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Enum with associated value conforming to CaseIterable, RawRepresentable

Tags:

enums

swift

I'm trying to make enum with associated value conform to CaseIterable, RawRepresentable. I'm fine with some default values for associated values when initializing by rawValue.

enum GenresAssociated: CaseIterable, RawRepresentable, Equatable {
    case unknown(String)
    case blues(String)
    case classical(String)
    // Implementing CaseIterable
    typealias AllCases = [GenresAssociated]
    // Enums can have no storage, but the class they are in CAN. Note 'static' in declaration
    static var allCases: [GenresAssociated] = [.unknown(""), .blues(""), .classical("")]


    typealias RawValue = Int
    var rawValue: Int {

        // MARK: This causes a crash for unknown reason
        return GenresAssociated.allCases.firstIndex(where: {  if case self = $0 { return true } else { return false } } ) ?? 0
    }
    init?(rawValue: Int) {
        guard GenresAssociated.allCases.indices.contains(rawValue) else { return nil }
        self = GenresAssociated.allCases[rawValue]
    }
}

Is there any way to make it without switching manually by all the cases, i.e. without such code:

    typealias RawValue = Int
    var rawValue: Int {
        switch self {
        case .unknown:
            return 0
        case .blues:
            return 1
        case .classical:
            return 2
        }
    }

What's notable is that very similar code works just fine, for example

enum EnumWithValue {
    case one(NSString!), two(NSString!), three(NSString!)
}

let arrayOfEnumsWithValues: [EnumWithValue] = [.one(nil), .two(nil), .three("Hey")]

if let index = arrayOfEnumsWithValues.firstIndex(where: { if case .two = $0 { return true }; return false }) {
    print(".two found at index \(index)") //prints ".two found at index 1"
}
like image 682
Paul B Avatar asked Mar 17 '19 21:03

Paul B


People also ask

Can you give useful examples of enum associated values?

For instance, you might describe a weather enum that lists sunny, windy, and rainy as cases, but has an associated value for cloudy so that you can store the cloud coverage. Or you might describe types of houses, with the number of bedrooms being an associated integer.

What is associated value in enum Swift?

This additional information is called an associated value, and it varies each time you use that case as a value in your code. You can define Swift enumerations to store associated values of any given type, and the value types can be different for each case of the enumeration if needed.

What is Rawrepresentable?

A type that can be converted to and from an associated raw value.

What is Caseiterable?

A type that provides a collection of all of its values.


1 Answers

I got it finally to work with Mirror!

var rawValue: Int {
    let selfCaseName = Mirror(reflecting: self).children.first!.label!

    return GenresAssociated.allCases.firstIndex(where: { (genre) in
        let switchingCaseName = Mirror(reflecting: genre).children.first!.label!

        return switchingCaseName == selfCaseName
    })!
}

Don't mind the force unwrapping, it is safe here.

like image 198
J. Doe Avatar answered Nov 06 '22 22:11

J. Doe