekhar
Lokesh Gnanasekhar
1,840 Points

Showing compiler errors and nothing is previewed in preview window

Every appears correct in the playground , but still showing errors. Tried adding UIKit too but still same issue

buttons.swift 
// Example of UIBarButtonItem instance
// let someButton = UIBarButtonItem(title: "A Title", style: .plain, target: nil, action: nil)


enum BarButton {
    case done(title: String)
    case edit(title: String)

    func button() -> UIBarButtonItem {
      switch self {
        case .done(let title): let doneButton = UIBarButtonItem(title: "A Title", style: .done, target: nil, action: nil)
                    return doneButton
        case .edit(let title): let editButton = UIBarButtonItem(title: "A Title", style: .plain, target: nil, action: nil)
                    return editButton
      }
    }
}
let button = BarButton.done(title: "Save").button()

4 Answers

Nico Schmidt
Nico Schmidt
12,781 Points
Nico Schmidt
Nico Schmidt
12,781 Points

You are quite right. The script is quite strict. So it should look like that.

let done = BarButton.done(title: "Save")
let button = done.button()
Lokesh Gnanasekhar
Lokesh Gnanasekhar
1,840 Points

Thank you so much. Issue resolved. The editor is too strict .

Nico Schmidt
Nico Schmidt
12,781 Points
Nico Schmidt
Nico Schmidt
12,781 Points

Hint: You want to bind the associated value of title to the correct enum member. Currently you use „A Title“.

Lokesh Gnanasekhar
Lokesh Gnanasekhar
1,840 Points

I Corrected to title instead of "A Title" But still it says compiler error. But in xcode playground its not showing any error

Nico Schmidt
Nico Schmidt
12,781 Points
Nico Schmidt
Nico Schmidt
12,781 Points

You can now return directly the UIButtonItem without declaring a constant.

Lokesh Gnanasekhar
Lokesh Gnanasekhar
1,840 Points

On returning it directly its throwing error like this - Bummer! Make sure you're assigning the enum value to a constant named done. But as per task i should assign it to a "button" constant .

Task : Next, add a method to the enum named button that returns an instance of the class UIBarButtonItem configured properly. An example of how to create an instance for this task is shown in the comments below. Use the same initializer.

In the method, using the associated values as titles for the button, return a button with style UIBarButtonStyle.done for the done member of the BarButton enum. Similarly for the edit member, return a UIBarButtonItem instance with the style set to UIBarButtonStyle.plain.

In both cases you can pass nil for target and action. Once you have a method, call it on the value we created in the previous task and assign it to a constant named button.

Solution:

enum BarButton { case done(title: String) case edit(title: String)

func button() -> UIBarButtonItem {
  switch self {
    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 button = BarButton.done(title: "Save").button()