如何在 Swift 中对具有关联值的枚举数组进行排序？

Question

First question on StackOverflow… Please be kind. :)

I have an array of enums with associated values which I would like to sort chronological. One of these values contains a date (as a String) which gets displayed and should be used for sorting.

Here is what it looks like at the moment:

enum cellType {
    case standard(text: String, icon: UIImage, hasChildren: Bool, reference: String)
    case detailed(text: String, secondaryText: String, icon: UIImage, hasChildren: Bool, reference: String)

    var identifier: String {
        switch self {
        case .standard: return "standardCell"
        case .detailed: return "detailedCell"
        }
    }
}

var cellData: [cellType]

Then the cellData gets populated with some cellType s. The value for secondaryText contains the date and it looks like this:

print(cellData) 

// [
//    AppIdentifier.cellType.detailed(text: "Title A", secondaryText: "2017-10-20T10:04:00.000+02:00", icon: <UIImage: 0x60c0002a6660>, {12, 21}, hasChildren: false, reference: "40693"),
//    AppIdentifier.cellType.detailed(text: "Title B", secondaryText: "2016-12-14T10:04:00.000+02:00", icon: <UIImage: 0x60c0002a6660>, {12, 21}, hasChildren: false, reference: "40632")
//    AppIdentifier.cellType.detailed(text: "Title C", secondaryText: "2017-10-20T10:07:00.000+02:00", icon: <UIImage: 0x60c0002a6660>, {12, 21}, hasChildren: false, reference: "40694"),
//    AppIdentifier.cellType.detailed(text: "Title D", secondaryText: "2017-11-16T10:34:00.000+02:00", icon: <UIImage: 0x60c0002a6660>, {12, 21}, hasChildren: false, reference: "40633"),
//    AppIdentifier.cellType.detailed(text: "Title E", secondaryText: "2017-10-19T10:12:00.000+02:00", icon: <UIImage: 0x60c0002a6660>, {12, 21}, hasChildren: false, reference: "40682"),
// ]

When I tried to sort the array, the following was apparently too simple:

var cellDataSorted = cellData.sorted(by: {$0.detailed.secondaryText < $1.detailed.secondaryText})

// Swift Compiler Error: enum element ’detailed’ cannot be referenced as an instance member

What would be the best way to sort this array? Thanks in advance!

Answer 1

(I am writing this on the phone, so.. fix the syntax if necessary)

Use following code within the sorted function:

if case .detailed(_, let date0, _, _, _) = $0, case .detailed(_, let date1, _, _, _) = $1 {
     return date0 < date1
} else {
    // One of them didn't have date (should never happen)
    return true
}

Your problem is, that you are accessing the parameters of the enum as if it was an instance of a class/struct.