Swift Array, how to retrieve all elements in a nested enum from an array

Question

I'm trying to figure out a way to retrieve all elements in a nested enum from an array. The way I built my nested enum as follows:

enum ItemType: Hashable {
    case sword(Swords) 
    case shield(Shields)  
    case armor(Armors) 
}

enum Swords: String, CaseIterable {
    case Sabre = "Sabre"
    case Xiphos = "Xiphos"
    case Broadsword = "Broadsword"
}

enum Shields: String, CaseIterable {
    case Buckler = "Buckler"
    case HeaterShield = "Heater Shield"
    case KiteShiled = "Kite Shield"

}

enum Armors: String, CaseIterable {
    case StudArmor = "Stud Armor"
    case Chainmail = "Chainmail"
    case PlateArmor = "Plate Armor"
}

Now I have an array that contains some of the elements from the ItemType enum:

let loots: [ItemType] = [
    .sword(.Xiphos),
    .sword(.Broadsword), 
    .sword(.Sabre),
    .armor(.StudArmor), 
    .armor(.Chainmail),
    .shield(.Buckler), 
    .shield(.HeaterShield)
]

Is there a way to get all elements under ItemType.sword into another array? I'm thinking along the line of: (obviously it doesn't work)

let item = loots.first(where: {$0 == ItemType.sword})

How can I achieve my goal? Or do I have to reconstruct my Enums in a different way?

Please let me know.

Thank you in advance.

Does this answer your question? Filter array of items by enum property with associated value — HangarRash
– HangarRash, Commented Aug 20, 2023 at 0:45

Leo Dabus · Accepted Answer · 2023-08-20 04:48:32Z

0

You can add a computed property to your enum ItemType to check if it is a sword or not:

extension ItemType {
    var isSword: Bool {
        switch self {
        case .sword:
            return true
        default:
            return false
        }
    }
}

or if you prefer if case instead of switch:

extension ItemType {
    var isSword: Bool {
        if case .sword = self { return true }
        return false
    }
}

Them you can simply get the first item where isSword or filter them:

let item = loots.first(where: \.isSword) // sword(.Xiphos)

let items = loots.filter(\.isSword) // [{Xiphos}, {Broadsword}, {Sabre}]

Note that it is Swift naming convention to name all your enumeration cases starting with a lowercase letter.

edited Aug 20, 2023 at 4:48

answered Aug 20, 2023 at 0:58

Leo Dabus

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6 Comments

Bob Over a year ago

Thank you so much! This worked great. However, I do have a follow up question. How do I pass something like .isSword as a parameter? As in some cases where I might want to filter for ItemType.shield or ItemType.armor.

Leo Dabus Over a year ago

"How do I pass something like .isSword as a parameter?" Not sure what you mean but I guess you are asking how to pass it in a closure. where: \.isSword can also be written as { $0.isSword }. If you need isShield or isArmor you need to add those computed properties as well and filter { $0.isArmor || $0.isShield }. Another option is to create an isArmorOrShield property and use it as a keyPath syntax.

Bob Over a year ago

What I wanted is to call a func and pass in a parameter to be used as the criteria for array filter. Func filterItem(parameter) { let items = loots.filter(parameter)} Hope I made myself clear.

Leo Dabus Over a year ago

@Bob If you need a func you can add predicate: (ItemType) -> Bool to your method signature. func filterItem(predicate: (ItemType) -> Bool) and then loots.filter(predicate)

Bob Over a year ago

I've figured it out: Func filterItem(myFilter: @escaping (ItemType) -> Bool). This way, I can call it using: filterItem(myFilter: {$0.isArmor}). Thanks again for all your help!

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