Declaring and using a bit field enum in Swift

Question

How should bit fields be declared and used in Swift?

Declaring an enum like this does work, but trying to OR 2 values together fails to compile:

enum         


        

Answer 1

Task

Get all flags from flags_combination. Each flag and flags_combination are integers. flags_combination = flag_1 | flags_2

Details

• Xcode 11.2.1 (11B500), Swift 5.1

Solution

import Foundation

protocol FlagPrototype: CaseIterable, RawRepresentable where RawValue == Int {}
extension FlagPrototype {
    init?(rawValue: Int) {
        for flag in Self.allCases where flag.rawValue == rawValue {
            self = flag
            return
        }
        return nil
    }
    static func all(from combination: Int) -> [Self] {
        return Self.allCases.filter { return combination | $0.rawValue == combination }
    }
}

Usage

enum Flag { case one, two, three }
extension Flag: FlagPrototype {
    var rawValue: Int {
        switch self {
        case .one: return 0x1
        case .two: return 0x2
        case .three: return 0x4
        }
    }
}

var flags = Flag.two.rawValue | Flag.three.rawValue
let selectedFlags = Flag.all(from: flags)
print(selectedFlags)
if selectedFlags == [.two, .three] { print("two | three") }