Iterating through an Enum in Swift 3.0

Question

I have a simple enum that I would like to iterate over. For this purpose, I\'ve adopted Sequence and IteratorProtocol as shown in the code below. BTW, this can be copy/paste

Answer 1

Iterated upon the solutions above, see below a protocol that can be implemented by enumerations to add the allValues sequence but also to allow the possibility to convert to and from string value.

Very convenient for String-like enumerations which need to support objective c (only int enumerations are allowed there).

public protocol ObjcEnumeration: LosslessStringConvertible, RawRepresentable where RawValue == Int {
    static var allValues: AnySequence { get }
}

public extension ObjcEnumeration {
    public static var allValues: AnySequence {
        return AnySequence {
            return IntegerEnumIterator()
        }
    }

    public init?(_ description: String) {
        guard let enumValue = Self.allValues.first(where: { $0.description == description }) else {
            return nil
        }
        self.init(rawValue: enumValue.rawValue)
    }

    public var description: String {
        return String(describing: self)
    }
}

fileprivate struct IntegerEnumIterator: IteratorProtocol where T.RawValue == Int {
    private var index = 0
    mutating func next() -> T? {
        defer {
            index += 1
        }
        return T(rawValue: index)
    }
}

For a concrete example:

@objc
enum Fruit: Int, ObjcEnumeration {
    case apple, orange, pear
}

Now you can do:

for fruit in Fruit.allValues {

    //Prints: "apple", "orange", "pear"
    print("Fruit: \(fruit.description)")

    if let otherFruit = Fruit(fruit.description), fruit == otherFruit {
        print("Fruit could be constructed successfully from its description!")
    }
}